IES-RP-7-2001

RP-7-01 ERRATA

If you, as a user of IESNA’s Recommended Practice for Industrial Lighting Facilities, believe you have located an error not covered by the following revisions, you should e-mail your information to Don Mennie at: [email protected] or send a letter to: Don Mennie, Technical Editor, IESNA, 120 Wall Street 17th Floor, New York, N Y 10005. Additions will be posted to this list as they become available. This errata list is also included with the published document (when purchased). It was posted to the IESNA web page on July 20,2004.

Please confiie your comments to specific typographical errors or misstatements of fact in the document’s text and/or graphics. Do not attempt general revisions of RP-7-0 1.

General Comment: Rest assured that IESNA does know how to spell “luminaires,” but unfortunately, thanks to a typesetting automatic correction function, the computer thought it knew better! Please note that “luminaries” throughout the document should read “luminaires.”

Page I I , Figure 6: The headers for the three CIE Specification columns in Figure 6 should read “x,” and <<y??

Pages 34-36, Figure 20: The references within Figure 20 to a Figure 19 (parts “a” through “o”) actually refer to Figure 19-15 in the IESNA Lighting Handbook, 9th Edition. (Figure 19 in RP-7-01 is a small black-and-white photo on Page 33.) Also, the “Luminaire Type” designations used in one column running throughout Figure 20 are taken from Figure 19-15. Therefore, in the interests of convenience and completeness, Figure 19- 15 (from the Handbook) is reproduced below:

1

Lo o o O ] s-IV 9

Figure 19-15. Typical configurations of supplementary lighting luminaire types.

Page 36, Figure 20: Under ?B. TRANSLUCENT MATERIAL? two of the figure references in the right-hand ?Luminaire Location? column are broken, with a portion positioned flush left in the ?General Characteristics?co1umn.

Page 71, Annex C: The equations for FCR and CCR appearing at the top of the left-hand column actually belong on page 72 in the left-hand column, under the second paragraph.

Page 71, Annex C: Text and equations are missing from the bottom of the left-hand column (this error continues to the very top of the right-hand column) in the paragraph that begins ?TO find the RCR,. . .? The complete and correct text is:

To find the RCR, either of the following equations can be used:

Vertical Surface Area (VSA) Horizontal Surface Area (HSA)

RCR = 5 X

where: VSA = the sum of the vertical surfaces within the room cavity. This is the sum of the wall areas

above the working plane and below the luminaires.

HAS = the sum of the working plane and the luminaire plane areas.

or:

Room Cavity Height X (Lenght + Width) Length X Width RCR =5X

Correct text resumes on page 71 with the beginning of the first full paragraph in the right-hand column (?The areas in the first equation are.. ..?).

3

ERRATA RP-7-01

1. Rest assured that IESNA does know how to spell “luiiiinaires,” bui unfortunately, thanks to a typesetting automatic correction function, the computer thought i t knew better! Please note that “luminaries” throughout the document should read “luminaires.”

2. Header for Figure 6, page 1 1, CIE Specification columns should read “x,” “y,” and “Y”

3. Figure 20, pages 34 -26, is reproduced from the IESNA Handbook, 9‘h Edition, 2000. The references to Figures (some misaligned) throughout are to Figures in the Handbook.

4. Annex C has some misplaced equations. On page 7 I , left columnl equations foi- I’CR and CCR belong on pase 72 following the second paragraph. left column.

h4issing annescs on page 7 1. left coliiii~ii. Test should i-ead:

P’ei~icuI Sin:fcrce Ar-eu (J’SA) Horizoritul Surjuce Areu ( H S A )

RCR = 5.y

where: VSA = the sum of the vertical surfaces within the room cavity. This is the sum of the wall areas above the working plane and below the luminaires.

HSA = the sum of the working plane and the luminaire plane areas

Or:

Room Cavity Height x (Length + Width) Length x Width

The areas in the first equation.. . . . . . . .etc. Right column, page 7 1.

RCR = 5x

ANSUIESNA RP-7-01

Recommended Practice for

Lighting Industrial Facilities

Publication of this Committee Report has been approved by the IESNA. Suggestions for revisions should be directed to the IESNA.

Prepared by: The IESNA Industrial Lighting Committee

Cover photo courtesy of Keene-Widelite Division of Canlyte

ANSI / IESNA RP-7-01

Copyright 200 7 by the Illuminating Engineering Society of North America.

Approved by the IESNA Board of Directors, August 4, 2007, as a Transaction of the Illuminating Engineering Society of North America.

Approved July 26, 2001 by the American National Standards Institute, Inc.

All rights reserved. No part of this publication may be reproduced in any form, in any electronic retrieval system or otherwise, without prior written permission of the IESNA.

Published by the Illuminating Engineering Society of North America, 120 Wall Street, New York, New York 10005.

IESNA Standards and Guides are developed through committee consensus and produced by the IESNA Office in New York. Careful attention is given to style and accuracy. If any errors are noted in this document, please forward them to Rita Harrold, Director Educational and Technical Development, at the above address for verification and correction. The IESNA welcomes and urges feedback and comments.

ISBN #O-87995-176-1

Printed in the United States of America.


ANSMESNA RP-7-01 Recommended Practice on Industrial Lighting

Prepared by the IESNA Industrial Lighting Committee

RP Task Force: Diarmuid McSweeney, FIES Chair

C. Amick D. DeGrazio R. Knott S. Mishky D. Paulin M. Rhodes G. Schaefer

Industrial Lighting Committee William Busch, Chair 7994-99 Diarmuid McSweeney, FIES Chair 2000 -

C. Amick, FIES P. Belding W. Busch K. Chen* D. DeGrazio F. Dickey D. Duzyk* J. Engle* J. Fetters* D. Finch J. Fischer J. Huebner G. Imine* V. Jones

R. Knott* W. Lane* P. Lanphere* S. Mishky M. Packer* D. Paulin M. Rhodes G. Schaefer W. Smelser* S. Thomas R. Topalova J. Vlah* R. Weber*

*Advisory

Special recognition to F, Dickey for his work on the first draft of the revision of this standard and to P. Boyce, FIES and R. Mistrick, FIES for their contributions.

DEDICATION

The IESNA Industrial lighting Committee would like it noted that Charles Amick

contributed greatly to the development of this document. The committee, therefore,

dedicates this recommended practice to the late Charles Amick.


CONTENTS

Forward ..................................................................................................................................................................... 1

1.0 INTRODUCTION .............................................................................................................................................. 1

2.0 LIGHTING THE INDUSTRIAL ENVIRONMENT ............................................................................................ 1

2.2 IESNA Lighting Design Guide .......................................................................................................... 2 2.1 General Design Considerations for Lighting Industrial Areas ..................................................... 1

3.0 QUALITY OF LIGHTING IN INDUSTRIAL FACILITIES ................................................................................ 2 3.1 Luminance and Luminance Ratios ................................................................................................... 2 3.2 Modeling of Objects ............................................................................................................................ 6 3.3 Glare and Visual Discomfort ............................................................................................................ 6 3.4 Material Characteristics ...................................................................................................................... 7 3.5 Shadows ............................................................................................................................................... 8 3.6 SourcNasWEye Geometry ................................................................................................................ 8 3.7 Task Visibility-Flicker and Strobe .................................................................................................... 9 3.8 Color Rendering (CRI) ...................................................................................................................... 10

3.8.1 Color Rendering Index .......................................................................................................... 10 3.8.2 Safety Colors ......................................................................................................................... 10

3.9 Daylight Integration and Control ..................................................................................................... 10

4.0 QUANTITY OF LIGHTING IN INDUSTRIAL FACILITIES ........................................................................... 11 4.1 Illuminance - Horizontal, Vertical and Intermediate Planes ........................................................ 11

4.1.1 Horizontal Illuminance ........................................................................................................... 11 4.1.2 Vertical Illuminance ............................................................................................................... 12

4.2 Initial and Maintained Illuminance .................................................................................................. 12 4.3 Lighting System Maintenance ......................................................................................................... 13

5.0 GENERAL LIGHTING EQUIPMENT ............................................................................................................ 13 5.1 Fluorescent Systems ........................................................................................................................ 13

5.1.1 Source Characteristics .......................................................................................................... 13 5.1.2 Fluorescent Luminaire Characteristics/Performance ........................................................... 15

5.2 High Intensity Discharge Lighting Systems .................................................................................. 15 5.2.1 Metal Halide Lamps .............................................................................................................. 15

5.2.1.1 Pulse-Start and Ceramic Metal-Halide Lamps ................................................ 17 5.2.2 High Pressure Sodium (HPS) Lamps ................................................................................. 17 5.2.3 Luminaire Selection .............................................................................................................. 17

5.2.3.1 High-Bay Luminaries ......................................................................................... 18 5.2.3.2 Low-Bay Luminaries .......................................................................................... 18 5.2.3.3 Other Luminaire Types ..................................................................................... 18

6.0 BALLAST ISSUES-GENERAL ..................................................................................................................... 18 6.1 Fluorescent Ballast Issues ............................................................................................................. 19

6.1.1 Ballast Circuitry ........................................................................................... .......................... 19 6.1.2 Electromagnetic Ballasts ....................................................................................................... 20 6.1.3 Electronic Ballasts ................................................................................................................. 20 6.1.4 Instant Start Ballasts ............................................................................................................. 20 6.1.5 Rapid Start Ballasts ............................................................................................................. 21

6.1.7 Dimming and Two-Level Switching Ballasts ........................................................................ 21 6.1.8 General Ballast Requirements .............................................................................................. 21

6.1.6 Compact Fluorescent Ballasts .............................................................................................. 21


6.2 High Intensity Discharge (HID) Ballast Issues .............................................................................. 21 6.2.1 Ignitor ..................................................................................................................................... 23 6.2.2 Metal-Halide Ballasts ........................................................................................................... 23 6.2.3 High Pressure Sodium Ballasts ............................................................................................ 23

6.2.3.1 6.2.3.2 Lag or Reactor Ballast ....................................................................................... 23 6.2.3.3 Lead Circuit Ballast ............................................................................................ 24

6.2.4 Other HID Ballasts ................................................................................................................ 24

Magnetic Regulator or Constant-Wattage Autotransformer (CWA) Ballast ..... 23

7.0 DISTRIBUTION MODES ................................................................................................................................ 24 7.1 General Luminaire Characteristics and Performance ................................................................ 24

7.2.1 Electrical ................................................................................................................................ 24 7.3 Luminaire Classifications ............................................................................................................... 24

7.2 Operating Considerations ................................................................................................................ 24

8.0

9.0

10.0

11 .o

12.0

13.0

14.0

BUILDING CONSTRUCTION FEATURES THAT INFLUENCE LUMINAIRE SELECTION AND LUMINAIRE PLACEMENT ........................................................... 26

LIGHTING SYSTEM ECONOMIC ANALYSIS ............................................................................................. 27

SPECIAL CONSIDERATION FACTORS ...................................................................................................... 29 Lighting and Space Conditioning ................................................................................................... 29 10.1

10.2 Classified Areas ................................................................................................................................ 29 10.3 High Humidity or Corrosive Atmospheres .................................................................................... 30 10.4 High Ambient Temperatures ............................................................................................................ 30 10.5 Low Ambient Temperatures ............................................................................................................. 30 10.6 Clean Rooms ..................................................................................................................................... 30 10.7 Food and Drug Processing .............................................................................................................. 31

GENERAL LIGHTING ................................................................................................................................... 31

SUPPLEMENTARY TASK LIGHTING .......................................................................................................... 31 12.1 Luminaries for Supplementary Task Lighting ............................................................................. 32

.l 2.2 Portable Luminaries ......................................................................................................................... 32 12.3 Classification of Visual Tasks and Lighting Techniques ............................................................. 33

SPECIAL EFFECTS AND TECHNIQUES ................................................................................................... 33 13.1 Color Contrast .................................................................................................................................. 33 13.2 Inspection Techniques .................................................................................................................... 33

EMERGENCY. SAFETY AND SECURITY LIGHTING ............................................................................... 36 14.1 Emergency Lighting ........................................................................................................................ 36 14.2 Safety Lighting ................................................................................................................................. 37 14.3 Security Lighting .......................................................... : .................................................................... 37

15.0 LIGHTING FOR SPECIFIC TASKS .............................................................................................................. 37 15.1

15.2 15.3

Molding of Metal and Plastic Parts: Discussion of Lighting and Equipment Choices .......... 38

15.1.3 Inspection of Sand Castings ................................................................................................. 38

15.1.1 Foundry Molding (Sand Casting) .......................................................................................... 38 15.1.2 Molding Parts of Die-Cast Aluminum and Injection Molded Plastic .................................... 38

15.1.4 Inspection of Die-Castings and Opaque Injection Molded Plastic Parts ............................. 39 Parts Manufacturing and Assembly ............................................................................................... 39 Machining Metal Parts ...................................................................................................................... 40


16.0 LIGHTING FOR SPECIFIC VISUAL TASKS .............................................................................................. 40

16.2 Flat Surfaces ...................................................................................................................................... 40 16.3 Scribed Marks .................................................................................................................................... 40

16.1 Convex Surfaces ............................................................................................................................... 40

16.4 Center-Punch Marks ......................................................................................................................... 41 16.5 Concave Specular Surfaces ........................................................................................................... 41 16.6 Flat Specular Surfaces ..................................................................................................................... 41 16.7 Convex Specular Surfaces ............................................................................................................. 41 16.8 Lighting and Visibility for Specific Sheet Metal Fabrication ...................................................... 42

16.8.1 Punch Press ......................................................................................................................... 42 16.8.2 Shear ..................................................................................................................................... 42

16.9 Lighting for Large Component Sub- and Final Assembly .......................................................... 42 16.10 Control Rooms ................................................................................................................................. 43 16.11 Warehouse and Storage Area Lighting .......................................................................................... 44

16.1 1 . 1 Types of Warehouse Area and Storage Systems ............................................................... 44 16.1 1.2 Warehouse Illuminance ...................................................................................................... 44 16.1 1.3 Warehouse Lighting Design Considerations ...................................................................... 45

17.0 OUTDOOR AREA LIGHTING ....................................................................................................................... 46 17.1 Projected Lighting Systems ........................................................................................................... 46 17.2 Distributed Lighting Systems ......................................................................................................... 46 17.3 Outdoor Tower Platforms, Stairways and Ladders ...................................................................... 46 17.4 Special Equipment ............................................................................................................................ 47 17.5 Low Illuminance and Visual Acuity Outdoors .............................................................................. 47

References .............................................................................................................................................................. 47

Annex A l The Basis for Deviating from Recommended Illuminances .................................................................. 48

Annex A2 Recommended Illuminance Values (target maintained) for Industrial Lighting Design ................... 51

Annex B Predictive Methods for Determining Visual Comfort Probability (VCP) and Unified Glare Rating (UGR) ................................................................................................................ 64

Annex C Average Illuminance Calculation: The Lumen Method ......................................................................... 69


FOREWORD (This Foreword is not part of the American National Standard and Practice ANSIAESNA RP-7-01.)

While the objectives of this Recommended Practice are to give a comprehensive treatment of lighting in the industrial environment, there are many spaces in a modern industrial complex that are used for purposes other than manufacturing. These include off ices, meeting, conference and reference spaces. It is suggested that the reader refer to the most recent version of these other IESNA Recommended Practices and Design Guides for the appropriate lighting recommendations for spaces not covered in this publication:

ANSMESNA RP-1, Recommended Practice on Office Lighting IESNA RP-5, Recommended Practice of Daylighting IESNA RP-20, Recommended Practice on Lighting for Parking Facilities ANSI/NECA/IESNA 502, Recornmended Practice for Installing Industrial Lighting Systems IESNA DG-2, Design Guide for Warehouse Lighting

warm-up periods or stroboscopic effects created where rotating paris are present. The ability of the lamps to render colors accurately may have an effect on the recognition of colors or product components and safety colors used to protect the workers from dangerous conditions within the work place. Many industrial operations take place in hostile environments, and the hardware used in these locations must be designed and manufactured to survive these conditions. For these reasons, and many others, great care is required to provide an effective, efficient and readily maintainable lighting system to help modern industrial workers produce at the peak of their ability in a safe environment.

2.0 LIGHTING THE INDUSTRIAL ENVIRONMENT

Providing a successful lighting design for a modern industrial facility is a complex task. In the last three decades of the 20th century, much has been leamed about lighting and its positive effects on the well being of people. The goal of providing an efficient, reliable and easily maintainable lighting system, making use of all of the knowledge available to the designer today, is a task that requires experience and considerable planning.

1 .O INTRODUCTION 2.1 General Design Considerations for Lighting

Industrial Areas A well-designed lighting system can make an important contribution to the success of an industrial facility. Unfortunately, too often the lighting is treated as an afterthought during the planning and construction of these facilities. Great attention is paid to the physical dimensions of the building, to the flow of the process and materials, and to production equipment.

It is common that only horizontal illuminance is considered in providing an environment in which to perform industrial tasks. However, many industrial tasks do not occur in a horizontal plane. There are many features of the lighting system, other than quantity of light, which make a significant contribution to the efficiency of the industrial worker. Placement of the luminaries is critical to providing light of the proper quality, as well as quantity and direction, to allow fast, easy recognition of operations, which may be taking place at high speeds in portions of production machinery where ambient light cannot easily penetrate. Selection of the luminaire distribution can be important to rendering the visual task properly when that task is multi-dimensional rather than flat, and when the task occurs in a plane other than horizontal. The operation of the light sources must be understood to ensure that the proper lamps are selected. Improper light source choice can result in difficult and potentially dangerous conditions caused by long

The designer of an industrial lighting system should carefully consider all of the following design criteria since any single issue, or combination of several, could be important in planning a successful industrial lighting installation. (These criteria are not necessarily arranged in order of importance since priorities will vary for different industries or different locations within an industrial complex.)

1. Determine the quality of illumination for the manufacturing processes involved. (See the Industrial Lighting Design Guide in Figure 1 (a) and Section 3.0.)

2. Determine the quantity of illumination for the manufacturing processes involved. (See the Industrial Lighting Design Guide in Figure 1 (a) and (b), Section 4.0 and Annex C.)

3. Determine the lighting required for safety and ensure all three conditions (quality, quantity and safety) are properly weighed and addressed in the final design.

4. Select listed or approved lighting equipment that will provide the requirements of quality and quantity, including photometric characteristics, as well as the mechanical performance required to meet installation and operating conditions.

5. Arrange equipment so that it will be safe, easy and


A B C

practical to maintain. Evaluate Figure l(b) Determination of Illuminance Categories.

Public Spaces Simple orientation for short visits Working spaces where simple visual tasks are performed

30 lx (3 fc) 50 lx (5 fc) 100 lx (10 fc)

operating conditions that may create dangerous or unacceptable risks to people, plant or equipment.

6. Consider the energy, economic and operating characteristics of the selected lighting system and be sure all factors have been properly weighed and balanced against the five considerations above before finally accepting the design.

2.2 The IESNA Lighting Design Guide and Industrial Lighting Design Recommen- dations

In the past, the IESNA has always recommended illuminances for specific applications or visual tasks. Such recommendations were often mistak- en as the primary or even sole criterion for lighting design. Beginning with the publication of the IESNA Lighting Handbook, 9th Edition,’ the Society has introduced a new, formal system for considering a wide range of lighting design criteria important for a high- quality visual environment. This new system emphasizes quality factors as

D

E

F

Performance of visual tasks of high contrast and large size Performance of visual tasks of high contrast and small size, or visual tasks of low contrast and large size Performance of visual tasks of low contrast and small size

300 ix (30 fc)

500 lx (50 fc)

1 O00 lx (1 OOfc)

well as illuminance. reflections, measured illuminance should be within * 10 percent of the recommended value. It should be noted, however, that the final illuminance may deviate from these recommended values due to other lighting design criteria. Central to the new system is the

G

IESNA Lighting Design Guide. The columns of the Design Guide list multiple criteria important for a high quality visual environment, while the rows list specific locations and tasks alphabetically. At each row/column intersection, a shaded block indicates the level of importance for each criterion as it relates to the associated location or task: very important = solid shading; important = medium shading; somewhat important = light shading; and not important or not applicable = no shading (blank). Those portions of the Design Guide that apply to industrial applications are presented in Figure 1 (a), (page 9.) (See Chapter 1 O in the IESNA Lighting Handbook, 9th Edition, for the complete Guide for all other applications.)

Performance of visual tasks near threshold 3000-10,000 IX (300- 1 O00 fc)

3.0 QUALITY OF LIGHTING IN INDUSTRIAL FACILITIES

A pleasant and comfortable environment is desirable and will generally result in a happier and more productive worker. There are various factors to consider in determining the quality of the visual environment. They appear in the column headers in the Design

2

Guide in Figure 1 (a). These include luminances of room surfaces, modeling of objects, glare, shadows, source/task/eye geometry, flicker and strobe, color appearance and color contrast, and daylight integration and control.

3.1 Luminance and Luminance Ratios

The ability to see detail is strongly influenced by the contrast between the task detail and its background. The greater the contrast, or difference in luminance, the more readily the task is seen. However, the eyes function more comfortably and efficiently when the luminances within the total visual environment are fairly uniform. Therefore, all luminances in the field of view should be carefully controlled. In manufacturing, there are many areas where it is not practical to achieve the desirable luminance relationships as those more easily achieved in areas such as offices. But between the extremes of heavy manufacturing and office spaces lie the bulk of industrial areas. Therefore, Figure 2 (see page 6 has been developed as a practical guide to recommended maximum luminance ratios for industrial areas.


Figure l(a). Lighting Design Guide for Industrial Diications.

3




Figure 2. Recommended Maximum Luminance Ratios.

Environmental Classification” A B

3 to 1 3 to 1 1 to3 1 to3 10 to 1 20 to 1 1 to10 1 to20 20 to 1

1. Between tasks and adjacent darker surroundings

3. Between tasks and more remote darker surfaces 4. Between tasks and more remote lighter surfaces 5. Between luminaries (or windows, skylights, etc.)

6. Anywhere within normal field of view 40 to1 +

2. Between tasks and adjacent lighter surroundings

+ and surfaces adjacent to them

C 5 to 1 1 to 5

+ + +

+ I

* Classifications are: A- Interior areas where reflectances of space can be controlled in line with recommendations for optimum visual conditions. B- Areas where reflectances of immediate work area can be controlled, but control of remote surround is limited. C- Areas (indoor and outdoor) where it is completely impractical to control reflectances and difficult to alter environmental conditions. + Luminance ratio control not practical

Workers may experience eye adaptation changes in shifting their gaze away from a task if the new principal luminances in a changed viewing direction are significantly different from those in the task surround. This is sometimes called transient adaptation. In certain industrial operations, workers may experience “transient adaptations” continuously during a normal workday. Problems caused by luminance differences in the environment can be reduced or avoided by providing the recommended luminance ratios.

To achieve the recommended luminance relationships, it is necessary to carefully select the reflectance values of all room surface and equipment finishes, as well as control the candela distribution of the lighting equipment. Figure 3 lists the recommended reflectance values for industrial interiors and equipment. High reflectance surfaces are generally desirable to provide the recommended luminance relationships and maximize the utilization of light. They also improve the appearance of the workspace. A large industrial room with dark surfaces can elicit a “cave-like” sensation. At the same time, there may be visibility consequences from improper luminance ratios for tasks located adjacent to dark walls or where the wall forms a significant part of the task background. If low-reflectance walls and ceilings exist, a major improvement in lighting system performance can be achieved by refinishing those surfaces to the reflectances recommended in Figure 3.

In many industries, machines are painted to present a completely harmonious color environment. A slightly darker background than the task detail is usually preferred. Stationary and moving parts of machines should be finished with contrasting colors standardized within the facility to reduce accident hazard.

When color combinations are selected for the building and machinery parts, the color rendering charac-

Surfaces Reflectance (%y Ceiling 50% - 70% Walls 40% - 60% Desk & Bench Tops, Machines

Floors 20% & Equipment 25% - 45%

- ‘Reflectance should be maintained as near as practical to recommended values

Figure 3. Recommended Reflectance Values (Applying to Environmental Classifications A and 6 in Figure 2)

teristics of the lamps being used in the space must also be considered. Failure to do this could produce a color appearance completely different from the one anticipated. Paint samples should always be reviewed under samples of the actual lamps to be installed to avoid annoying surprises after the project is completed.

3.2 Modeling of Objects

Lighting will reveal the depth, shape and texture of an object. In industrial applications, modeling of the visual task can be critical to assessing quality of raw materials, quality of finished goods and degree of consistency in manufacturing processes. Appropriate direction and distribution of light may vary depending on material and task. Diffuse ambient lighting is often inadequate for assessing fine texture; task lighting may be used to provide the required direction, distribution and intensity of light. (See Section 12.0, Supplementary Task Lighting.)

3.3 Glare and Visual Comfort

Glare is the sensation produced by luminance within the visual field that is sufficiently greater than that to

6


Angle of

which the eyes are adapted. Glare may cause annoyance, discomfort or loss of visual performance and visibility. Direct glare results from high luminances or from unshielded light sources. Glare can be reduced by decreasing the luminance or area of the glare source, by raising the glare sources further above the line of sight, and by boosting the ambient illuminance.

Angle of Source

Reflected glare results from high luminance sources or from luminous difference reflected from specular (shiny) surfaces. ?Veiling reflections? are contrast- reducing reflections from semi-specular surfaces that may reduce task visibility.

Disability glare is caused by a veiling luminance superimposed. on the retinal image within the eye, which reduces visual performance or visibility, and is often accompanied by discomfort. Reducing illuminance at workers? eyes and/or raising the source of the disability glare can alleviate the problem.

Discomfort glare produces visual discomfort without necessarily interfering with visual performance or visibility. It occurs when luminous objects (or reflections of luminous objects) have significantly higher luminance than the balance of the person?s field of view. Size, luminance and angular displacement from the line of sight are all factors. Even a source that is directly overhead, if bright enough, can cause discomfort glare.

Individual tolerances vary, but visual evaluations of discomfort glare have resulted in numerical systems of rating the discomfort glare, based on luminaire luminance, luminaire size, luminaire positions, room dimensions, surface reflectances and average illuminance.

There are two methods used for predicting glare; an empirical prediction system used in North America called the Visual Comfort Probability (VCP) system, and a Unified Glare Rating System (UGR) used primarily in Europe. See Annex B for a discussion of each. Note that VCP is used for direct distribution fluorescent luminaries only.

The glare sensation from an industrial system can be reduced by decreasing the luminance of the light sources or the luminance of the luminaries; for example, choosing a luminaire with a larger refractor. So- called ?high-bay? high intensity discharge (HID) systems, where luminaries are mounted 7.6 m (25 ft) or more above the floor, are considered satisfactory with respect to glare. High-bay luminaries, however, often provide a variety of socket positions, which may place lamps so low in the reflector that they have little or no cutoff. For such situations, luminaire accessories, such as louvers, may be considered.

Specific glare ratings for lighting in actual rooms may be calculated using the methods described in Annex B.

Reflected glare can be minimized or eliminated by using light sources of low luminance or by orienting the work so that reflections are directed away from the normal sight line to the task. It is often desirable to use large-area luminaries of low luminance located over the work. See Section 12.0, Supplementary Task Lighting for possible solutions to such problems.

Unshaded factory windows frequently contribute to glare sensations among production personnel attrib- utable to a direct view of the sun, bright portions of the sky or even light surfaces of adjacent buildings. Direct sunlight entering the work area may cause glare when reflected off interior surfaces.

.

3.4 Material Characteristics

Lighting designers must pay attention to material characteristics of visual tasks, such as texture, spec- ularity, transparency and translucency. These provide visual cues and are often a functional part of task contrast. They can also impact important process considerations such as degree of finish or completeness, material quality or correctness as well as other production issues. Modeling the principal tasks with a test installation will help determine the optimum lighting system and geometry. Such a test should include the actual task and a minimum of 4 luminaries at an appropriate mounting height and spacing.

Normal Figure 4 (a). Angle of incidence equals angle of reflection.

7


Bright images reflected from computer screens are frequently the cause of veiling reflections. (See Figure 4 (b).) Screen reflections may be caused by overhead luminaries, light colored clothing worn by employees, and unshielded windows or skylights. Means of control include total cutoff of light source images, changing VDT orientation and position, using better contrast screens, adding shields to the monitor, and blocking the view of luminous surfaces in the offending zone. (See Figure 4 (c).) For more detailed information on lighting for VDT workstations see latest version of IESNA RP- 1, Recommended Practice on Ofice Lighting.

Figure 4 (b). Veiling reflections in a VDT screen.

Figure 4 (c). Veiling reflections are minimized to enable the operator to clearly see the drawing on the screen. (Photo courtesy of Ruud Lighting.)

Veiling reflections also occur in manufacturing areas of an industrial facility. For example, in the electronics industry, solder used in the manufacture of printed circuit boards has specular characteristics. Glare reflected from the solder will hinder the ability of the worker to see the detail of the circuitry on the board.

Not all specular reflections on tasks reduce visibility. Incised markings on micrometers and other calibrating instruments are more easily seen when the angle of the light source creates a bright edge against a shadow to enhance the detail of the task. (See Section 16.1 .)

3.5 Shadows

Shadows can interfere with task visibility by placing detail in darkness (e.g., a body shadow on a machine task), or they can enhance definition of three-dimensional details (e.g., imperfections in tex- tiles). Point sources (e.g., incandescent or high intensity discharge lamps) create more defined shadows than fluorescent lamps, which produce diffuse shadows.

Generally, a large area of shadow, covering the whole task area, will simply lower the task illuminance. Shadows cast by the structure of the task may reveal detail, or may mask what needs to be seen. High reflectance surroundings help fill in and modify shadows, as do luminaries with 10 percent or more uplight when the ceiling cavity reflectance is over 50 percent. A combination of supplementary task lighting and general illumination is often the best approach, if care is taken to minimize glare.

The presence of shadows may be desirable, and the interplay of highlight and shadow helps to define the form of many visual tasks. Lighting vertical surfaces to at least half the horizontal illuminance level often brings the ratio of highlight to shadow into a tolera- ble range for three-dimensional tasks. Some shadow will still be present, which helps to model the task and reveal form. Since each visual task has an optimum range of modeling, a careful evaluation of critical visual tasks should be made to determine the effects of various ratios of horizontal vs. vertical illuminance on visibility.

Obstructions below the luminaire mounting plane, such as pipes and ducts, and the location and orientation of the task, affect the availability of vertical illuminance. Obstructions can also produce shadows, as can an operator positioned between the task and the luminaries. When a task is close to a wall, and the operator is facing the wall, relatively few luminaries are likely to contribute to task illuminance. In these cases, high wall reflectances (greater than 60 percent) can improve task visibility.

3.6 SourceKasiúEye Geometry

The angular relationships between the viewer, the task and the luminaire are frequently critical to task visibility. Industrial tasks are often three-dimensional, and they often move. Because viewing angles are dynamic, the source/task/eye geometric relationships must be understood for individual work areas. The geometry can enhance contrast (e.g., scribed marks on a micrometer) or reduce it (e.g., viewing a meter dial through glass).

8


Lamp Type Mercury 250W Warm Deluxe 250W Cool Deluxe 250W Deluxe White 250W Deluxe White

3.7 Task Visibility - Flicker and Strobe

Ballast Flicker Index

Reactor O. 127 Reactor 0.137 Reactor 0.131

CWA íM-H tvDe) O. 172

Flicker is the rapid variation in light source intensity, usually most noticeable in peripheral vision. The output of lighting systems that operate on alternating current power varies in output at a rate that is twice the cyclic frequency of the input power. Sometimes this “strobe effect” appears to slow or even stop the movement of objects. This can be annoying or dangerous for operators of rotating or other rapidly cycling equipment.

1 OOW Deluxe White 400W Deluxe White 400W Deluxe White

The “flicker index” has been established as a reliable relative measure of the cyclic variation in output of various light sources at a given power frequency and takes into account the waveform of the light output as well as its amplitude. The flicker index assumes values from O to 1.0 with zero for steady light output. Higher values indicate increased possibility of noticeable stroboscopic effect as well as lamp flicker.

cw O. 183 Reactor 0.121

CWA (M-H type) 0.144

Most fluorescent lamps have low flicker indices, and typically do not cause problems when operating on a 60-Hz power supply. Their visible flicker is virtually elim-

250W Deluxe

inated when operated at high frequency on electronic ballasts. Sensitivity to flicker varies among individuals, vanes across the visual field and often will be unno- ticed. Designers are cautioned to consult with a lamp manufacturer about the flicker index of a particular fluorescent lamphallast combination before it is used in an area where flicker or strobe could be a problem.

Reactor or CWA 1 0.131

The flicker in HID lamps depends on the lamp type and the ballast circuit. Figure 5 illustrates the variation in flicker index for mercury (used infrequently today), metal halide and high pressure sodium lamps for several ballast types operated at 60-Hz. The flicker index is considerably higher in 50-Hz power systems. Using electronic ballasts having high-frequency or rectangular wave characteristics can be effective in reducing the flicker effect. Operating fluorescent or HID lamps on alternate phases of a three- phase power supply will reduce observed flicker when the light from luminaries connected to all three phases is well mixed before it reaches the workplane. This is accomplished by using luminaries with a wider spacing criterion, designing for 50 percent light pat-

Metal halide 250W High Color Quality

175W Coated 250W High Color Quality

Figure 5. Flicker Index for HID Lamps Operated on Different Ballast Types.

Reactor 0.080 HPS-CWA 0.102

CWA 0.083

175 W Clear-Horizontal 175W (3200K) 250W Coated (A) 250W Clear-Vertical 250W Clear-Horizontal 250W Coated (B)

I 1OOW Deluxe White

CWA 0.092 CWA 0.090 CWA 0.070 CWA 0.102 CWA 0.121 CWA 0.092

I C W-Prem ¡um I 0.142 I

250W Clear-Vertical 250W Clear-Horizontal 400W Clear-Vertical 400W Clear-Horizontal 1 OOOW Clear (vert.)

C WA-Premium 0.088 CWA-Premium 0.097

CWA 0.086 CWA 0.095 CWA 0.067

I 250W Standard I Reactor or CWA I 0.200 I

I 175 W Clear-Vertical I CWA I 0.078 I

9


tern overlap, and powering adjacent luminaries from alternate phases.

3.8 Color Rendering

The selection of a lamp color for an industrial facility requires consideration of at least two factors, color appearance and the color rendering ability of the source. The color appearance is important to create a pleasant and attractive atmosphere in which to work and a space that will promote high productivity.

Color rendering is the general expression for the effect of a light source on the color appearance of an object compared to the color appearance under a reference light source. Daylight and incandescent light sources are generally thought of as having “good color rendering properties because objects look the way we expect them to look under those sources. Fluorescent and HID lamps may have a wide range of color rendering properties depending on the composition of the arc tube gases and the materials coating the inside of the lamp envelope.

3.8.1 Color Rendering Index, (CRI)

The Color Rendering Index (CRI) is a system recommended by the International Commission on Illumination (Commission Internationale de I’Eclairage (CIE)) for measuring and specifying the ability of a light source to render colors. The system rates a lamp’s CRI in terms that represent the degree of color shift of an object under a test lamp in comparison with its color under a standard lamp of the same correlated color temperature. Note that CRI is only useful when com- paring two or more lamps of the same correlated color temperature. Lamp CRIS used where color rendering is unimportant may be as low as 20. When color rendering is important, the CRI should exceed 70. Where color rendering is critical, the CRI should exceed 85.

The color rendering index of the lamps selected for the lighting system design should permit the workers to efficiently and safely perform their tasks. Many industrial operations now require color discrimination during the manufacturing process. Instances have arisen where an HID source with a relatively low color rendering index has been used in a space where color coding was employed in production control and scheduling. The colors of the codes were not readily identifiable under the low color rendering HID source. The solution was to provide supplementary lighting with fluorescent lamps having a higher color rendering index, permitting the workers to direct the operations with the necessary speed and efficiency. Color discrimination can be necessary during assembly and “parts picking.” For example, in the lighting industry, the parts selection task might involve discerning between gold, champagne

gold, straw and wheat downlight reflectors or selecting among various screw or wire insulation colors.

The need for high color rendering sources varies widely throughout industrial facilities. In warehouse areas, the task may be reading black printing against the color of a cardboard package. In this example, a lamp with the very low color rendering index may not only suffice, but also actually enhance the visibility of the printing by increasing the contrast of the visual task. On the other hand, where color comparison or color discrimination is critical, it will be necessary to select a source with a high color rendering index to provide the color quality necessary to perform those visual tasks.

3.8.2 Safety Colors

Safety colors are used to indicate the presence of a safety hazard, such as an open pit or a lift truck traffic lane, or a safety facility, such as a first aid station. These are carefully developed colors, which are specified in American National Standard 2535.1 -1 998, Safety Color Code. The background around these colors should be kept as free of competing colors as possible, and the number of other colors in the area should be kept to a minimum. Illumination in the area of safety color markings should permit positive identification of the color, hazard or situation without distortion or obscuration of the message to be conveyed.

The specification of these colors is given in Figure 6. Designers must be aware that these specifications have been developed based on CIE standard illuminant “ C (a laboratory simulation of the spectral power distribution of average daylight). Therefore, the colors will be recognizable under daylight, conventional incandescent and fluorescent sources, which have a broad spectrum. Note that high intensity discharge sources render some colors differently than these other source types. This may cause some confusion in recognition of safety colors at illuminances of 5 lux (0.5 fc) and lower.

3.9 Daylight Integration and Control

A view of the outdoors is believed to be important for human psychological and physiological reasons. While daylight can be used to help light a space, extra care should be taken in industrial environments to control the quantity and distribution of the light and its associated heat gain. It should be noted that more illuminance is sometimes needed on interior surfaces near windows to reduce the contrasts between those surfaces and the windows. Daylighting is most effective for many interior spaces when used as ambient illuminance, but it is too variable to be considered a reliable source for task illuminance in industrial applications. (For information on the subject of daylighting see IESNA RP-5-99, Recommended Practice of Daylighting. )

10


Figure 6. Specification of ANSI Safety Colors Viewed under CIE Standard Illuminant C.

Color Name Munsell Notation CIE Specification ISCC-NBS Name v V V 1 A

0.3269 12.00 Vivid Red Safety Red 7.5R 4.0114 0.5959 Safety Orange 5.OYR 6.0115 0.5510 0.4214 30.05 Vivid Orange Highway Brown 5.OR 2.7515 0.4766 0.3816 5.52 Moderate Brown

0.4562 0.4788 59.10 Vivid Yellow Safety Yellow 5.0Y 8.0112 Strong Green

O. 1690 0.1744 9.00 Strong Blue Safety Blue 2.5PB 3.5110 Safety Purple 1O.OP 4.5110 0.3307 0.2245 15.57 Strong Reddish Purple Safety White N9.01 0.3101 0.3 162 78.70 White Safety Gray N5.01 Safety Black N1.51 0.3101 0.3 162 2.02 Black

Safety Green 7.5G 4.019 0.21 10 0.4 120 12.00

0.3101 0.3 162 19.80 Medium Gray

4.0 QUANTITY OF LIGHTING IN INDUSTRIAL FACILITIES

The recommended illuminances provided in the Lighting Design Guide (Figure 1 (a)) are based on the Society’s consensus judgement of best practice for ‘Yypical” applications. Typical conditions, however, may not be appropriate for a specific application. As a professional, the lighting designer should have a better understanding of the particular space and the needs of occupantdclients than that which can be represented by a recommended illuminance value for a typical space. The lighting needs and requirements of an individual industrial facility will depend on many factors. Certain facilities may include multiple lighting needs within the same production area, resulting in the deliberate use of non-uniform lighting.

Beginning in 1979, the IESNA established nine illuminance categories (A through i), and these were used in previous editions of this recommended practice. Each category had general descriptions of the visual task, irrespective of the application. This system has now been modified in the following significant ways:

The recommended illuminances on industrial task planes are now provided with reference to a specific application. The tasks may be horizontal, inclined or vertical.

The nine original illuminance selection categories have been reduced to seven categories and orga- nized into three sets of visual tasks [orientation and simple (A, B, C), common (DI E, F) and special (G)]. The seven new letter categories are presented and described in Figure 1 (b). They also appear in the “Illuminance” columns of Figure 1 (a).

Guided by scientific literature and practical experience, IESNA’s recommended illuminance values now increase roughly logarithmically with increasing task difficulty.

Occasionally the visual task in a specific space is not typical. The information in Annex Al should be used to adjust the illuminance for that task. In addition, illuminance recommendations for tasks/ spaces/industries not covered in Figure 1 (a) are contained in Annex A2.

4.1 Illuminance: Horizontal, Vertical and Inter- mediate Planes

For the first part of the 20th Century, when “lighting levels” were discussed, it was usually understood that the reference was to illuminance on the horizontal surface. As more has been learned, it is now known that a horizontal plane is not the only plane that is important, particularly in an industrial facility. For that reason, note that when determining illuminance, the orientation of the task (horizontal, vettical or intermediate inclined plane) should be known.

4.1.1 Horizontal Illuminance

Horizontal illuminance is important and should not be ignored. This is the light that allows us to predict how clearly tasks and items will be seen when they are on a flat work surface, shelf or on the floor. Horizontal illuminance is important for task visibility, material handling and general circulation. Uniform horizontal illuminance (where the maximum level is not more than one-sixth above the average level, and the minimum, not more than one-sixth below) is frequently appropriate for specific industrial interiors where tasks are closely spaced and where there are similar tasks requiring the same amount of light. In such instances, uniformity permits flexibility of functions and equipment locations. Neighboring areas with extreme luminance differences are undesirable because continuously adapting between two significantly different luminance levels physically adjacent to each other can be visually fatiguing to the worker. Uniformity may be more important in industrial lighting than in some other applications. While non-uniform lighting can add interest in applications that are of a more aesthetic

11


nature, industrial spaces can benefit from high-quality uniform lighting when the location of the task cannot always be accurately predicted. Uniform lighting also allows repositioning of task locations or production machinery without needing to relocate luminaries. This can be particularly beneficial in high-bay industrial facilities where the cost and inconvenience of moving luminaries located 9 m (30 feet) or more above the production floor can be substantial.

There are instances where non-uniform lighting is appropriate. Maintaining uniformity between adjacent areas, which have significantly different visibility (and illuminance) requirements, may be wasteful of energy - for example, a storage area adjacent to a machine shop. In such instances, different lighting levels are required, according to the needs of the space. This may be accomplished by using similar luminaries with different lamp wattages or distributions, different numbers of lamps per luminaire or by adjusting the number of luminaries per unit area, making sure the other requirements of the lighting design are met.

4.1.2 Vertical Illuminance.

In an industrial setting, vertical illuminance, and the illuminance at other planes between horizontal and vertical, is very important. In many large-parts assembly areas, work takes place on the underside of a major component, such as the wing or fuselage of an aircraft. Work performed deep within the recesses of production equipment such as presses, breaks or molding machines requires that the light penetrate into the machine to the location of the task for efficiency and safety. This may be accomplished by using wide-distribution general lighting equipment (with a majority of the light output 40” to 70” from the vertical). Light is reflected at high angles and high reflectance surfaces are provided in the work area. The use of supplementary lighting also helps to put the light directly on the task.

Diffuse light, including up-light components, from luminaries with very wide distribution (such as “low bay” HID luminaries) can have additional benefits in an industrial environment. The wide distribution can mitigate the effects of lamp outages in a single luminaire and may allow production to continue in a normal manner without having to spot-replace lamps as they fail. Wide-distribution luminaries also tend to produce a higher level of vertical illuminance (and wall luminance), at some sacrifice in horizontal illuminance. This can be a definite advantage where the seeing task is in a plane other than horizontal and there is a need to increase the vertical component of the lighting for task visibility. Care must be exercised, however, to ensure that the wider light distribution does not produce discomfort or disability glare beyond workers’ tolerances.

Industrial tasks come in all shapes and sizes. Flat tasks may be viewed in a horizontal plane or in planes at any number of other angles. The visual task associated with solid parts can be made more visible by a number of means including supplemental lighting and shadowing to emphasize the shape of the object. Harsh shadows should be avoided, but some shadow effect may be desirable to accentuate the depth and form of objects. There are a few specific visual tasks where clearly defined shadows improve visibility, and such effects should be provided by supplementary lighting equipment arranged for the particular task. Refer to the material in Section 12.0, Supplementary Lighting for more information.

Industrial lighting design requires a great deal of information about the tasks to be performed in the space. Because of this, the lighting designer should carefully discuss the manufacturing process with the facility personnel to obtain sufficient background information for proper evaluation of all of the design requirements. Personal visits to similar operations can be invaluable and are recommended whenever practical. Interviews with workers can also reveal information that might otherwise not be seen directly.

4.2 Initial and Maintained Illuminance

The quantity of light (illuminance) required depends primarily upon the seeing task, the time to perform the task, the worker, and the importance of the various task parameters in performing the work.

The illuminance will determine the worker’s adaptation to the visual environment. In today’s industrial facilities, there may be hazards, such as cranes, fork-lift trucks, conveyors and rotating machinery, which can affect the illuminance requirements. In locations where dirt accu- mulates rapidly and adheres readily to luminaire and room surfaces, and where maintenance is inadequate to keep lighting systems operating at design levels, the “light loss factor” used in calculating the required illuminance must be reduced, thereby increasing the initial illuminance, to compensate for the poor maintenance. This practice is not necessarily energy efficient, but may be justified to assure the worker has adequate light to safely and efficiently perform the required visual tasks. Other measures are available to compensate for the loss of light normally experienced through the life of a lighting system. Automatic control systems can offset the degradation of the lighting system due to age. Automatic switching systems can turn lights off when they are not needed, or switch them into a power-saving mode, provided that occupancy sensors are used for returning the lights to operating levels.

The number of luminaries required to meet the recommended illuminance can be calculated using a

12


basic manual procedure (such as the Lumen Method in Annex C ) or any of a number of commercially available computer based calculation programs to calculate the number of luminaries required. It is important that the lamp and luminaire characteristics, light loss factors and room characteristics discussed later be carefully selected to assure the acceptability of the installed lighting system. Many computer based lighting calculation programs now allow partitions and equipment to be included in the input data resulting in a more realistic modeling of the space.

4.3 Lighting System Maintenance

Industrial facilities often present challenging maintenance problems. Luminaries may be located far above the floor over large production equipment. Plant operations often will not tolerate interruptions for lamp and luminaire maintenance. Where cranes are present in high bay areas, they can often be used as the maintenance platform. This may be possible during normal production times but, more often, maintenance will have to be performed during non-production times. Platforms may be used to service lighting equipment or disconnecting hangers installed to permit the luminaire to be disconnected by chain or cable from the floor or some intermediate level and lowered to permit servicing from that level. Where the layout of the space will permit, telescoping platforms can provide the necessary access to luminaries.

Good maintenance programs can be effective in reducing the total power of an installed lighting system. A shorter relamping and cleaning cycle can reduce the number, or wattage, of the luminaries and, thereby, reduce the electrical load of the lighting system. Depending on the system, illuminance levels can depreciate to less than half of their initial level when lamps are replaced only as they fail, even if luminaries are thoroughly cleaned at relamping. Better light loss factors occur when systems are group relamped and cleaned at a shorter interval (typically 70 percent of rated life). The savings in labor usually offset higher lamp costs from a group maintenance program. A significant capital and operating (principally electric energy) cost saving is associated with programmed maintenance. Figure 7 shows the effect of cleaning and relamping on the output of a fluorescent lighting system and how these maintenance operations can have a beneficial effect on the system output.

It is critical to the proper operation of the lighting system that replacement lamps have not only the same electrical characteristics as the original lamps, but also the same envelope and color rendering characteristics. It is obvious that the lamp must fit in the luminaire’s socket and that the lamp’s electrical characteristics must permit operation on the system voltage

and with the luminaire’s auxiliary equipment. In addition, the envelope of the replacement lamps must match the original lamp design in shape and finish (coated or clear). Using the wrong lamp type can completely change the luminaire photornetrics and create entirely new lumen distribution patterns in the space. The lamp and ballast specifications from the American National Standards Institute (ANSI) and Canadian Standards Association (CSA) should be matched to assure proper lamp operation in both new and relamping situations.

Information on operating and maintaining the lighting system should always be documented for facility operating and maintenance personnel. As an example, lamp manufacturers direct that certain metal halide lamps may be used in open luminaries only if there is a schedule to cycle the lamps off at least once a week and to group relamp the area containing those lamps. These instructions are usually printed on the paper sleeve in which the lamp is shipped but that information may or may not be noted. For this reason, it is good practice to provide the owner’s, or occu- pant’s maintenance personnel with complete and clear written lighting system maintenance instructions at the time the project is completed.

Target illuminance levels are rarely achieved without some consideration during the initial design about the nature of on-site maintenance. This further demon- strates the need for providing a written maintenance program recommendation to assure the continued integrity of the design.

5.0 GENERAL LIGHTING EQUIPMENT

All lamp performance data such as life, lumen output and color are based upon statistical data. Lamp life, for instance, is the point in time when half of the lamps have failed and half are still operating. Lamp life is also dependent upon the number of hours per start (for example, 10 hrs/start vs. 120 hrdstart). It is important that the designer have a working knowledge of the underlying statistics in order to properly evaluate and/or compare systems and components..

5.1 Fluorescent Systems

5.1.1 Source Characteristics

Among the advantages of fluorescent lamps are their high luminous efficacy and relatively low brightness. That is, low brightness to the extent that open-reflector luminaries are often used in situations that have high wall and ceiling reflectances with low risk that workers will complain of excessive glare.

13


1 O0

90

80

70

c æ a 8 60 E

c

rn m C

al C rn v> al U

.- - -

.- c .- ; 50 ._

+ c o 40

2 a

c al

al

30

20

10

O

57 I I I I I I

-I-k-2-4-3.-4-I Clean Clean Clean Clean luminaires luminaires luminaires luminaires once and per 18 months; per 18 months; per 12 months; relamp 100% relamp 100% relamp 50% relamp 33-1/3% once per once per once per once per 36 months 18 months 18 months 12 months

= A-Temperature and voltage = D-Lamp lumen depreciation (LLD)

Í I B-Luminaire deterioration BI E-Lamp burnouts

F-Dirt accumulation on lamps and luminaires

C-Room surface dirt accumulation

- A

-B

-C

-D

-E

-F

)

O 3 6 9 12 15 18 21 24

Time in years

Figure 7. Effect of light loss factors on illuminance. Example uses 32-watt rapid-start lamps, operated 10 hours per day, 5 days per week, 2600 hours per year. All four maintenance systems are shown on the same graph for convenience. For a relative comparison of the four systems, each should begin at the same time and cover the same period of time.

A disadvantage is that the luminous flux generated is related to the surface area of the source; the greater the length, the higher the efficacy. In recent lamp designs, as the diameter of the lamp has been reduced, the lumens per unit area of the lamp surface area have increased.

The light output of fluorescent lamps decreases with accumulated operating time because of degradation of the phosphor coating and accumulation of light-absorbing deposits within the lamp. Protective coatings are sometimes used to reduce the phosphor degradation. Lamps with rare earth phosphors (T-5 or T-8) have better lumen maintenance than

lamps with halo phosphors.

Lamp life is determined by the rate of loss of the emis- sive coating on the electrodes or electrode failure. End of lamp life is reached when the coating is completely removed from one or both electrodes. The rated average life of fluorescent lamps usually is based on three hours of operation per start (3 hlstart).

Fluorescent systems offer the best color rendering ability over the widest ranges of apparent chromaticity (correlated color temperature (CCT) measured in Kelvin).

14


5.1.2 Fluorescent Luminaire Characteristics1 Performance

The most commonly used fluorescent general lighting luminaries for industrial applications are 8 feet long, multi-lamped with T-8 or in some older installations, the less efficient T-12 lamps. T-8, 800ma lamps operated on high frequency electronic ballasts may represent the best performance. Recent developments in performance of smaller diameter (T-5 and T-2) lamps offer suitable solutions for supplementary lighting. Most retrofits of industrial fluorescent luminaries use 4‘ T-8 lamps.

One benefit of fluorescent luminaries is that most two- lamp systems with electronic instant start ballasts (parallel lamp operation) offer redundancy; approximately half the light is still supplied if one lamp fails.

The luminous performance (efficacy or light output) and color of a fluorescent lamp result from the mercury vapor pressure within the lamp, which depends on temperature. The internal temperature of a luminaire can adversely affect the life of some types of fluorescent lamps. High ambient temperatures not only lower the lamp’s lumen output but also can change the electrical characteristics, bringing them outside the design range of the ballast. Long-term operation at higher currents shortens the life of the lamp.

The best fluorescent general lighting systems employ opaque sided reflectors for each lamp, with a 35- degree lamp cut-off along the luminaire transverse axis (across the luminaire), and louvers that provide similar cut off along the longitudinal axis (along the luminaire). Luminaries offen have apertures at the top that allow up-light and air movement. Air movement enables cleaner operation over an extended period of time in most open luminaries.

Fluorescent luminaries are generally considered for installation up to 6.0 m (20 ft) above the floor or platform level. However, with the proper combination of fluorescent lamps, ballasts and reflector design the use of fluorescent systems has been successfully expanded to mounting heights of 13.6 m (45 ff).

White finished diffuse reflector surfaces are the most common and are generally very efficient. Mirror finished optical surfaces vary widely in efficiency depending on the specific materials used and generally have lower apparent brightness when viewed from the side. Better optical control, available by using mirror finishes, may be desirable in narrow confining spaces or where obstructions block light from adjacent luminaries. The fluorescent source size may interfere with the optical designer’s attempt to direct source output at specific angles. This is often done to increase luminaire intensity at either nadir (for better

utilization in narrow or obstructed spaces) or at the spacing limit in order to obtain a wider spacing criterion. Other reflectors may be designed for wide or asymmetric distribution. It is important to use the lamp type specified since lamps and reflectors are designed to work in combination. As always, the improvement in visual comfort must be balanced with efficiency and maintenance concerns. If greater cutoff is required, select a deeper reflector.

Spacing criterion (SC) may be an unreliable gauge of how far apart general lighting luminaries can be spaced while still providing acceptable uniformity of horizontal illuminance. Typically, fluorescent industrial luminaries have spacing criteria of 1.3 to 1.6. (See Figure 8 page 16.)

5.2 High Intensity Discharge (HID) Lighting Systems

Because mercury vapor lamps have operating characteristics that are far inferior to both metal halide and high pressure sodium lamps for general lighting purposes, their use in modern industrial plants is rare. Therefore, this discussion of HID lamps for general lighting in industrial facilities does not include mercury vapor lamps. The reader should contact lamp manufacturers for mercury vapor lamp information.

5.2.1 Metal halide Lamps

Metal halide (MH) lamps are similar in construction to the earlier and simpler mercury vapor lamps. One of the major differences is the metal halide compounds included in the arc tube, which improve the color rendering qualities of metal halide lamps compared to those of even phosphor-coated mercury lamps. It is also possible, by adjusting the mix of the elements included in the arc tube, to vary the chromaticity of metal halide lamps. Metal halide lamps are available in wattages from 35 to 1000 watts. (There are 1500 watt lamps used primarily for sports lighting applications. ) The efficacy of MH lamps is greatly improved over mercury vapor with typical values of 75 to 125 lumens/watt (not including ballast losses). Metal halide lamps are made in both clear and coated outer bulb configurations and it is important that the correct lamp type be used in the luminaire to assure the lumen distribution for which the luminaire was designed.

Many metal halide lamps are life and lumen rated for operating in the vertical position. Using lamps designed for vertical operation in a horizontal operating position can seriously affect the lamp life and lumen output. For this reason, horizontal operating lamps have been specifically designed. These lamps will provide about 33 percent increase in life and approximately 25 percent increase in lumen output

15


Figure 8. Typical Fluorescent Luminaries.

0.97 0.97 0.97 0.84 0.81 0.79 0.73 0.68 0.64 0.64 0.58 0.53 0.56 0.50 0.45 0.50 0.43 0.38 0.45 0.38 0.33 0.41 0.34 0.29 0.37 0.30 0.26 0.34 0.28 0.23 0.31 0.25 0.21

Typical Intensity Distribution

0.92 0.92 0.92 0.89 0.89 0.89 0.81 0.79 0.76 0.78 0.76 0.74 0.70 0.66 0.63 0.67 0.64 0.61 0.61 0.56 0.52 0.59 0.55 0.51 0.54 0.48 0.44 0.52 0.47 0.43 0.48 0.42 0.38 0.47 0.41 0.37 0.43 0.37 0.33 0.42 0.37 0.32 0.39 0.33 0.29 0.38 0.33 0.29 0.36 0.30 0.26 0.35 0.29 0.25 0.33 0.27 0.23 0.32 0.27 0.23 0.31 0.25 0.21 0.30 0.24 0.21

DCC-1 1 80

O 1 2 3 4 5 6 7 8 9

10

50 I 30 1 10 10 70 I

1.03 1.03 1.03 0.93 0.88 0.83 0.83 0.75 0.68 0.75 0.65 0.57 0.69 0.57 0.49 0.63 0.51 0.42 0.58 0.45 0.37 0.53 0.41 0.33 0.50 0.37 0.29 0.46 0.34 0.26 0.43 0.31 0.24

pw-1 I 70 50 30

1.00 1.00 1.00 0.89 0.84 0.80 0.80 0.72 0.66 0.72 0.63 0.56 0.65 0.55 0.47 0.60 0.49 0.41 0.55 0.44 0.36 0.51 0.40 0.32 0.47 0.36 0.29 0.44 0.33 0.26 0.41 0.30 0.23

70 50 30 I 50 30 10 I 50 30 10 1 50 30 10 I Õ

0.92 0.78 0.67 0.58 0.51 0.46 0.41 0.37 0.34 0.31 0.29

Typical Luminaire

0.92 0.72 0.58 0.47 0.40 0.34 0.29 0.26 0.23 0.20 0.18

":" 1 EFF = 90.5%

0.86 0.86 0.86 0.73 0.70 0.68 0.62 0.58 0.55 0.54 0.49 0.45 0.48 0.42 0.38 0.43 0.37 0.32 0.38 0.32 0.28 0.35 0.29 0.25 0.32 0.26 0.22 0.29 0.24 0.19 0.27 0.21 0.18

Lamp = (2) F40T12 SC (along, across, 45') = 1.3. 1.5, 1.5 % DN = 78.2% % UP = 21.8%

0.80 0.80 0.80 0.67 0.65 0.63 0.58 0.55 0.52 0.50 0.46 0.43 0.44 0.40 0.36 0.40 0.35 0.31 0.36 0.31 0.27 0.33 0.27 0.24 0.30 0.25 0.21 0.27 0.22 0.19 0.25 0.20 0.17

0.77 0.61 0.49 0.40 0.34 0.29 0.25 0.22 0.19 0.17 0.15

O 1 2 3 4 5 8 7 8 9

10

0.87 0.87 0.87 0.81 0.78 0.76 0.75 0.70 0.66 0.69 0.63 0.58 0.64 0.56 0.51 0.59 0.51 0.45 0.55 0.46 0.40 0.51 0.42 0.36 0.47 0.38 0.32 0.44 0.35 0.29 0.41 0.32 0.27

0.82 0.82 0.68 0.66 0.58 0.54 0.49 0.45 0.43 0.39 0.37 0.33 0.33 0.29 0.30 0.26 0.27 0.23 0.24 0.20 0.22 0.18

~

0.71 0.58 0.47 0.40 0.33 0.29 0.25 0.22 0.19 0.17 0.16

0.98 0.98 0.98 0.89 0.85 0.81 0.80 0.74 0.68 0.73 0.64 0.58 0.66 0.57 0.50 0.61 0.51 0.43 0.56 0.45 0.38 0.52 0.41 0.34 0.48 0.37 0.30 0.45 0.34 0.27 0.42 0.31 0.25

% DN = 100%

0.74 0.74 0.74 0.64 0.62 0.61 0.56 0.53 0.50 0.49 0.45 0.42 0.44 0.39 0.36 0.39 0.35 0.31 0.35 0.31 0.27 0.32 0.28 0.24 0.29 0.25 0.21 0.27 0.23 0.19 0.25 0.21 0.17

E h ; Industrial, white enamel reflector, 20% up

0.77 0.67 0.60 0.70 0.59 0.51 0.64 0.53 0.45 0.59 0.47 0.39

0.51 0.39 0.31

EFF = 86.9% - 0.87 0.72 0.59 0.49 0.41 0.35 0.31 0.27 0.24 0.21 0.19 -

1.01 1.01 1.01 0.92 0.88 0.84 0.83 0.76 0.70 0.75 0.66 0.59 0.68 0.58 0.51 0.63 0.52 0.44 0.58 0.47 0.39 0.53 0.42 0.35 0.50 0.38 0.31 0.46 0.35 0.28 0.43 0.32 0.25

0.85 0.78 0.72 0.77 0.68 0.60 0.70 0.60 0.52 0.65 0.53 0.45 0.59 0.47 0.39 0.55 0.43 0.35 0.51 0.39 0.31 0.48 0.36 0.28

EFF = 89.3%

Industrial, white enamel reflector, down only

% DN = 86.4%

0.92 0.75 0.62 0.52 0.45 0.39 0.34 0.30 0.27 0.25 0.22 2-Lamp bare strip

Lamp = (3) F32T8 SC (along, across, 45') = 1.3, 1.6, 1.6 EFF = 72.7% % DN = 100 %UP=O

0.74 0.73 0.66 0.65 0.58 0.57 0.51 0.49 0.44 0.43 0.39 0.38 0.35 0.33 0.31 0.30 0.28 0.27 0.25 0.24 ! 0.23 0.22

0.81 0.81 0.81 0.74 0.72 0.70 0.66 0.63 0.61 0.60 0.56 0.52 0.54 0.49 0.46 0.48 0.44 0.40 0.44 0.39 0.35 0.40 0.35 0.31 ' 0.37 0.32 0.28 0.34 0.29 0.25 0.31 0.26 0.23

0.77 0.77 0.71 0.69 0.64 0.61 0.58 0.54 0.52 0.48 0.47 0.43 0.43 0.38 0.39 0.35 0.36 0.31 0.33 0.29 0.31 0.26

0.77 0.68 0.59 0.52 0.45 0.40 0.35 0.31 0.28 0.25 0.23

0.74 0.74 0.68 0.67 0.62 0.60 0.56 0.53 0.51 0.47 0.46 0.42 0.42 0.38 0.38 0.34 0.35 0.31 0.32 0.28 0.30 0.26

0.85 0.85 0.85 0.79 0.77 0.74 0.73 0.69 0.65 0.68 0.62 0.57 0.62 0.55 0.50 0.58 0.50 0.44 0.53 0.45 0.40 0.50 0.41 0.36 0.46 0.38 0.32 0.43 0.35 0.29 0.40 0.32 0.27

2 x 4, 3-Lamp parabolic troffer with 3 semi-spec. louvers, 18 cells

Lamp = (3) F40T12 SC (along, across, 45') = 1.3, 1.6, 1.5 %DN=100 %UP=O EFF = 66.2%

0.63 0.58 0.53 0.59 0.52 0.47 0.54 0.47 0.42 0.50 0.43 0.37 0.47 0.39 0.33 0.44 0.35 0.30 0.41 0.33 0.27

- 0.70 0.65 0.59 0.53 0.48 0.44 0.40 0.36 0.33 0.31 0.28 -

- 0.70 0.64 0.57 0.50 0.45 0.40 0.36 0.32 0.29 0.27 0.24 -

- 0.74 0.66 0.58 0.51 0.46 0.41 0.36 0.33 0.30 0.27 0.25 -

- 0.74 0.64 0.56 0.48 0.42 0.37 0.33 0.30 0.26 0.24 0.22 -

0.77 0.72 0.67 0.62 0.57 0.53 0.49 0.46 0.43 0.40 0.37 -

0.77 0.70 0.63 0.57 0.51 0.46 0.42 0.38 0.35 0.32 0.30 -

2 X 4, 3-Lamp parabolic troffer with 4" semi-spec. louvers, 18 cells

16


over universal burning position lamps when operated in the horizontal position. A special base and socket are required for all of the horizontal burn, high-output, MH lamps to assure the arc tube is properly positioned. These lamps should always be used in luminaries equipped with the proper socket.

Because MH arc tubes produce high-energy ultraviolet radiation, some lamps are manufactured with an electrical cutout that will automatically extinguish the lamp if the outer envelope should crack or rupture in a manner that would normally still allow the arc to operate. These lamps should be used in locations where it is necessary to limit UV radiation and where the luminaire will not provide the necessary protection.

Transparent sleeves (shrouds) may be used internal- ly in some single ended (screw-base) MH lamps for two reasons. Thin walled shields are used to help achieve a more uniform arc tube temperature, which will improve the lamp performance. Heavy walled shrouds are used on lamps designed for use in open luminaries. The heavy walled shroud is designed to contain the hot quartz particles and protect the outer bulb of the lamp from breaking in the event the arc tube should fail.

5.2.1.1 Pulse-start and Ceramic Metal halide Lamps

The choice between metal halide (MH) and high pressure sodium (HPS) high intensity discharge (HID) lamps was, until recently, a choice between the superior color of MH (although some MH lamps display strong color shift near end-of-life) versus the improved lumen output and longer life of HPS. HPS was frequently the choice. Recently, however, the advent of pulse-start (high wattage 175W - lOOOW, and low wattage 35/39W - 150W) and ceramic metal halide lamps has blurred the line between these choices.

The pulse start lamps have improved starting .times, some starting as much as three times faster than conventional MH lamps. They also start more reliably, have better lumen maintenance, improved lamp life, and reduced restrike times. The cost of a pulse start metal halide luminaire and lamp may run from 5-10 percent more than a conventional luminaire/lamp combination but the cost may be easily justified by the improved performance.

Ceramic metal halide lamps are used when color rendering and color consistency are a priority. They achieve over 80 CRI by utilizing higher fill pressures and operating at higher temperatures. They also have the potential for longer life, with some expected to achieve significantly higher life ratings, more stable color, higher lumen output and better lumen deprecia-

tion characteristics than other metal halide lamp types. This will make these lamps more attractive choices in some industrial environments. At the time of publication, ceramic metal halide lamps are available in ratings from 39 to 400 watts.

Cost may become a determining factor in the choice between the widening selection of metal halide lamps and HPS lamps in the short term, but that must be fol- lowed closely and weighed against the benefits of the improved characteristics of the MH lamps.

5.2.2 High Pressure Sodium (HPS) Lamps

Most HPS lamps can operate in any position. The operating position has no significant effect on light output. Lamps are also available with diffuse coatings on the inside of the outer bulb to increase source luminous size or reduce source luminance. A diffuse coating, however, does not increase the CRI of the lamp.

HPS lamps have high lamp efficacy (lumenshatt), and long life. They are available in wattages from 35 to 1 O00 watts. The color rendering ability of HPS is not as good as metal halide lamps. Color improved HPS lamps are available but at a sacrifice in efficacy and life.

The life of an HPS lamp is limited by a rise in operating voltage that occurs over the life of the lamp. When the ballast can no longer supply enough voltage to reignite the arc during each electrical half-cycle, the lamp extinguishes. When it cools down, the lamp will again ignite and warm up until the arc voltage rises so that the ballast cannot support the arc. This cycling process occurs until the lamp is replaced. This cycling can cause annoyance and, more important, a variation in light output and distribution in a production area, underlining the need for a planned relamping program. Cycling also overworks the ignitor, eventual- ly causing it to fail.

HPS lamps are also available in a double arc tube configuration with two identical arc tubes contained within the outer envelope. These arc tubes are connected in parallel inside the lamp, but only one arc tube is started with the ignitor pulse. In the event of a momentary power outage, this dual arc tube lamp restrikes immediately when power is restored. Within about one minute, the lamp returns to full light output.

5.2.3 Luminaire Selection

Industrial HID luminaries are generally divided into two categories - High-Bay and Low-Bay. These categories are not well defined throughout the lighting industry. Therefore, for the sake of consistency in this Recommended Practice, they are defined as follows:

17


High-Bay luminaries designed to produce general illumination in the space where the application requires a spacing to mounting height ratio of 1 .O or less and where the mounting height is not less than 7.6 m (25 fi).

Low-Bay luminaries designed to produce general illumination in the space where the application requires a spacing to mounting height ratio greater than 1.0 and where the mounting height is less than 7.6 m (25 ft).

These are not rigid rules. Conditions will often dictate the use of high-bay or low-bay luminaries at mounting heights that vary from those indicated above.

5.2.3.1 High-Bay Luminaries

These luminaries generally use an HID lamp installed in a socket mounted below a ballast housed in some form of metal enclosure. Lumen distribution is controlled by a reflector, or refractor, installed in such a way that it captures most of the light emitted by the lamp and directs it in a concentrated pattern downward. The luminaire may have an enclosing plastic or glass cover attached to the bottom of the reflector or refractor to enclose the lamp and to protect against accidental damage. The cover may have a pattern of prisms to aid in the distribution of light from the luminaire. The luminaire design will usually dictate the use of either a clear or coated HID lamp, and the proper lamp selection is critical to the success of the lighting design. These luminaries may have an adjustable socket mount to permit relocation of the lamp within the reflector or refractor. This will allow some field adjustment of the luminaire distribution to meet specific condition of the installation. Care must be exercised in positioning the lamp. The lamp socket must be securely locked into place to ensure the position will not change during normal luminaire operation.

There are usually openings around the top of the reflector to permit some of the light to be directed upward toward the ceiling. Where conditions warrant, the luminaire may be gasketed to reduce the infiltra- tion of air-borne contaminants. Several methods have been developed to filter the air exchange between the inside of the luminaire and the room. This becomes more important if the luminaire operating cycle includes turning the luminaire off daily, which will accentuate the effects of warming and cooling on this air exchange.

Designers often recommend luminaire spacing that provides a strong overlap in the light distribution pattern to mitigate the effects of single lamp burnouts during the operating life of the system. Installing luminaries having a spacing criterion of 1.0 in a pattern

18

where the luminaries are actually located at approximately 0.65 times the mounting height will usually provide the desired overlap. If the luminaries are to be located closer together than dictated by the luminaries’ spacing criteria, a spacing adjustment should be considered when the lighting calculations are performed to assure the proper illuminance and lighting quality in the final installation.

5.2.3.2 Low-Bay Luminaries

The construction of low-bay luminaries is very similar to that of high-bay luminaries except the reflectors, or refractors, of the low-bay units are generally larger in diameter than the high-bay units and the low-bay units are usually fitted with a prismatic refractor cover on the bottom of the luminaire. The refractor will oíten drop down below the reflector to assure good distribution in a wider pattern. While this will allow a wider spacing criterion and better vertical illuminance, the potential for glare from the luminaire may increase. Often the larger diameter of these covers will permit light distribution over an area great enough to lower the luminance of the cover to a level acceptable to the occupants.

There have been several successful installations in high-bay applications where low-bay luminaries were used to improve the vertical illuminance of the tasks or to provide greater wall luminance, thereby improving the quality of the visual environment.

5.2.3.3 Other Luminaire Types

Industrial luminaries are manufactured in various forms for special purposes. HID luminaries with prismatic reflectors or full refractors are available to produce several distribution patterns: maximum distribution up, equal distribution up and down, or maximum distribution down. These can be used effectively in large spaces with light colored surface finishes to produce excellent vertical illuminance, good penetration into hard to light spaces within machinery, and a very comfortable visual environment.

Fiber optic luminaries and tubular guided illuminators are useful where light is necessary in spaces having hazardous atmospheres or in inaccessible locations. The illuminators can be located in more easily acces- sible spaces and the light “piped into the hazardous spaces or the difficult to reach locations.

All discharge lamps, fluorescent or HID, have accessory devices called ballasts for starting and stabilizing operation of the lamp. Detailed information should be


obtained from the ballast manufacturers at the time of project design because of the rapidly changing lamp and ballast technology. Specific ballast issues associated with industrial lighting that may arise in almost every project are included here.

6.1 Fluorescent Ballast Issues

Advances in solid-state, high frequency ballasts have improved fluorescent system efficacy and, to some extent, luminaire light delivery efficiency through improved performance of smaller diameter lamps.

Fluorescent lamp ballasts are available in a wide array of choices. The choices for “straight‘! fluorescent lamps include magnetic, electronic, instant start, rapid start and dimming ballasts. The following paragraphs attempt to give guidance in the selection process to designers, plant operating personnel and contractors. Factors which may impact on the correct choice of fluorescent lamp ballasts include environmental conditions, operating cycle, maintenance conditions, electrical power conditions and utility company requirements. It is often in the best interest of an end user to participate in ballast selection.

Magnetic ballasts have provided the foundation for discharge lamp operation since the first fluorescent and HID lamps were invented in the middle of the 20th century. Electronic ballast development began in the 1980s. Toward the middle of the 1990s, electronic ballast technology advanced to the point where the original problems were overcome. The drive for improved energy utilization has fueled a rapid conversion to the use of electronic ballasts in fluorescent luminaries. As we move into the 2Ist century, electronic ballasts will be the preferred fluorescent lamp operating accessory and it is likely their use will continue to increase.

Over the past several years, to assure proper operating characteristics for both the lamp and ballast, many fluorescent lamp manufacturers have either manufactured their own ballasts or formed alliances with ballast manufacturers to provide warranted lamphallast systems with system performance guaranteed for some period of years. It is important that the replacement lamps used during the maintenance of these systems be the same as the lamps originally installed to maintain the warranted performance. If this can not be assured, then any lamps substituted for the original types must be evaluated prior to lamp replacement to assure system performance will be maintained. The system warranty may be voided by such replacement.

It must be understood that the fluorescent lamp ballast market is in a constant state of development and it is suggested that manufacturer’s information be ref- erenced before a final ballast selection is made.

6.1 .I Ballast Circuitry

Four important characteristics of electronic ballast circuitry should be noted. These.are ballast factor, power . factor, crest factor and total harmonic distortion (THD).

Ballast factor provides a measure of the actual lamp lumen output when operated by the individual ballast in relation to the lumen output of the lamp when operated by a reference ballast. In other words, a percent of the lumens generated in application versus the lumens listed in the lamp catalog.

Power factor is a measure of how efficiently the ballast converts the voltage and current drawn from the system to usable lamp power.

Lamp Current Crest factor, is a ratio of peak lamp current to the root mean square (RMS) lamp current. It is an indicator of the lamp current wave shape, and is generally required by lamp manufacturers to be I 1.7 in order to achieve rated lamp life.

Total harmonic distortion (THD) is, in simplified terms, a measure of the amount by which the electric waveform is distorted by harmonic currents flowing in the electric power system lines. This distortion is generated, in large part, by non-linear electrical loads in a facility. In North America, the fundamental frequency is 60 Hz, the second harmonic is 120 Hz, and the third harmonic is 180 Hz, and so forth. For practical purposes, the third harmonic is usually the only one that will make a significant contribution and most of the harmonic current in the neutral of three-phase distribution systems is the third harmonic. This harmonic current will disturb utility power generation and, of more interest to the end-user, increase the current flowing in the neutral of three- phase distribution systems and, possibly, cause it to overheat and fail. Switching in modern solid-state electronic ballasts can cause substantial line-current har- monics when corrections are not implemented in the ballast. THD is, therefore, an important component of the ballast operating effect. The American National Standards Institute (ANSI) requires electronic ballasts to have a THD of no more than 32 percent. Most electronic ballasts sold in North America have THDs in the range of 5 to 30 percent and, therefore, should present no problems. There is a likelihood that electronic ballasts with a THD of less than l O percent can cause high inrush currents upon starting. Switching equipment installed on such circuits must be capable of withstand- ing this current. All these ballast characteristics must be carefully considered for each application.

Finally, it is important to be aware of the lamp holder (socket) configuration in luminaries using ballasts. A reputable luminaire manufacturer will select the proper lamp holder to perform properly with the ballast select-


Typical Industrial Areas in Which This Sound Level is Appropriate

Average Ambient Noise

Level of Interior 20-24 dE3 Offices, Control Rooms, Meeting

ed. If a luminaire, originally supplied with an instant start ballast, is to be refitted with a rapid start ballast, the lamp holder MUST be identified as suitable for the rapid start ballast, or the original lamp holder should be replaced with a holder suitable for use with a rapid start ballast. Ballast manufacturers recommend the use of knife-edge lamp holders when using electronic ballasts. High frequency lamp currents require a better connection than low frequency magnetic currents.

Sound Level Rating

A

6.1.2 Electromagnetic Ballasts

Warehouse or Storage Areas 25-30 dB B Shipping Dock, Equipment

Machine Shops, Foundries,

Rooms, Electrical Vaults, Large Parts Sub-Assembly

Printing Press Rooms,

31-36 dB C

37 dB or More D

Magnetic ballasts are available in full and reduced lumen output in both standard and energy saving types. The ballast must be compatible with the lamps to be used in the installation. This sounds obvious, but some energy saving lamps and ballasts will not operate properly in combination.

All indoor magnetic ballasts (except reactive types, which should seldom be used) should be Class P. These ballasts have a thermally activated reclosing switch to protect the ballast from overtemperature and tampering and to meet the requirements of the National Electrical Code (NEC) in the United States. Electromagnetic ballasts, as well as all other types, must be effectively grounded to meet code requirements. In areas where the ambient temperature may drop below 10°C (50"F), electromagnetic ballasts selected must be capable of starting and operating the associated fluorescent lamps at the lowest ambient temperature expected in the space.

By law, ballasts with PCB capacitors are no longer permitted in North America.

Sound ratings for electromagnetic ballasts vary depending on the type of lamps being operated. A ballast with the lowest available sound generating characteristics should be selected. This becomes particularly important in locations where added sound from lamp ballasts may be distracting. In an office or quiet location in the manufacturing facility, the ballast sound level should be " A where such a rating is available. Most T-12, T-1 O, T-8 and smaller diameter lamps not over 1200 mm (48 in) long will operate on sound level " A ballasts. Higher power lamp ballasts will generate more sound with 1500 ma, 2400 mm (96 in) lamp ballasts having a sound rating of "D. Figure 9 indicates the various ambient sound levels in which the four ratings should be used.

Because they operate at the normal power system frequency of 60 Hz, electromagnetic ballasts will be more likely to produce flicker and stroboscopic effects.

20

This can be an annoying and potentially dangerous characteristic in areas where there is moving machinery. If either of these conditions is a concern, electronic ballasts should be considered.

The US Department of Energy (DOE) Ballast Rule, officially adopted in 2000, was designed to raise the ballast efficacy for ballasts sold in new fluorescent luminaries by the year 2005, and as replacements in existing luminaries by the year 2010. A likely result of this legislation is rapid conversion of most common fluorescent ballasts in North America to electronic types.

6.1.3 Electronic Ballasts

Many of the problems encountered with electromagnetic ballasts are overcome with electronic ballasts. Along with their positive attributes, electronic ballasts may also introduce a few problems.

Since electronic ballasts operate at a frequency of 20 to 50 kHz, they will not produce annoying flicker or potentially dangerous stroboscopic effects. The sound rating for most of these ballasts is "A" and any sound that is generated is usually at a frequency that cannot be heard by humans. Electronic ballasts will operate most fluorescent lamps down to temperatures of -1 8°C (@ F).

In areas where infra-red control systems are used, the ballast operating frequency should be separated from the operating frequencies of these controls, which typically operate in the band between 3042 kHz, to prevent ballast generated interference. (Most ballasts manufactured today do operate above 40 kHz.) Electronic ballasts are available in either instant start or some version of rapid start configuration.

6.1.4 Instant Start Ballasts

Instant start ballasts are popular because they provide maximum energy savings and operate lamps in parallel, which means if one lamp fails, the balance of the lamps on that ballast will continue to operate. Instant start ballasts may shotten lamp life in situa-


tions where the lamps are frequently switched on and off. On circuits that have operating cycles of eight hours or more, lamp life is essentially the same when using either instant start or rapid start ballasts.

6.1.5 Rapid Start Ballasts

Rapid start lamp circuits are usually series-wired, which will extend lamp life for circuits switched often but cause increased energy consumption compared with instant start circuits. Therefore, a decision must be made, based on the operating cycles of the lamps, which wiring configuration best suits the individual needs of the application. There are various versions of the rapid start ballast circuit; for example rapid start, programmed rapid start or programmed- start. Each has specific advantages and the characteristics of each should be considered in the choice of ballast to be used. Rapid start ballasts, particularly the "program" modified circuits, will result in long lamp life regardless of the number of switching cycles.

6.1.6 Compact Fluorescent Ballasts

Much of the previous discussion of electronic ballasts also applies to compact fluorescent lamp (CFL) ballasts with the following additional comments.

The CFLs chosen should have four-pin bases. Two- pin CFLs are preheat lamps with starters and they are not suitable for use with electronic ballasts.

The electronic ballasts used with these lamps should have an end-of-life (EOL) circuit built into the ballast to reduce overheating of broken lamp cathodes and minimize the potential for lamps melting or cracking at end of life.

A range of CFLs is available in self-contained, screw mount base configurations, which can, if space is available and other conditions of use are met, replace incandescent lamps in many applications. Consultation with lamp and luminaire manufacturers is recommended before these substitutions are made. Note that power factor may be compromised in uni- tized magnetic screw-base systems.

6.1.7 Dimming and Two-Level Switching Ballasts

For additional energy savings, and where variable output fluorescent lighting is required, dimming and multilevel switching systems are available. Dimming ballasts will dim from 100 percent light output to several lower levels, such as 50 percent, 10 percent or 1 percent of full light output. The cost and the compatibility of these ballasts with various control systems varies, so it is recommended that a thorough investigation of the needs

and system compatibility be carried out before recom- mending fluorescent dimming systems. It is also recommended that lamp warranty and performance information be checked with the lamp manufacturer for lamps used with a particular dimming ballast. Multi- level switching is available using multiple ballasts in each luminaire or a single ballast per luminaire arranged for two level control. Careful investigation is required before such a system can be employed.

6.1.8 General Ballast Requirements

Figure 10 (see page 22) presents some of the electronic ballast considerations, and typical data, which must be evaluated before a final system decision is made. It is recommended that the specific numeric values listed be checked against current practice and equipment availability prior to purchasing.

6.2 High Intensity Discharge Ballast Issues

Ballast Factor should be considered when selecting HID luminaries. (See Section 6.1.1 .) The specific ballast factor of 0.9, 0.95 or occasionally 1.0 must be used in the calculation process as it directly affects the initial and maintained light levels from the luminaries under consideration.

All fluorescent and HID lamps exhibit negative voltage characteristics; that is, initially the impedance to the flow of current through the arc tube is high (before the arc is actually struck) and, as the arc is established in the lamp, the impedance goes down. Because the impedance drops so dramatically with the striking of the arc, an auxiliary device is required in the lamp circuit to limit the flow of current through the circuit. This device is the ballast. There are several circuit configurations for operating HID lamps. The power loss in an HID ballast is generally in the range of 5-15 percent. HID lamp ballasts using the autotransformer type of voltage input have the advantage of wiring arrangements that allow a tapped primary. This will permit the manufacturer to use one ballast production model for several different system voltages. While this may be of limited value to a final user, it will probably reduce the cost of production and inventory for the ballast manufacturer and may translate to a lower product cost. It may also be useful if the manufacturing facility has several locations on the site, which may have different voltages, because the tapped ballast primary would allow one replacement part to be used in several different plant locations.

This discussion will concentrate on those ballast circuits that are most common in industrial lighting applications. (See Figure 11 .)

21

ANSI / IESNA-RP-7-01

Ballast Ballast Characteristic TYP

Electro- Sound Rating Magnetic Minimum Lamp Starting Temperature

Recommended Values - Unless m e r s are Specified by Lamp Manufacturer

(<=less than; >=greater than) See Text 10°C (50°F)

I Maximum Ballast Case Temperature Standards Met

I 90°C (194°F) at Hottest Spot I UL935; CANICSA-22.2 No 74-92 and

Ballast Factor Power Factor Crest Factor Total Harmonic distortion (THD) Number of Lamps Operated

654; CBM; NEC; ANSIJEEE 82.1 >85% >90% 4 . 7 <20% 1 or 2 (Vsdly)

Electronic Sound Rating Minimum Operating Frequency 20,000 Hz Minimum Lamp Starting Temperature - 1 soc (0°F) Standards Met

< A (Usuaily Much Less)

ANSIAEEE C62.41; FCC Part 18

Figure 11. Typical circuits for operating high intensity discharge lamps.

Circuit Configuration Ballast Factor Power Factor Crest Factor Total Harmonic distortion (THD) Number of Lamps Operated

r - - - - _

(EMIRFI); CBM; ÚL; CSA; NEC Instant Start or Rapid Start >85% (May be lower for some lamps) >90% 4 . 7 GO% 1,2,3 or 4

Line I Ø Lamp

(a) High power factor reactor mercury lamp ballast

r-------- 1

I l I

I L. - - - - . - - . ----I Capacitor I \

Voltage L J

I \ a a b a

'\ II Lamp

Line

(b) High power factor autotransformer mercury lamp ballast

r -----

1 Core with

Lamp

Line

(c) Constant wattage autotransformer ballast for mercury lamps or peak-lead ballast for metal halide lamps

Caoacitor

Series line

I I \ I

r - 1

I I \ I L J

Lamp

(d) Constant wattage (isolated circuit) ballast for mercury lamps

(e) Constant current series regulator ballast for mercury lamps

22


6.2.1 Ignitors 6.2.3 High Pressure Sodium Ballasts

HPS lamp ballasts and pulse-start MH lamp ballasts differ from mercury vapor and most standard metal halide ballasts in that they contain an ignitor to provide the high voltage pulse required to start the lamp. The range of voltage pulses required to cold start HPS lamps varies from 2.5 - 4.0 kV. Pulse start metal halide lamps require about a 3 kV pulse for starting. The pulse circuit is designed to turn off after the lamp has successfully started by sensing the drop in open- circuit lamp voltage.

Instant restarting of hot lamps can be accomplished by increasing the ignition voltage. Voltage pulses of 10 - 70 kV are usually required to instantly restart a hot lamp. In most cases, instant restarting is limited to double-ended lamps because the increased voltage may result in arc-over between the lead wires, supports or base contacts in single-ended lamps.

6.2.2 Metal Halide Ballasts

The most common types of ballasts for MH lamps are Lead-Peaked for lamps over 175 watts and Lag Regulator (sometimes referred to as “HX or “HX- HPF for high power factor ballasts) for lamps rated less than 175 watts. Lead Peaked ballasts are very similar to Constant Wattage, Autotransformer (CWA) ballasts and, in fact, may be referred to as CWA ballasts in some literature. These ballasts provide relatively good voltage regulation and, because they contain a capacitor in series with the lamp, offer good power factor characteristics. Where supply voltage regulation is good, it may be possible to use a high power factor, reactor ballast which is usually less expensive than the more complex ballasts.

A lag-reactor ballast is essentially a metal core coil (the reactor) in series with the lamp. As long as the electrical system voltage is within the range of the lamp open circuit voltage and voltage regulation of the source is good, these ballasts can be satisfactory and are simple, small and inexpensive. The disadvantage is these ballasts have a power factor in the range of 50 percent. To improve the power factor, a capacitor can be added across the power leads, which will improve the power factor to the range of 90-95 percent.

Pulse-start metal halide luminaries require a special ballast with an ignitor, similar to those used in high pressure sodium ballasts. The ignitor is used to give the lamp the additional voltage “kick,” or pulse, it requires to start quickly. These luminaries may be useful where it is necessary to have more rapid restart of the MH lamps following a voltage outage or when the luminaries are first turned on. (See Section 5.2.2.1 for more advantages of pulse-start metal halide systems.)

HPS lamps show a rising voltage with rising lamp wattage. Because of this characteristic, maximum and minimum lamp voltage and wattage parameters have been established for HPS lamps (see Figure 12).

Maximum lamp wattage

i I I ” . , .

I I I I I I I i l

A 1 I r

O 67 84 95101 122 140151 Lamp voltage

Figure 12. Wattage and voltage limits for 400-W high pressure sodium lamps-HPS “Trapezoid.”

6.2.3.1 Magnetic Regulator or Constant-Wattage Autotransformer (CWA) Ballast

CWA ballasts are probably the most common for HPS lamp operation and consist of a voltage regulating circuit that feeds a current limiting circuit and an ignitor pulse generator required to start the HPS lamp. CWA ballasts provide good wattage regulation over a range of input voltage changes and good regulation for changes in lamp wattage. This type is a higher cost ballast than the reactor or lead circuit ballast and has higher power losses, but the added costs can often be justified because of the better lamp performance. A capacitor is usually included to provide good power factor correction. As with all auto transformer type ballasts, these may be suitable for use on a range of line voltage systems.

6.2.3.2 Lag or Reactor Ballast

These ballasts employ a reactor in series with the lamp designed to keep the operating characteristics of the lamp within the design trapezoid (see Figure 12). A starting ignitor is required and there is usually a power factor correcting capacitor added across the line or the primaty transformer winding. These ballasts provide good wattage regulation for lamp voltage swings but poor regulation if the line voltage varies more than 5 percent. These ballasts are the least costly HPS ballasts and have the lowest power losses.

23


6.2.3.3 Lead Circuit Ballast These HPS ballasts have a combination of induc- tance and capacitance in the lamp circuit. They decrease lamp current as the lamp voltage rises to keep lamp operation within the trapezoid. These ballasts provide wattage regulation for changes in both lamp wattage and line voltage of no more than 1 O percent. This ballast type is intermediate in cost and power loss.

6.2.4 Other HID Ballasts

There are other types of HID ballasts available. Among them are dimming ballasts and two-level switching ballasts (to allow selecting between two lamp lumen outputs without extinguishing the lamp). The designer should contact manufacturers for further information since the products available are develop- ing and the information changes rapidly.

HID ballasts used in industrial lighting can be differen- tiated by their lamp wattage regulation capabilities. Depending on the ballast type used, the lamp wattage can change as much as 2.5 percent.for each one percent change in line voltage. The best regulation ballasts available maintain lamp wattage to within a range of less than one percent for each one percent of line voltage change.

HID lamps have poor lagging power factor, which can be expressed as relatively high line current for the power load involved. Generally, the presence of a power factor correction capacitor in the ballast circuit solves this problem. Additionally, high pressure sodium systems, even with capacitors present, lose their power factor correction as the lamp ages. This is because lamp impedance changes with age, while the ballast electrical characteristics remain the same.

For specific detailed information on all types, always consult manufacturers’ ballast data.

7.0 DISTRIBUTION MODES

7.1 General Luminaire Characteristics and Performance

Industrial lighting luminaries include a range of types, housing incandescent, fluorescent and HID light sources. There are applications in industrial facilities for all of the above and for other specialized lighting equipment such as light emitting diode (LED), fiber optic, stroboscopic luminaries and more. This document will investigate only those general lighting luminaries commonly found in industrial environments, including luminaries using fluorescent and HID lamps.

For applications of other, more specialized luminaries in industry, refer to manufacturers’ publications that address those luminaries and applications.

7.2 Operating Considerations

Industrial luminaries must operate reliably in sometimes hostile environments. It is rare in industry to find locations where the space is conditioned and the mounting is as uncomplicated as recessed luminaries in a “tee-bar” ceiling. When those conditions do prevail, the same luminaire installations found in offices will often work. In many locations in the modern factory, there is minimal environmental control. Therefore, the luminaries must be capable of with- standing the ambient environmental conditions.

7.2.1 Electrical

The lighting specifier must know the electrical characteristics of the building to properly select the luminaire operating voltage. If incandescent lamps are used in any part of the building, it is necessary to provide a voltage compatible with the lamps used. In the case of fluorescent or HID systems, where a ballast provides the lamp voltage, the operating line voltage to the ballast is the designer’s critical consideration. The length of the wiring runs from the lighting panelboard to the farthest luminaire on the circuit can impact voltage selection. Wire length and size must be matched to the circuit lighting load to ensure that the last luminaire on the circuit will have suitable operating voltage. Voltage selection must also comply with the applicable electrical code requirements for maximum voltage to be used for luminaries at the prevailing mounting height.

7.3 Luminaire classifications

Luminaries are complete lighting units connecting lamp(s) and ballast(s) together with the parts designed to distribute the light, to position and protect the lamp, and to connect the lamps to the power supply. A common form of classification organizes luminaries into three application areas: residential, commercial and industrial. Within each application, source, mounting and construction, e.g., high-bay suspended metal halide lamp types, further classify luminaries. Another form of classification uses the luminaire intensity distribution. Chapter 7 in the IESNA Lighting Handbook, 9th Edition, describes the various classifications in detail. The International Commission on Illumination (CIE) provides a classification system based on the proportion of upward and downward directed light output. This system is usually applied to indoor luminaries:

0 Direct lighting - 90 to 100 percent of output downward

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0 Semidirect lighting - 60 to 90 percent of output

General diffuse lighting - downward and upward

0 Semi-indirect lighting - 60 to 90 percent of out-

Indirect lighting - 90 to 100 percent of output

downward

components of light about equal

put upward

upward

Most industrial applications require luminaries designed for a direct or semidirect light distribution. Luminaries with an upward component of light, usually 1 O to 30 percent, are preferred for most areas, because lighting the ceiling or upper structure reduces luminance ratios between luminaries and the background. The upward light reduces the perception of glare from the luminaries, mitigates the “dungeon” effect of totally direct lighting, and creates a more comfortable and cheerful environment. Industrial luminaries for fluorescent, HID and incandescent lamps are available with upward components. Good luminance relationships can be achieved with direct lighting equipment if the illuminances and room surface reflectances are high and if all components of the space have been carefully positioned (see Figure 13 (a) and (b), color insert).

Factors that lead to more comfortable and effective industrial lighting applications include:

Light-colored finishes on the outside of luminaries to reduce luminance ratios between the outside of the luminaries and the inner reflecting surface and light source.

0 Higher mounting heights to raise luminaries out of the normal field of view.

0 Better shielding of the light source by deeper reflectors, cross baffles, louvers, or well-designed diffusers. This is particularly important with high- wattage incandescent or HID sources and very bright smaller-diameter fluorescent lamps.

0 Selection of luminaries that contain specular or non-specular aluminum or prismatic configured glass or plastic for light control, so that luminaire luminance in the viewing zone can be limited.

0 Top and bottom openings in luminaries, which generally minimize dirt collection on the reflector and lamp by allowing convective air circulation to move dirt particles upward, through, and out the luminaire. Ventilated types of luminaries have proved their ability to reduce maintenance of fluorescent, HID and incandescent types of luminaries. Gasketed, dust-tight and dirt- and moisture-resistant luminaries are also effective in minimizing dirt collection on reflector surfaces.

Even gasketed luminaries, no matter how effective the gasket seal, have an exchange of air between the ambient environment and the inside of the luminaire. For particularly dirty areas, there are luminaries available that are fitted with various types of filters that allow the luminaire to “breathe” and still control the accumulation of dirt and contaminants on the inner surfaces of the luminaire. These luminaries should be carefully evaluated for effectiveness against the contaminated air in the application area in order to justify the added expense of “filtered luminaries.

Direct Lighting Equipment-Luminaries that direct 90 to 100 percent of their lumen output downward form a “direct” lighting system. Distributions of direct lighting equipment vary from ‘hidespread to “highly concentrated.’’ The widespread distribution types include diffuse and diff use-specular white reflecting surfaces. Aluminum, mirrored glass, prismatic glass, and other similar materials may be used to provide a wide distribution when the reflector is designed with the proper contour. Also, this type of light distribution is advanta- geous in industrial applications where mounting heights are relatively low or where a large number of the visual tasks are vertical or nearly vertical. Highly concentrated distributions are obtained with prismatic glass, mirrored glass and aluminum reflectors. In addition, this type of light distribution is useful where the mounting height is approximately equal to, or greater than, the width of the room, or where tall machinery or processing equipment necessitate directional control for efficient illumination between the equipment. This type of distribution produces relatively high horizontal illuminance in proportion to the vertical illuminance, and so may require the use of supplementary lighting when vertical illuminance is required on the visual task.

In making a choice between widespread and highly concentrated equipment on the basis of horizontal illuminance, a comparison of coefficients of utilization and spacing criteria for the actual room conditions serves as a guide in selecting the most effective distribution. The coefficients of utilization should be based on the best estimate of the actual ceiling, wall and floor reflectances as well as actual room proportions. However, if it is desired to determine illuminances at a specific location or task orientation, then a point calculation method should be used. This is particularly true for luminaries at high mounting heights.

Other Types of Direct Lighting Equipment-Where a low-brightness luminaire is required, a large-area Iow- luminance luminaire should be used; for example a diffusing panel placed on a standard type of fluorescent reflector, an indirect light hood or a completely luminous ceiling.

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Semidirect Lighting Equipment-This classification of distribution is useful in industrial areas because the upward component (1 O to 40 percent) is particularly effective in creating more comfortable seeing conditions. A variety of fluorescent and HID luminaries with this distribution are available and designed specifically for industrial applications. While the semi-direct type of distribution has a sufficient upward component to illuminate the ceiling, the downward component of 60 to 90 percent of the output contributes to good efficiency, particularly where occasional ceiling obstructions may lessen the effectiveness of the indirect component.

Industrial Applications of Other Distribution Classifications-The general diffuse, semi-indirect, and indirect systems are suitable for industrial applications where a superior quality of diffused, low-luminance illumination is required and where environmental conditions make such systems practical. An example of such an application is the precision manufacturing industry where there is a need for a completely controlled environment including lighting and air conditioning. Room suhace reflectances (initial and maintained) are important in the application of these lighting systems to ensure proper illuminance from the system throughout its life.

8.0 BUILDING CONSTRUCTION FEATURES THAT

NAIRE PLACEMENT INFLUENCE LUMINAIRE SELECTION AND LUMI-

Mounting of luminaries must conform to the building structure. Industrial luminaries are usually designed to be mounted to the surface of the structure or suspended by a hanging device. l h e skeletal framework used in the construction of industrial buildings forms interior subspaces called bays. The selection of luminaries, based upon their spacing criteria, is strongly influenced by the height of the bay. For this reason, industrial buildings are described as having low-bay and high-bay areas (see Figure 14).

Many modern industrial assembly buildings involve steel member construction with an outer shell or “tilt- up” concrete wall construction. The economies of this kind of project generally require a single floor building (and maybe a mezzanine) spread out generously over the site. This type of building may have a mixture of high-bay and low-bay areas.

There are certain types of structures, particularly in metals material producing and fabrication (stamping and forging), where large machines and overhead cranes are involved and where mounting heights can often exceed 15m (50 ft). l h e combination of low room cavity ratios and dirty environmental conditions

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\

Figure 14. This plant has a variation in height between high bay in the foreground and low bay at the rear of the assembly area. (Photo courtesy of Ruud Lighting.)

may require luminaries with narrow distributions. Closely spaced high-bay luminaries are required where the light is needed at or near floor level.

Since the structure of the building is a convenient location for power distribution, the structural bay often influences the luminaire pattern. This can either be in terms of the spacing module of the main structure, which sets a minimum spacing, or the secondary horizontal members like purlins, which are used to support the power distribution system and may also establish a set quantity of luminaries in each bay. Either way, the luminaire spacing may be determined by the structure. It is common to adjust the number of luminaries installed in a space to allow for a somewhat regular luminaire pattern that will compliment the structural building array. This approach is practical as long as the adjustment in the number of installed luminaries does not vary from the number required to achieve the designed illuminance, light distribution and lighting quality by more than 1 O percent. Lighting designers, then, must fine-tune their designs with respect to the target illuminance levels.

Luminaries that are properly designed to operate under the expected shock conditions should be installed in building locations where there is a probability of high levels of vibration. The luminaire mounting must be carefully designed to accommodate the


vibration. Accessories that are useful for these applications include spring mounting devices, lamp retain- ers to prevent lamps from vibrating out of the lamp holders, and safety chains to prevent the luminaire from vibrating loose and falling to the floor.

9.0 LIGHTING SYSTEM ECONOMIC ANALYSIS’

Good lighting must be responsive to the needs of the owner. Lighting systems must provide a lighted environment that allows workers to perform at the highest possible level, satisfy the aesthetic needs of the occupants, and must operate economically. “Economical” should not be confused with “cheap” or even “lowest first cost.” The lighting system that provides the lowest installed cost may result in poor worker performance, which leads to unacceptably high labor costs. Or, it may not provide a lighted environment to allow the workers to perform at a level that will allow the company to be as profitable as it should be. An economical lighting system is one which, when the first cost, operating cost, and system performance are all considered, provides the greatest practical benefits for the least total cost. This description of economical is often termed “cost-effective.”

The IESNA considers economic analysis to be a two level process. First-level provides a quick and inexpensive means of determining the costs of two, or more, lighting systems, relative to each other. While the cost to provide a first-level analysis may be low, the results are more subject to error than a more complete analysis would be and the longer the time frame under consideration in the study, the greater the potential for error. Second-level economic studies take into consideration many more conditions than first cost, such as operating cost, maintenance, and time cost of money. These also require a great deal more time to complete. The first decision that must be made is the level of confidence required and the acceptable study cost for the numbers coming out of the economic analysis.

After this has been determined, the study level can be established.

First-Level Analysis: First-level analysis requires relatively simple calculations that can usually be performed by “hand calculation methods and do not require the use of a computer program. Because these methods do not take into consideration the time value of money and do not usually provide the means to evaluate various maintenance and operating conditions, they yield only crude numbers, which may be valid for only a short time after the initial installation is completed. One way to determine if a first-level analy-

sis is adequate is to answer the question “what is the cost of a wrong answer?“

Probably the most common type of first-level analysis is the “Simple Payback” method. This method is designed to answer the question “how long will it take to recover the initial lighting system cost?” This is determined in the simple payback method by the formula: Equation 1

simple payback = incremental investment

In this equation, the “incremental investment” is the difference in the first (or installed) cost of the two systems, which are being compared. The “incremental annual cash flow” is the difference in the cost of energy and maintenance (including lamp replacement, energy cost, repair or replacement parts and the labor to accomplish the maintenance) for the two systems that are being compared. The method can be used to compare an existing system with a potential replacement system or two systems that are being considered for a new installation. In addition, the method may also be used to compare more than two systems but that may lead to even wider variance of results. A simple payback result is shown in Figure 15.

Ali first-level economic analysis, such as the simple payback method, suffer from a lack of consideration of many important elements of a complete analysis. The cost of money and equipment lifetimes need to be considered for a complete economic analysis.

incremental annual cash flow

There are other first-level methods of analysis available if such a study will provide the necessary information. Simple Rate ofßeturn is the inverse of Simple Payback, giving a simplified rate of return for the systems with the lower total costs. However, it suffers from the same problems of the Simple Payback method. The popular Cost of Light considers the cost per lumen for two different lighting systems by com- paring the owning and operating costs for each.

All of these systems have shortcomings if the real need is a complete economic analysis. The better solution, if more exact data is required, is to run a second-level analysis that will include many of the critical elements not included in the first-level analysis.

Second-Level Analysis: The distinguishing feature of all second-level economic analysis methods is the inclusion of the time value of money. Additionally, these methods allow extending the period of the analysis over many more years than is possible with a first-level analysis, often considering the costs for periods of twenty years. If a second-level analysis is required, quite often the end user’s financial depart-

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Systems Initial Incremental Additional Investment Change Annualized (in $000) (in $000) costs

(in $000) Base System 110 NIA 20

Alternate Sys. 2 130 . 20 13 Alternate Sys. 3 140 30 21

Alternate Sys. 1 120 10 17

Annual Simple System Payback Savings (in years) (in $000) NIA NIA 3 3.33 7 2.86 -1 No

Payback

Where the following definitions apply:

Column Heading System

Initial Investment

Information Contained in Column A listing of the number and description of each of the systems to be compared

The initial installed cost of each of the installed systems in thousands of dollars ($000)

Incremental Change from Base (in $000)

Incremental change in the initial installed cost of the alternate systems vs. the base system

Additional Annualized Cost (in $000)

The annual cost of operating and maintaining the system (energy, lamps, repairs, labor, etc.)

Annual Savings (in $000)

The difference between the annualized cost of the base system and the annualized cost of each of the alternate systems (minus sign {-} indicates alternate system costs more /year to operate than base system)

Simple Payback .

(in years) The number of years it will take to return the initial added investment in each of the alternate systems

Note that Alternate System 3 will never pay back the added initial investment cost because it costs more to operate Alternate 3 than it does the Base System.

ment or advisor will determine the calculation procedure and values to be used. The information in this section is provided to give the reader a general overview of the information that may be required for second-level economic studies.

The lighting and associated mechanical system information required to perform a second-level analysis is more comprehensive than required for first-level analysis. The information required for second-level analysis may include the following (see box top of next page):

In addition to these considerations, there are system costs associated with environmental issues such as hazardous waste disposal in the lighting system components that must be considered.

Once all of the necessary information has been gath- ered, the costs can be converted to equivalent annual costs for each of the systems under consideration.

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A decision must then be made as to whether the study should be performed in terms of present value or future value and an interest rate (or “opportunity “ rate, a term often used by financial professionals) must be selected. The cost is usually provided in consultation with the owner’s financial advisors.

There are many methods that the second-level economic analysis may take - Saving Investment Ratio, Internal Rate of Return, Net Present Value or, the most common method, Life Cycle Cost/Benefit Analysis. The actual method of economic analysis must be determined between the lighting system designer and the financial advisors. The calculation method for second-level economic analysis is beyond the scope of this Recommended Practice but further information is available from IESNA in the document RP-31-96, Recommended Practice for the Economic Analysis of Lighting.‘


Initial System Costs Lighting system material and labor cost Total lighting system power wiring cost Air conditioning to dissipate heat from lighting system (Tons)

1 st cost of air conditioning equipment Reduction in cost of heating equipment due to heat from

lighting system Utility incentives (reduced cost due to energy efficient

lighting) Other first costs Sales tax on equipment purchase Salvage value of lighting system at end-of-life

Owning and Operating Costs Lighting system energy costs Air conditioning energy costs Lighting system maintenance costs (lamps, ballasts, labor

to replace & clean, etc.) Air conditioning operating costs Heating system operating costs

Other annual costs

Annual insurance costs Annual property taxes on equipment Income tax effect (due to depreciation of equipment)

10.0 SPECIAL CONSIDERATION FACTORS

10.1 Lighting and Space Conditioning

The heat from lighting equipment is heat that is added to the normal space heating. For some manufacturing spaces, this heat must be considered as part of the cooling load. By using the lighting system as a return air path, or returning air from locations where the lighting is located, lighting heat can be exhausted before it affects cooling. Whether this happens as described depends on the type of HVAC system and how the particular space is heated and cooled. Conversely, lighting heat can be used for comfort heating in locations where it is required.

10.2 Classified Areas

Classified Areas are where flammable gas or vapors or combustible dust or easily ignitable flyings or fibers are or can be present. (See Figure 16, color insert.) These are defined in the National Electric Code (NEC) in the United States in terms of Classes (gas, dust) and Divisions, which define the conditions and manner in which the material is present. The National Fire Protection Association (NFPA) defines the hazardous nature of the space and the requirements for luminaries suitable for application in classified areas. The designer should check with the insurance carrier for the industrial site to determine the exact Class and Division for individual areas.

Hazardous Gas Normally Present (Class 1, Division 1) A considerable focus is placed on external or internal temperatures, or ‘7-number” of the luminaire. Internal temperature is usually the hot spot temperature of the lamp envelope. In the case of hazardous gases, the limiting temperature is on the exterior luminaire surface if the hazardous material is normally present “in quantities cuff icient to produce ignitable mixtures”

(Division 1). The ‘7-number” of the lighting equipment must always be less than the “flash point temperature” of the hazardous material in the area.

Hazardous Gas Not Normally Present (Class 1, Division 2) If the gaseous material is not normally present (Division 2), the limiting temperature is internal to the luminaire, usually the lamp envelope hot spot.

Hazardous Dust Normally Present (Class 2, Division 1); Hazardous Dust Not Normally Present (Class 2, Division 2), and Fibers and Flyings (Class 3, Division 1 and2) The limiting temperature is on the exterior of the luminaire.

A third party, such as an independent testing laboratory, usually “lists” a specific luminaire as being suitable for classified environment and allows the luminaire manufacturer to apply a label indicating suitability. Typically these are large red labels. The two most common mistakes in classified lighting applications are:

1. An area is defined incorrectly as being “hazardous” or a specific luminaire or rating is erroneously declared suitable for a specifically rated area.

2. An applied luminaire rating has critical temperatures that are too high with regard to the auto-ignition temperature of the hazardous material or rating category present.

The classified label may say that it is suitable for Class I, Division 2 applications. But it is the temperature for each wattage rating that determines whether that luminaire can be applied based on the auto-ignition temperature of the substance present.

The typical Class 1, Division 1 luminaire has a ballast compartment and a heat resistant tempered glass lamp enclosure. Configured this way the luminaire has almost the same optical characteristics as the bare lamp.

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Utilization can be materially improved with classified location luminaries by using optical refractors or extemal reflector accessories available from the manufacturer.

10.3 High Humidity or Corrosive Atmospheres

High humidity or corrosive atmospheres are likely to be present in at least some areas in a typical plant. Further, outdoor lighting locations may be exposed to rain, snow, fog, wind, high humidity and salt-laden sea air.

The usual methods to protect against these atmospheres include the use of materials that resist corrosion, special surface preparations and corrosion resistant coatings or paint such as epoxy, polyester or polyvinyl chloride. In addition, robust modes of paint application such as electro-static coating or powder coating may be used. Luminaries that have non-metallic outer housings are also available. Some luminaries for classified locations are constructed in a manner that makes them suitable for high-corrosion areas.

In the future, fiber-optics-based systems may find more application in classified and high corrosive areas because both the heat source and the material subject to corrosive attack are effectively removed from the space.

10.4 High Ambient Temperatures

Abnormally high ambient temperatures are often present in industrial applications, especially near the ceiling where the luminaries are installed. Industrial luminaries are available with ratings for ambient temperature conditions of 40" C, 55" C and 65" C (1 04" F, 131" F, 149" F). The temperature rating of the selected luminaire is important and should be at least as high as the temperature in which it is to operate during the warmest season of the year. The limiting factor can be any of several components within the luminaire. If the limiter is a ballast component, the ballast housing may often be remotely mounted in a cooler location.

Except for ignitor-start lamps (high pressure sodium and pulse-start metal halide), the only distance limita- tion to remote ballast location is the wire gauge. This is sized for the distance, according to the ballast manufacturer's recommendation, to hold voltage drops to a comfortable minimum.

With any system that has a pulse-igniter, the maximum distance the ignitor can be removed from the lamp is limited. In some cases the igniter can be placed in a compartment that has suitable heat sinking and remain with the optical portion of the luminaire (the other heat-sensitive components can be mounted remotely). Otherwise, a "long range ignitor" should be used to increase the remote distance. The ballast manufacturer should be consulted for exact limitations.

10.5 Low Ambient Temperatures

Abnormally low ambient temperatures are usually found in commercial food processing and distribution facilities. Temperatures become an issue if they are below 10" C (50°F) for fluorescent lamps, and -29" C (-20" F) for HID lamps. Fluorescent systems generally require a ballast for low temperature starting if the ambient temperature is lower than 10" C (50" F) for standard lamps and -18" C (Oo F) for 800 ma and 1500 ma lamps. At temperatures less than 20" C (68" F) fluorescent lamps stabilize at rated watts but at less than rated lumens. Enclosing the bulb-wall, either with a plastic sleeve or an enclosed optical area, will improve the lumen output. Depending on the type of enclosure and the ambient conditions, the lamp or lamps may heat up the enclosure to normal operating temperature to produce rated lamp lumens.

Most ignitor-start HID ballasts are rated to start a lamp (pulse-start metal halide or high pressure sodium) in temperatures to -40" C (-40°F). Temperatures below this require auxiliary incandescent sources, which warm up the interior of the luminaire until the HID lamp starts. These are usually coupled with a relay, which tums off the incandescent source when the HID lamp starts.

10.6 Clean Rooms

Clean room lighting uses entirely different luminaries than other industrial environments. Clean rooms are sealed, controlled environments designed to eliminate microscopic particles of a specified size. The particle may be dirt, which at a certain size (usually measured in microns) causes quality problems of the manufactured product, such as a silicon chip. The particle could also be an organism, such as a microbe that must be eliminated from an operating room. The Institute of Environmental Sciences (IES) categorizes generic clean rooms by a series of classifications based upon the number of micron particles found in a cubic foot of air inside the room. The categories start at 100,000 parts per cubic foot and get cleaner by factors of ten. Class 10,000, class 1,000, class 1 O0 and class 10 Clean Rooms are all defined by this organi- zation. Quite often, class 100 clean rooms are found inside class 1.000 clean rooms.

Clean room structure usually includes t-grid ceilings of a type not found outside this application. The t-grid is' of a larger cross-section, such as 1 ?" or 2 wide and is always gasketed in some fashion. Many of these ceilings are made for walking upon so that the fixtures and High Efficiency Particulate Air (HEPA) filters can be serviced from above.

There are four main types of luminaries used in clean- rooms:

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Gasketed recessed (troffer) fluorescent Tear-drop surface fluorescent Flow-thru recessed fluorescent Recessed T5 fluorescent integral to the T-grid

Gasketed recessed fluorescent luminaries are usually used in the class 100,000 and class 10,000 spaces, and the other three types are used as more and more of the grid-spaces are taken up with filters and cannot be occupied with luminaries.

In most of these construction styles, the important issues are that gasketing seals the room from the outside environment and that the outside surfaces are smooth and cleanable. Prismatic lenses, for example normally are installed “prisms-up” to present a smooth surface to the space.

10.7 Food and Drug Processing

Food and drug processing areas generally have additional requirements for construction and materials used in the luminaire. The requirements are documented by sanitation-regulating entities, such as the National Sanitary Foundation (NSF) or the US Department of Agriculture (USDA), and can classify different sections of the food processing area by the proximity of the luminaire to the food. Some classifications call for smooth exterior surfaces to eliminate areas for particle accumulation or bacterial growth. One constant is that glass cannot be exposed. This means that open-lamp and glass-enclosed luminaries are not suitable. In many food processing areas, scheduled pressure washing is required and therefore luminaries must be gasketed to withstand washing. Each facility’s pressure washing equipment is different, producing different pressure and flow rates. This information should be obtained from the plant engineering office and luminaire capabilities matched to it. Paint is required to be non-toxic and environmentally neutral, in case it chips or flakes off. Unfinished stain- less steel luminaries are popular in the extremes of this type of application.

The color rendering properties of light sources used in food inspection areas are important when examina- tion is based on color appearance. (See Section 3.8.)

11 .O GENERAL LIGHTING

General lighting is intended to provide substantially uniform illumination throughout an area, exclusive of any provision for special local requirements. Uniform illuminance is the distribution of light such that the maximum and minimum illuminance at any point is not more than one-sixth above or below the average

level. There may be perceptible differences in illuminance if suggested spacing criteria values are exceeded. Recommended luminaire spacings can be determined from published spacing criteria. When calculating values such as uniformity and average light levels for general lighting the grid spacings should be sufficiently small to give accurate values.

Production functions situated close to walls should have a general illuminance comparable to that in the central area. The distance between the wall and the adjacent luminaries should not exceed one-half the spacing between those in the central area. Closer spacing is often preferred.

General lighting defined by the building structure may not be adequate for some difficult visual tasks or situations where there are obstructions. Here, supplementary task lighting may be necessary.

One design approach is to provide general lighting for circulation, safety or simple visual tasks, with the addition of supplementary lighting directly adjacent to an assembly line, workbench or inspection area.

12.0 SUPPLEMENTARY TASK LIGHTING

Difficult visual tasks, such as inspection, often require a specific quality and quantity of light that cannot readily be obtained by general lighting methods. Supplementary luminaries are often used to:

o provide higher illuminances o direct attention on small or restricted areas o achieve a certain luminance o provide a specific color rendition o permit special aiming or positioning of light

o reveal the details of the visual task. sources to produce/avoid highlights or shadows

The specific requirement of each visual task need to be evaluated before supplementary task lighting can be specified. Simply adding lighting at the task with no consideration for the light reflecting or transmitting characteristics of the object(s) observed will be inef- fective. An improvement in the visibility of the task will depend upon improvement of one or more of the four fundamental visibility factors - luminance, contrast (chromatic or achromatic), size and time.

The planning of supplementary task lighting also requires consideration of the visual comfort of workers performing the task and other workers in the immediate area. Supplementary equipment must be carefully shielded to prevent glare for the user and neighboring workers. Luminance ratios should be

31


carefully controlled. Ratios between task and immediate surroundings should be limited, as recommended in Figure 2. To attain these ratios it is necessary to coordinate the design of supplementary task lighting and general lighting. (See Figure 17 (a) and (b).)

12.1 Luminaries for Supplementary Task Lighting

Supplementary task lighting luminaries can be divided into five major types according to candlepower distribution, luminance and other construction features. A graphic representation of the different types of supplementary lighting is shown in Figure 18.

Figure 18. Typical configurations of supplementary lighting luminaire types.

Type S-l- Directional. Includes all concentrating luminaries. Examples are reflector or narrow-beam spot lamps Or units that employ concentrating or colhat- ing reflectors or lenses. Also included in the group are concentrating linear units such as a well-shielded fluorescent lamp within a concentrating reflector or lens, or both.

Figure 17. (a) A combination of general and task lighting provides uniform illuminance for assembly of electronic Printers. (Photo Courtesy of Genlytmhomas.)

Type S-Il - Spread, High-Luminance. Includes small-area sources, such as incandescent, tungsten- halogen or high-intensity discharge. An open-bottom luminaire that has a deep-bowl reflector with a diffuse reflecting surface is an example of this type.

Type S-Ill - Spread, Moderate-Luminance. Includes all fluorescent luminaries having a variance in luminance greater than 2:l across the light-emitting surface.

Type S-IV - Unifonn-Luminance. Includes all lighting units having less than 2:l luminance variance across the light-emitting surface. Usually this luminance is less than 6800 cd/m2. An example of this type is a group of fluorescent lamps behind a diffusing panel, or con- cealed fluorescent lamps producing a linear arrange- ment of reflected light on a diffuse reflective surface.

Type S-V - Uniform-Luminance with Pattern. Includes all units described in Type S-IV except that a pattern of stripes is superimposed over the lighted image. An example of this is a group of bare fluorescent lamps, arranged in a regular, directional spacing, with a black background or non-reflective surface between the lamps. This unit is used to project a precise series of high-contrast lines across the surface of the task or the object being inspected.

12.2 Portable Luminaries

Wherever possible, supplementary luminaries should be permanently mounted in the location where they can produce the best lighting effect and maintenance

32

Figure 17. (b) and for computer workstations in a production area (Photo courtesy of Hubbell Lighting.)

afier assembly. Portable equipment, however, can be used.to good advantage where it must be moved in and around movable machines or objects, as in air- plane assembly, or in maintenance operations where internal surfaces must be viewed. (See Figure 19.) The luminaries must be mechanically and electrically rugged to withstand possible rough handling. Lamps should be guarded and of the rough-service type. Guards or other means should protect the user from excessive heat. Precautions, such as the use of ground fault circuit interrupters for personnel protection, should be taken to prevent electrical shock, and electrical connections must be suitable for the service to which they will be subjected.


fl

Figure 30. Storage of

materials in the center

oor area of a production

facility. (Photo

courtesy of Holophane.)

Fiaure 32. Aimable floodlight luminaries. (Photo courtesy of Ruud Lighting.)


Figure 13 (a) and (b). Light colored surfaces ensure good luminance relationships.

Figure 13(a) (Photo courtesy of Holophane.)

Figure 13b (Photo

courtesy of Hubbell Lighting.)

II


Figure 16. Dust-tight luminaries on an outdoor crane assembly. (Photo courtesy of Phoenix Products Company, Inc.)

Figure 23. Uniform lighting

is provided for horizontal work

surfaces in a packaging area. (Photo courtesy

Holophane.)

III


Figure 24. Luminaries located over the floor storage area provide horizontal illuminance for identification of product to be shipped, while luminaries close to the door openings provide light for loading trailers. (Photo courtesy of Holophane.)

Figure 29. Careful placement of overhead luminaries and a built-in shield over the LCD display insure that there are no reflections on the tilted control panel. (Phc courtesy of Holophane.)

IV

Figure 19. Small portable luminaries provide localized lighting on the task.

12.3 Classification of Visual Tasks and Lighting Techniques

Visual tasks requiring supplementary lighting are unlimited in number but can be classified according to certain common characteristics. The detail to be seen in each task group can be emphasized by the application of certain lighting fundamentals. Figure 20 classifies tasks according to their physical and light controlling characteristics and suggests lighting techniques for good visual perception. It should be noted when using Figure 20 that the classification of a visual task is based on the task?s characteristics and not on its application. For example, on a drill press, the visual task is often the discernment of a punch mark on metal. This could be a specular detail with a diffuse, dark background, classification A-3 (b) in Figure 20. Luminaire types S-Il or S-Ill are recommended. S-Il on an adjustable arm brack- et may be a practical recommendation when space is limited. Several luminaire types are applicable for many visual task classifications, and the best luminaire for a particular job will depend upon physical limitations, possible locations of luminaries and the size of the task to be illuminated.

~~ ~ ~~~~~~

13.0 SPECIAL EFFECTS AND TECHNIQUES

13.1 Color Contrast

Color as a part of the seeing task can be effectively used to improve contrast. While black and white may be the most desirable combinations for continual tasks such as reading a book, it has been found that certain color combinations have a greater attention value. Black on yellow provides the maximum visual contrast; and the next combinations in order of prefer- ence are green on white, red on white, blue on white, white on blue, and, finally, black on white.


13.2 Inspection Techniques

The color of light can be used to increase contrast by either intensifying or subduing certain colors inherent in the seeing task. To intensify a color, the light source should be strong in that color; to subdue a color the source should have relatively low spectral power in that color. For example, it has been found that using a bluish light such as a daylight fluorescent lamp can emphasize imperfections in chromium plating over nickel plating.

Three-dimensional objects are seen in their apparent shapes because of the shadows and highlights resulting from a strong directional component in the incident light. This directional effect is particularly useful in emphasizing texture and defects on uneven surfaces. (See Figure 21 .)

Figure 21. Directional lighting (right) reveals a pulled thread unseen by diffuse lighting (left.)

Silhouette is an effective means of checking contour with a standard template. Illumination behind the template will show brightness where there is a difference between the contour of the standard and the object to be checked.

Fluorescence under ultraviolet radiation is often useful in creating contrast. Surface flaws in metal and nonporous plastic and ceramic parts can be detected by the use of fluorescent materials.

The detection of internal strains in glass, lenses, lamp bulbs and transparent plastics may be facilitated by transmitted polarized light. The nonuniform spectral transmittance of strained areas causes the formation of color fringes that are visible to an inspector. With transparent models of structures and machine parts, it is possible to analyze strains under operating conditions.

33


Figure 20. Classification of Visual Tasks and Lighting Techniques.

Classification of Example Lighting Technique Visual Task

General Description Lighting Requirements Luminaire Type Luminaire Location Characteristics

PART I-FLAT SURFACES ~~~

A.-OPAQUE MATERIAL

1. DIFFUSE DETAIL AND BACKGROUND

a. Unbroken surface Proofreading printed text Prevent direct glare and S-Il or S-Ill

b. Broken surface Scratch on unglazed title Emphasize surface breaks S-l shadows

At 45" to page, opposite

At grazing angle to surface viewer

2. SPECULAR DETAIL AND BACKGROUND

a. Unbroken surfaces Dents, warps, uneven Emphasize uneven surface surfaces

b. Broken surface Scratch, scribe, engraving, Create contrast of cut edge punch marks against specular surface

mark

c. Specular coating Inspection of finish plating Emphasize unplated surfaces over specular over specular base background material

3. COMBINED SPECULAR AND DIFFUSE SURFACES

s-v So image of sourceipattern is reflected to viewer

S-Ill or S-IV when not Source/pattern is reflected to viewer and edge or

is dark

image toward viewer

practical to reorient task

S-IV with color of source selected to create maximum color contrast between two coatings

To reflect large, diffuse source

a. Specular detail on diffuse, light background

diffuse, dark background

c. Diffuse detail on specular light background

d. Diffuse detail on specular dark background

b. Specular detail on

Reflective varnish or foil Produce maximum contrast S-Ill or S-IV applique on matte paper stock

dull or dyed metal

without veiling reflections

Punch or scribe marks on Create uniform, bright reflection S-Il or S-Ill on detail

Graduation marks on a Create uniform, low-brightness S-lll or S-IV steel scale; reverse print on a glossy stock background

paint against dark background

reflections in specular

Soapstone marks on black Produce high-brightness detail S-Il or 5-111

Off-center so image of source does not reflect directly

So that light reflects from detail

So that image of source is reflected toward viewer

So that image of source is not reflected into view

B. TRANSLUCENT MATERIAL

a. With diffuse surface Frostedetched glass or Visibility of surface detail S-Il or S-Ill plastic, lightweight fabrics, hosiery

Visibility of detail within the

Visibility of surface detail

Visibility of detail within the

S-l or S-IV material

b. With specular Scratch on opal glass or surface plastic

S-Il, S-ill, or S-IV material

Treat as opaque, diffuse surface (see A.l)

Backlight through material (see Fig. 19-1 5f and n)

Treat as opaque, specular (see A.2)

Backlight through material (see Fig. 19-1 5f and n)

C.TRANCPARENT MATERIAL

Clear material with Plate glass; plastic To produce visibility of details S-V and S-I specular surface glazing sheet within the material, such as

bubbles and details on the surface, or scratches and waviness

Transparent materials should move in front of Type S-V then in front of black background with Type S-l directed to prevent reflected glare

34


Figure 20 Continued


~


D. TRANSPARENT OVER OPAQUE MATERIAL

a. Transparent ma- Instrument panel Visibility of pointer and scale S-I terial over diffuse background from the scale background

without veiling reflections

or cover

the transparent coating or on the opaque base material

Emphasize uneven surface Visibility of detail on or in

transparent material

Varnished desk top Visibility of detail on or in S-IV

S-l b. Transparent ma- Glass mirror terial over specular background

Visibility of detail on specular S-IV background

So reflection of source does not coincide with the angle of view (see Fig 19-1 50)

So that image of source and pattern is not reflected to the eye (see Fig. 19-15)

So reflection of source does not coincide with the angle of view the mirror should reflect a black background

So that image of source and pattern is reflected to the eye (see Fig. 19-1 51)

~

PART Il-THREE-DIMENSIONAL OBJECTS

A. OPAQUE MATERIAL

1. Diffuse detail and Dirt, checking, cold-flow or To emphasize detail having S-Ill or S-Il (standard To prevent direct glare and background blow-holes in castings poor contrast source) shadows (see Fig.

19-15h) "Black-light" source when To direct ultraviolet

object has a fluorescent coating to be inspected

radiation to all surfaces

S-l (standard source) To emphasize detail by means of highlight and shadow (see Fig. 19-150)

2. Specular detail and background

a. Detail on the Dent on silverware or To emphasize surface s-v To reflect image of source to surface chrome variation eye (see Fig. 19-159)

To reflect image of source to over underplating plated of color eye (see Fig. 19-1 59)

b. Detail in the Scratch on watch case To emphasize surface break S-IV To reflect image of source to eye (see Fig. 19-1 5m)

Inspection of finish plating To show areas not properly S-V plus proper selection

surface

3. Combination Specular and diffuse

a. Specular detail on Scribe marking on casting To make line reflect light over S-Ill or S-Il Adjust in relation to task for diffuse background dull background best visibility (adjustable

luminaire required) Overhead to reflect image of

source to.eye (see Fig. 19-1 5j)

b. Diffuse detail on Micrometer scale To create luminous back- S-IV or S-Ill Position with axis normal to specular ground against which dark axis of micrometer background scale markings are in high

contrast

contrast to dull impurities

Coal picking To make coal glitter in S-l or S-Il To prevent direct glare

35


Figure 20 Continued



B.TRANSLUCENT MATERIAL

1. Diffuse surface Lamp shade To show imperfections or S-l

15f) 2. Specular surface Glass enclosing globe To emphasize surface s-v

To check homogeneity s-IV

irregularities in material

irregularities

15nì

Behind or within object for backlighting (see Fig. 19-

Overhead to reflect image of source to the eye (see Fig. 19-1 5m)

Behind or within object for backlighting (see Fig. 19-

~~ ~~

C.TRANCPARENT MATERIAL

Clear material with Bottles, glassware empty To emphasize surface irregu- S-l Directed obliquely at objects specular surface or filled with clear liquid larities

To emphasize cracks, chips, S-IV or S-V Behind or within object for backlighting (see Fig. 19-1511). Motion of light source or object helpful

or foreign particles

Successful inspection of very small objects is greatly improved by viewing them through lenses. For production work, the magnified image may be projected on a screen. Because the projected silhouette is many times the actual size of the object, any irreg- ular shapes or improper spacings can be detected readily. Similar devices are employed for the inspection of machine parts where accurate dimensions and contours are essential. One typical device now in common use projects an enlarged silhouette of gear teeth on a profile chart. The meshing of these production gears with a perfectly cut standard is examined on the chart.

There are occasions when moving parts must be inspected or studied while they are operating. Stroboscopic illumination can be effective in this process by adjusting the rate of “strobe” to stop or slow the apparent motion of constant-speed rotating or reciprocating machinery. Stroboscopic lamps give flashes of light at controllable intervals (frequencies). The flashing can be so timed that when the flash occurs, an object with rotating or reciprocating motion is always in exactly the same position and appears to remain stationary. This technique can be very effective in allowing inspection of rotating parts without the necessity of stopping the process.

There is a potentially dangerous stroboscopic effect unintentionally produced by fluorescent and HID lamps and other sources operated on magnetic ballasts when flicker occurs on rotating equipment such as drilling, milling and lathe machines. At some rota- tional speeds, these parts can appear to be stopped 36

when, in fact, they are rotating at a dangerous speed. For some optional considerations, refer to the Section 3.7, Flicker and Strobe. The use of electronic ballasts to operate fluorescent lamps at high frequency can virtually eliminate flicker and strobe effects.

14.0 EMERGENCY, SAFETY AND SECURITY LIGHTING

Each of these subjects is covered at some length in Chapter 29 of the IESNA Lighting Handbook, 9th Edition. Reference to that chapter is recommended for further details on the design and selection of hardware for these very important systems.

14.1 Emergency Lighting

Locating exit and unit emergency lighting equipment can be improved when the designer visualizes how occupants will need to move through the space in an emergency. Buildings are usually large, complex and subject to materials being moved in and out continuously. In the event of an emergency where illumination is lost, it is likely that a worker could become confused. Emergency lighting requirements are often covered in codes or local ordinances that detail the levels of illuminance required, the duration of the lighting in the event of a loss of power, and the types of power sup- plies that are acceptable to “the authority having juris- diction.” Reference to these codes and ordinances is essential to ensure compliance with them.


Hazards Requiring Visual Detection Normal Activity Level

In addition, it may be helpful for lighting designers to put themselves in the place of building occupants and mentally walk through the facility to ensure they have provided lighting for exit and emergency egress and all foreseeable conditions.

Degree of Hazard Slight High

Low High Low High

Often, in industrial areas, presses, conveyors and other obstructions can defeat the emergency equipment, or obscure signage. A tour of the facility after occupancy may be necessary to satisfy all parties that the emergency lighting is satisfactory. Final adjustments to the system are often necessary to accommodate unexpected pieces of machinery or owner furnished obstructions installed during the project, which can change the effectiveness of the originally designed emergency lighting.

Illuminance Levels Lux Footcandles

14.2 Safety Lighting

5.4 11 22 54 0.5 1 2 5

Unlike emergency lighting, safety lighting is required at all times when the building or outdoor space is occupied. This ensures the occupants’ ability to move safely throughout the facility without danger. In industrial facilities there are many obstructions, potential danger from moving equipment and manufactured goods, and hazards associated with the manufacturing process. Minimum lighting for safety is recommended in Figure 22.

These values represent absolute minimum illuminances at any time and location where safety is related to visibility and they may require modification in some instances to ensure proper visibility in particularly hazardous locations. Care must be taken in the design of industrial lighting systems to guarantee the system will provide not only the necessary illuminance for the tasks to be performed but will also adequately indicate dan- gers and hazards within the facility. In addition, the lighting should be free of glare, shadows and extreme illuminance changes which could contribute to accidents.

Lamp selection is important in planning lighting for safety to ensure proper rendering of the safety colors

Figure 22. Illuminance levels for safety.

used throughout the facility. Many industries use color as an indicator of danger and the selection of a lamp which does not accurately render all of the colors within the facility can compromise the identification of these safety indicators by the occupants and lead to dangerous conditions.

It may be a code requirement that HID lighting systems have at least some of the luminaries fitted with auxiliary incandescent lamps to provide light during warm-up or re-strike times.

14.3 Security Lighting

In an industrial facility security lighting is usually required for protection of property, to discourage tres- passers and to provide a means for guards to identify employees during shift changes. Security lighting should be designed in consultation with the owner and his personnel responsible for the safety of property and employees. Consulting with local law enforcement departments can also aid in the design of a security lighting system to ensure that the lighting will aid, and not hinder, those officers (and private security personne1)’in the performance of their duties.

Security lighting methods for interior and exterior installations are discussed at length in Chapter 29 of the IESNA Lighting Handbook, 9th Edition,and reference to that chapter is recommended.

15.0 LIGHTING FOR SPECIFIC TASKS

The lighting requirements for specific tasks can be similar in a wide range of different industries. Whether the task occurs in a steel plant, machine shop or electronic assembly facility, the same lighting considerations apply for that task. In past editions of this Recommended Practice, consideration has been given to the lighting requirements in specific industries. It is now felt the specific industry may be less

These values represent absolute minimum illuminances at any time in locations where safety is related to visibility. (Note: the illuminance conversion used here is 10.76 lux = 1 fc.) However, in some cases higher levels may be required (such as where security is a factor). In other conditions, especially involving work with light-sensitive materials such as photographic film, much lower illuminances may be used. In these cases, alternate methods of ensuring safety must be employed.

37


important than the requirements for lighting of a specific task. For those who are looking for specific industry lighting recommendations, refer to Annex A-2.

15.1 Molding of Metal and Plastic Parts: Discussion of Lighting and Equipment Choices

Metal castings and plastic parts are made in a variety of sizes and shapes. Some are made to very close tolerances; others require less accuracy. The lighting requirements for molding operations vary with the required accuracy and the severity of the seeing task. A constant, however, is that foundry mold rooms and die-casting operations tend to be dirty, requiring careful selection of luminaries, while injection molding is a relatively clean process.

Maintenance in foundry and die-casting operations may be minimized by the use of ventilated or enclosed and gasketed luminaries. Some luminaries have filters, which permit "breathing" but minimize the ingress of dust. Best practice dictates the use of the minimum quantity of luminaries to provide the recommended illuminance and light distribution at the point of lowest lamp output and highest dirt accumulation.

In areas where injection molding operations occur, lighting can usually be provided by ventilated industrial luminaries. Painting the ceilings and walls with a highly reflective paint finish will increase the benefits of an uplight component.

Melting, molding and coremaking usually involve equipment with nonspecular surfaces. Where such work is done in high-bay areas, high intensity discharge luminaries may be installed without concern for the introduction of reflected glare.

15.1.1 Foundry Molding (Sand Casting)

The molding process involves forming molds from treated sand. The visual tasks are:

Inspecting the pattern for foreign material Setting the pattern in the flask and packing sand around it

0 Removing the pattern and inspecting the mold for loose sand and for accuracy of mold contour Inserting core supports and cores (the operator must be able to see the core supports) Smoothing mold surfaces, checking core position and checking clearance between parts

The size and detail of the tasks may vary. The small- est task has a visual angle of about 1 O minutes of arc (1/6") corresponding to the size of separate grains of sand A defect involving the misplacement of only five

or six grains of sand will cause imperfections in small castings. The more exacting seeing tasks are repeti- tive and of interrupted and short-time duration.

Lighting should be designed for the intermittent, critical seeing of materials that have low reflectances and unfavorable contrasts. The varying depths of mold cavities demand adequate illumination without harsh shadows.

Deep pit molds require additional consideration in planning proper lighting. The walls of the pit may block some of the light from the general lighting system and result in shadows and lower luminance, especially on the vertical surfaces of the molds. Visibility in the pit areas will benefit from the installation of additional general lighting luminaries, located to avoid conflict with materials handling equipment.

To improve visibility within the mold, placing white parting sand around the opening sometimes increases contrast. When weights are used, the opening in the weight indicates the general location of the pour- ing basin.

15.1.2 Molding Parts of Die-cast Aluminum and Injection Molded Plastic

The molding process involves forming parts from machined steel molds, or dies. The molds can be single or multiple cavity, but have two halves, completely encasing the part. The visual tasks are:

0 Inspecting the mold for foreign material 0 Applying the mold-release agent to the die 0 Closing the die and actuating the mold cycle 0 Removing the part 0 Performing secondary at-mold operations 0 Stacking or packaging of parts for material

handling

Lighting should be designed for the intermittent, critical seeing of materials that have low and high reflectances and unfavorable contrasts. The varying depths of mold cavities demand adequate vertical illumination that does not produce harsh shadows.

Proper general illumination contributes to safety. The eyes of the workers often become adapted to the bright, molten metal contrasted with dark surroundings. This adaptation may cause difficulty in seeing any obstructions on a poorly illuminated dark-colored floor. Adequate lighting reveals such obstructions.

15.1.3 Inspection of Sand-castings

Quality control depends largely on visibility. A casting meets the specified tolerances when:

38


Patterns are carefully checked against the

Flasks are inspected for fit Cores and molds are inspected for size, accuracy and alignment Core clearances are gauged prior to mold closing Castings are checked against templates and gauges Surfaces are inspected and defective castings are culled

drawings

Inspections are generally conducted at intermediate stages during the manufacture of the product. The inspections at some stages are either combined with the functional operation or performed in the same area. The type of inspection will dictate the proper quality and quantity of illumination.

An inspection of the cores by the coremaker is performed prior to baking. Later, the castings may be inspected and, if necessary, scrapped by the shake-out handlers or by the grinder operators, avoid- ing subsequent waste of labor on defective parts. Proper lighting will allow this inspection to be done quickly and effectively at this stage of production. Small castings are frequently inspected and sorted simultaneously.

15.1.4 inspection of Die-castings and Opaque Injection Molded Plastic Parts

Most parts of this type have specular or semi-specular surfaces, against which flaws are seen under category s-1 V supplementary lighting (see Figure 18.) Parts that have a matte (or heavier) texture in the mold are inspected much like sand castings, and have similar lighting requirements.

In sorting areas, a simple, general lighting system of ventilated fluorescent industrial luminaries may be mounted 1.2 m (4 ft) or more above the sorting table or conveyor. Atmospheric and maintenance conditions will determine the type of luminaries (open, enclosed or filtered) to be used.

For medium inspections, fluorescent luminaries may reduce reflected glare and improve diffusion of light. Medium-fine and fine inspection sometimes require special lighting equipment.

15.2 Parts Manufacturing and Assembly

Incoming Raw Materials. Raw materials are delivered to manufacturing facilities by truck or rail shipment. Both open-top and closed-top vehicles may be used. The visual task is to identify the materials and corre- late the material and shipping documents. General lighting with supplementary portable lighting for trailer or rail car interiors is required.

Active Storage Areas. Raw materials are often unloaded in the receiving areas by lift trucks or overhead cranes. They are transported to the active storage areas or directly to the production process by the same means. The visual task is to identify the materials (labels or markings) from the cab of an overhead crane or lift truck and to move the materials and deposit them at a designated location. Lighting requirements include general lighting with vertical illuminance for identifying labels and markings and horizontal illuminance for reading pick tickets.

Parts Manufacturing Processes. Several different types and sizes of parts using many unique processes may be manufactured in a single plant. The designer should refer to other sections of this document for major activities that occur in manufacturing plants such as machining, sheet metal fabrication, and casting. A number of different tasks may be performed. These are described under their own subheadings. General lighting is required with properly positioned supplementary lighting in areas or on equipment.

Parts Assembly. In many manufacturing plants, individual components are assembled into subassemblies. The assembly process combines manual, semiautomatic and automatic activities. The visual tasks are to select, orient, install and fasten a component to the subassembly. General lighting with supplementary lighting added to specific work station positions will help to reduce shadows.

Testing. Highly diversified and complicated procedures and test equipment determine compliance with design specifications for many subassemblies. Testing activities are manual, semiautomatic and automatic. The visual tasks are to secure the assembly to the testing device; to perform tests on electrical or mechanical connections; to run tests and read gauges and meters; to perform mechanical or electrical adjustments as required; to complete test reports; to disconnect and remove the assembly from the testing device. General lighting and properly positioned supplementary lighting are required.

Common tasks in manufacturing facilities include the manufacture of parts and the joining of those parts into larger sub-assemblies. Some of the important seeing tasks and typical lighting systems are as follows:

Final Inspection. Inspection determines whether the manufactured part or subassembly is in total compliance with the design specification. The visual tasks are inspecting the part or subassembly for specifica-

39


tion compliance and to verify that all intermediate inspections and tests are satisfactory. General lighting with supplementary lighting to inspect the part or subassembly is required. Note that good color rendering light sources should be used.

Packing. Parts are manually or semiautomatically placed in boxes, containers or racks for shipment. The visual tasks are to identify the part and place it in a destination-designated shipping container or rack. General area lighting is required. (See Figure 23, color insert.)

Shipping. Parts may be shipped to other plants or warehouses in enclosed rail cars and trucks. Lift trucks are generally used to load these vehicles. The visual tasks are to identify a shipping container or rack by part and destination and load it into the designated rail car or truck. (See Figure 24, color insert.) General lighting with adjustable or portable supplementary lighting will provide good vertical illuminance for the rail car or truck trailer interior.

15.3 Machining Metal Parts

While computer numerically controlled (CNC) machines do most precision work, much of the following information still applies, especially as pertaining to Set-up work. Machining of metal parts consists of the preparation and operation of machines such as lath- es, grinders (internal, external and surface), millers (universal and vertical), shapers and drill presses, bench work, and inspection of metal surfaces. The precision of such machine operations usually depends upon the accuracy of the setup and the careful use of the graduated feed-indicating dials rather than the observation of the cutting tool or its path. The work is usually checked by portable measuring instruments, and only in rare cases is a precision cut made to a scribed line. The fundamental visual task is to dis- criminate detail on planar or curved metallic surfaces.

General Lighting: Most of the visual tasks in the machining of metal parts are best lighted by large- area low-luminance sources. The ideal general lighting system would have a large indirect component. While both fluorescent and high-intensity discharge sources can be used for general lighting, fluorescent luminaries, particularly in a grid pattern, are sometimes preferred for low mounting heights. High-reflectance room surfaces improve illumination and visual performance.

Since workers often refer to information on CRT screens, the needs of this visual task must be considered. In particular this refers to veiling reflections on the CRT screen from luminaries, light surfaced walls, and windows.

16.0 LIGHTING FOR SPECIFIC VISUAL TASKS

This section describes certain industrial visual tasks and suggested lighting techniques for addressing them.

16.1 Convex Surfaces

Discriminating detail on a convex surface, as in reading a convex scale on a micrometer caliper, is a typical seeing task. The reflected image of a large-area low-luminance source on the scale provides excellent contrast between the dark figures and divisions and the bright background without producing reflected glare. The use of a near-point source for such applications results in a narrow, brilliant band that obscures the remainder of the scale because of the harsh specular reflection and loss of contrast between the figures or divisions and the background. (See Figure 25.)

Figure 25. (Left) Micrometer illuminated with a system of small, bright sources is seen with bright streak reflections against a dark background. (Right) When illuminated with a large-area, low-luminance source, the micrometer graduations are seen in excellent contrast against a luminous task background.

16.2 Flat Surfaces

In viewing a flat surface, such as a flat scale, the seeing task is similar to that in reading a convex scale. With a flat scale, however, it is possible, depending on the size, location and shape of the source, to reflect the image of the source either on the entire scale, or only on a small part of it. If the reflected image of the source is restricted to too small a part of the scale, the reflection is likely to be glaring.

16.3 Scribed Marks

The visibility of scribed marks depends upon the char-

40


acteristics of the surface, the orientation of the scribed mark and the nature of the light source. Directional light produces good visibility of scribed marks on untreated cold-rolled steel if the marks are ori- ented for maximum visibility, so that the brightness of the source is reflected from the side of the scribed mark to the observer’s eye. Unfortunately, this technique reduces the visibility of other scribed marks. Better results are obtained with a large-area low-luminance source. If the surface to be scribed is treated with a low-reflectance dye, the process of scribing will remove the dye and expose the surface of the metal. Such scribing appears bright against a dark background. The same tech-

Size source required

Eve n

\

\ \

Width of luminous area \\ \ \. \

“\ Figure 26. Procedure used for establishing the luminaire size necessary to obtain source reflections on a flat specular surface.

nique is appropriate for lighting specular or diffuse aluminum. In this case, the scribed marks will appear dark against a bright background.

16.4 Center-Punch Marks

A visual task quite similar to scribing is that of seeing center-punch marks. Maximum visibility is obtained when the side of the punch opposite the observer reflects the brightness of a light source. A directional source located between the observer and the task provides excellent results when the light is at an angle of about 45” with the horizontal.

16.5 Concave Specular Surfaces

The inspection of concave specular surfaces is difficult because of reflections from surrounding light sources. Large-area, low-luminance sources provide the best visibility. In the machining of small metal parts, a low-luminance source of approximately 1700 cd/m* is desirable. The size of the source depends on the shape of the machined surface and the area from which it is desired to reflect the brightness. The techniques applicable to specular reflections can also be applied to semispecular surfaces.

16.6 Flat Specular Surfaces

The geometry for determining luminous source size is illustrated in Figure 26. First, draw lines from the extremities of the surface that is to reflect the source, to the location of the observer’s eye, forming an angle a. At the intersections of these lines with the plane of the surface, erect vertical lines from that plane, forming angles b l and b2. Project these lines to the luminaire location to define the luminaire width; extend them in the opposite direction until they intersect, forming an angle.

16.7 Convex Specular Surfaces

The appropriate width of the luminous area of the convex surface is shown in Figure 27. Draw lines from the location of the observer’s eye to the edges of the surface’s luminous area, forming angle a. Erect normals at intersections of lines with the surface. At these intersections and on the other side of the normals, construct lines to form angles equal to those to the eye (the same procedure as that for flat surfaces described above). Project lines (as for flat surfaces) to define the luminaire width. This procedure can be applied to concave surfaces.

I Size source required

I I / I I / E?? position

Established ’ \ mounting \

\ ‘.( height

I

/..- Width of luminous area

8 = 2 u + a

Figure 27. Procedure used for establishing the luminaire size necessary to obtain source reflections on a convex specular surface. In the diagram, q = 2s + a.

41


16.8 Lighting and Visibility Issues for Specific Visual Tasks for Sheet Metal Fabrication

Visual tasks in the sheet metal shop are often difficult because sheet metal (after pickling and oiling) has a reflectance similar to the working surface of the machine, resulting in poor contrasts between the machine and work. Low reflectance of the metal results in a low task luminance. High-speed operation of small presses reduces the available time for seeing and bulky machinery obstructs the distribution of light from general-lighting luminaries. Noise also contributes to fatigue.

16.8.1 Punch Press

The seeing task is essentially the same for a large press as it is for a small press, except that with a small press less time is available for seeing. The shadow problem, however, is much greater with a large press. The operator must have adequate illuminance, often from supplementary or task lighting, to move the stock into the press, inspect the die for scrap after the operating cycle is completed and inspect the product. Where an automatic feed is employed, the speed of operation is so great that the operator has time only to inspect the die for scrap clearance.

The general lighting system in press areas should provide illuminance adequate for the safe and rapid handling of stock in the form of unprocessed metal, scrap or finished products. In large press areas illumination should be furnished by high-bay lighting equipment or by a combination of high-bay and supplementary task lighting. For moderate mounting heights, the illuminance should be supplied by luminaries having a widespread distribution to provide uniform illuminance for the bay and the die surface area.

The operator’s ability to inspect the die is more directly related to the reflected brightness of the die Surface than to the amount of light incident upon it. For example, a concentrated light placed on the operator’s side of the press and directed toward the die may produce results much less satisfactory than a large-area source of low luminance placed at the back or side of the press. The luminance required for optimum visibility of the die has not been established; consensus suggests that 1700 cam2 is satisfactory.

Paint applied to both the exterior and the throat surfaces of a press contributes to the operator’s ability to see. The reflectance of the paint selected for the exterior of the press should be not less than 40 percent. This treatment of vertical surfaces on the exterior provides for maximum utilization of light from the general lighting system. Similarly, the paint selected for throat surfaces should have a reflectance of 60 percent or higher.

16.8.2 Shear

The operator must be able to see a measuring scale in order to set the stops for gauging the size of cut. When a sheet has to be trimmed, either to square the sides or to cut off scrap from the edges, the operator must be able to see the location of the cut in order to minimize scrap;

The general lighting system should provide adequate illuminance in the area around the shear to safely feed the sheets at the front, collecting the scrap at the back and stacking the finished pieces in preparation for removal. Local lighting should indicate where the cut will be made and the amount of scrap that will be trimmed. It also provides light to enable the operator, who is responsible for pressing the foot-release bar, to see quickly that all hands are clear of the guard.

16.9 Lighting for Large Component Sub- and Final Assembly

This phase of manufacturing has special requirements not usually found in other industrial operations. Modern industrial requirements have necessitated the construction of buildings with clear bay areas, which may exceed 26,000 m2 (300,000 ft2) and truss heights of more than 24 m (80 ft) from floor level. The lighting problems in buildings of this size are not confined to the engineering and design concepts but include the task of maintenance and lamp replacement. The use of either a system of catwalks or traveling-bridge cranes may be appropriate to allow access to the lighting units. In some cases, mobile telescoping cranes can be used to reach luminaries from the floor, but the heights involved and obstructions on the floor may make this method of maintenance impractical. Where access is available from the floor, disconnecting hangers and lowering chains can be an effective method for maintaining luminaries in high-bay areas.

One special problem in lighting certain assembly tasks, is that the lighting is usually designed to specific task levels with the assumption that the areas will be completely open, whereas in reality that is seldom so. The lighting from overhead systems is often reduced by the presence of large assemblies or large production equipment. .

Typical of the types of assemblies found in these facilities are aircraft and automobile sub-assemblies and the installation of sub-systems in these assemblies for which supplementary lighting is often required.

Assembly of large aircraft sections, for instance, can present special lighting problems. Exterior lighting for joining together these sections requires both horizontal and vertical illuminance as well as lighting installed

42


in such a manner that it will light the underside of the body and wings. Use of floodlights can give both components of light on the exterior body and also provide light to the undersides of the body and wings. Specially mounted luminaries or portable lighting are required to light areas such as landing-gear pockets. High reflectance floor finishes will aid in lighting the underside of assemblies but supplementary lighting is still usually required. See Figure 28 (a) , (b) and (c).

Figure 28 (b) for aircraft assembly. (Photo courtesy of Holophane.)

Figure 28 (a) Light surfaces, including the floor, insure high quality lighting (a) for truck assembly. (Photo courtesy of Hubbell Lighting.)

16.10 Control Rooms

The control room is the nerve center of facilities such as electric generating plants, electric-dispatch facilities, steam or hot water generating plants, and chemical plants, and it must be continuously monitored. Lighting must be designed with special attention on the comfort of the operator; direct and reflected glare and veiling reflections must be minimized, and luminance ratios must be low. Along with ordinary office-type seeing tasks, the operator has to read gauges, meters and other monitoring devices, often at distances of 3-4.5 m (1 0-1 5 ft) away. Reflected glare and veiling reflections must be eliminated from these indicating devices, including those with curved glass faces.

While the practice is not standardized, most control-room lighting involves one of two general categories: diffuse lighting or directional lighting. Diffuse lighting may be from low-luminance, indirect lighting equipment, solid luminous plastic ceilings or louvered ceilings. Directional lighting may be from recessed troffers, which follow the general contour of the control board. (These luminaries must be accurately located to keep reflected light out of the glare zone.) Lighting for the rest of the room may be from any type of low-luminance general lighting equipment.

-- _I --I_---- ~ -

Figure 28 (c) for maintenance in a hangar. (Photo courtesy of Ruud Lighting.)

As control room data displays are more and more dig- ital, the problems concerning lighting and CRTs are more in evidence. Many operators like to have black or dark colored backgrounds on their CRTs in order to increase the contrast between pixel derived data’and its background. In this instance the veiling reflection problems are increased over those with light background panel meters. Under these conditions light surfaced walls behind the operator, walls and lighting outside of glass partitions, floors and even light reflecting off the operator’s clothing and the table sur-

43


faces next to the operator can show up as a veiling reflection in the CRT screen.

Often, the orientation and tilt angle of these CRT screens may not be easily adjusted to reduce objectionable screen reflections. In these cases, control of sources of direct and reflected light relative to the screens and operators is even more critical. (Figure 29, see color insert.)

16.11 Warehouse and Storage Area Lighting

Placing items in storage, accounting for them and later retrieving them are some of the most widespread activities requiring electric lighting in industrial facilities. Storage activities are found in business operations of every type, ranging from small local operations to multinational corporations.

Since rapid changes are taking place, the traditional concept of the warehouse must be expanded to encompass new techniques, including automation, high-rise storage, bar coding, cold storage, and shrink-wrap packaging .

16.11.1 Types of Warehouse Area and Storage Systems

A variety of warehouse areas and storage systems requiring specific tasks may occur in warehouse usage:

Open Storage. Areas of material stored without the use of rack systems. This includes storage on the floor and on pallets, which may be stacked on each other. In Figure 30 (see insert page IV) the center area of a production facility is used for storing aluminum coils.

High Rise. Areas generally automated, where storage bins may be rotated so that unused bins are kept high up, and with storage levels rising to over 30.5 m (1 O0 ft).

Fixed Racking. Areas with fixed racking may range from 1-4 m (3-12 ft) wide and from 2.5-9 m (8 to 30 ft) high. Items may be in bins, on racks, or in various types of containers. Labeling of the racks, containers or bins can vary from large black-on-white lettering to small, hard-to-read hand written labels.

Mobile Racking. A storage system now widely used in North America. Entire blocks of racking move on floor-mounted rails to open and close aisles as needed. In order to obtain maximum use from any lighting provided, the definition of the actual seeing task should be considered.

Off ices. Papetwork areas located within warehouses require lighting appropriate for office tasks.

Stockroom Area: Identification marks on the sides of bulky materials, rolls of paper, and crates or boxes require vertical illumination. Additional lighting should be provided over the aisles where high piles of stock interfere with general lighting.

Cold Storage. Areas that warehouse normally per- ishable food items and require low (sometimes below freezing) temperatures. See Section 10.5 on Low Ambient Temperatures.

Hazardous Materials Storage. Areas where hazardous gases, vapors, or dust are or could be present require specific methods of storage. Local building code requirements should be checked as to permissi- ble luminaries for lighting areas where hazardous materials are stored or used. See Section 10.5 on Classified Areas.

Exit and Emergency. Areas within warehouses that provide safe passage through to exit from the building and that must conform to Life Safety Codes in case of emergency.

Shipping and Receiving. Areas where materials are received into the warehouse for sorting and piace- ment in storage areas. Areas that setve as staging areas for coordination of products to be sorted and placed on trucks or trains to be shipped. One of the most difficult visual tasks is reading markings on ship- ments, labels and bills of lading. General illumination may provide sufficient light for these tasks and for the operation of manual or powered forklift trucks, as well as for general traffic in the area.

Supplementary lighting may be necessary for the interi- or of transport carriers bringing material to the plant. Angle or projector-type luminaries may be utilized, but care must be taken to avoid glare from these sources. If the conveyances are deep, reel-type or other portable lighting equipment may be necessary. Yard or loading-dock lighting should be installed for night operation.

Loading Docks and Staging Areas. Areas, generally just outside the shipping area, that may be outdoors but are often covered and that are used to place items on and off trucks and railroad cars and to assemble goods.

Maintenance Shops, Fork Lift Recharging Areas and Refrigeration Equipment Rooms. Locations where general plant housekeeping activities occur. Separate areas or rooms are generally set aside for these purposes.

16.11.2 Warehouse Illuminance3

Vertical illuminance. From the tasks encountered in the warehouse, it can be concluded that the majority

44


of critical seeing tasks occur in a vertical plane. A major consideration, therefore, in warehouse lighting design is providing illuminance on the vertical surfaces of stored goods. Illuminance should be distributed uniformly over the entire vertical seeing surface, from top to bottom, and along the entire length of storage aisles. (See Figure 31 .)

Figure 31. Warehouse with uniform distribution along the length of the storage aisle. (Photo courtesy of Holophane.)

The reflectances of exposed surfaces can significantly affect lighting results. While the reflecting characteristics of stored goods cannot be controlled at the warehouse operating level, they should be taken into consideration when carton and container decisions are being made. Light-colored packing material can contribute to efficient utilization of available light and increase visibility through greater contrast. Clear plastic wrappings over packages can reduce visibility of labels and markings due to reflected glare from the plastic wrap.

Some racks and storage locations may be partly or wholly empty at times. The lack of reflecting surfaces in the empty shelves may reduce the overall illuminance. This effect should be anticipated and included in the design parameters.

Horizontal illuminance. While not as critical as the need for vertical illuminance, adequate horizontal illuminance must be provided for safety and navigation in the aisles. Other horizontal-plane tasks include reading of documents such as pick tickets.

Recommended illuminance levels for warehouses are shown in Figure l(a).

16.11.3 Warehouse Lighting Design Considerations

Since storage in fixed-location racking generally results in long narrow aisles, lighting layout and calculation procedures should be based on the dimensions of the aisle space rather then the overall building size parameters. Lighting fixtures should be located over the aisles (generally in the middle), regardless of the overall building configuration. Because of the special geometry of aisle space, which generally yields cavity ratios higher than 10.0, and because the determination of vertical illuminance is a key task, the Lumen Method of average illuminance calculation (see Annex C) is not effective for such warehouse calculations. Computer programs for point-by-point calculation of both horizontal and vertical illuminance, now generally available throughout the industry, are much more effective calculation tools.

To help ensure a productive work environment, glare from light sources should be minimized. This becomes particularly important when concentrated HID sources are used because operators working beneath luminaries may encounter disability glare when looking up to the top of stacks. Proper shielding of the source needs to be considered, as well as viewing angles up and along the aisles.

Indirect lighting systems for warehouses, while not as efficient in producing illuminance, can be useful in providing excellent seeing results and have proved particularly useful in areas with computer terminals and where both storage and selling take place. Ceiling surfaces with high reflectance characteristics are important when considering indirect lighting systems.

Aisles or narrow “rooms” can be lighted with HID sources in classical high-bay luminaries, provided that the luminaries are spaced reasonably close together to avoid unacceptable drop-off of illuminance between luminaries. The spacing can be increased with luminaries that have a substantial uplight component when the ceilings have high reflectance. Other equipment choices include low-bay luminaries or special aisle luminaries that have an asymmetric light distribution. HID sources in appropriate luminaries are generally most effective at mounting heights of 5 m (15 ft) or more. Special care must be taken at higher mounting heights to ensure that sufficient illuminance is produced along the entire height and length of the aisle stacks, especially when wider luminaire spacings are used.

Fluorescent lighting is frequently used for warehouse aisles and can be used effectively in mounting heights up to about 1 O meters (30 ft). Fluorescent designs are

45


implemented either with continuous rows along an aisle (in reflector, lensed, open strip types) or with individually mounted units.

Warehouse spaces are often accessed only intermit- tently. It is therefore possible to save energy by controlling light output with passive infra-red sensors or other control devices. Lamps are switched off or operated at reduced output at inactive times and then operated at full output only when the space is in use, or, in the case of a passive infra-red sensing system, when a person is present. Multilevel fluorescent and HID ballasts have been developed for this purpose. These lamps are operated at reduced levels when there is no activity, and a sensor activates the circuit when someone is present in the space. Significant energy savings can be realized, depending on the occupancy patterns of the space.

17.0 OUTDOOR AREA LIGHTING

Two different systems of lighting are commonly used to illuminate large, outdoor areas of industrial facilities: projected (long-throw) lighting and distributed lighting. Each has its advantages under specific situations.

17.1 Projected Lighting System

The function of this system is to provide illumination from a minimum of locations throughout the various outdoor work areas. This is usually accomplished by use of aimable floodlighting luminaries. (Figure 32, see color insert.)

Advantages are:

1. The use of high poles on towers reduces the number of mounting sites.

2. The light distribution is flexible. Both general and local lighting are readily achieved. (Aiming of floodlights, however, may be more critical.)

3. Floodlights are effective over long ranges. 4. Lighting system maintenance is restricted to a few

5. Physical and visual obstructions are minimized. 6. The electrical distribution system serves a small

concentrated areas.

number of concentrated loads.

Typically wide beam floodlights such as NEMA 5 through NEMA 7 distributions are not used to cover areas wider than two mounting heights in front (transverse dimension) of their locations. Individual floodlights should not cover more than 90 degrees in the horizontal plane. This means that at least two luminaries are needed when the location is at the side of an area. Four are needed for locations in the center of an area.

When coverage is more than two mounting heights transversely, narrower distributions, such as NEMA 2 and NEMA 3 are called for.

Coverage greater than four mounting heights from a location is not recommended. The use of projected lighting has a greater potential for direct glare and obtrusive light than distributed lighting.

Projected outdoor area lighting has the fewest locations and thus requires the least amount of aria1 structure. Structures are usually the most expensive part of the lighting system.

17.2 Distributed Lighting System

Distributed lighting differs from projected lighting in that luminaries are installed at many locations.

Advantages are:

1. Good illuminance uniformity on the horizontal

2. Glare can be controlled with the proper selection of cut-off luminaries 3. Good utilization of light (less wasted spill light) 4. Reduction of undesirable shadows 5. Less critical aiming 6. Lower mounting heights (floodlight maintenance is

7. Reduced losses to atmospheric absorption and

8. The electrical distribution system serves a large

plane

facilitated)

scatte ring

number of small, distributed loads

In the Distributed Lighting method, wall mounted equipment is often used at personnel and loading dock doors. Wall mounted equipment, however, should rarely be used to cover a transverse dimension greater than two mounting heights and a longitudinal (horizontal, to the side) area more than 4 mounting heights. This would place continuous area lighting equipment on 4 mounting height spacing along a wall.

Distributed outdoor area lighting systems have the least amount of glare because mounting heights can be lower. When floodlights are used, aiming angles can be less oblique, thus permitting glare control media such as louvers and visors to work. Care should be taken to keep aiming angles below 65 degrees above nadir.

17.3 Outdoor Tower Platforms, Stairways, and Ladders

Luminaries should provide uniform illumination and be shielded from direct view of persons using these structures. Enclosed and gasketed or weatherproof

46


luminaries equipped with refractors or clear, gasketed lenses may be used for reading gauges. Luminaries above top platforms or ladder tops should be equipped with refractors or reflectors. Reflectors may be omitted on intermediate platforms around towers so that the sides of the towers will receive some illumination and the reflected light will mitigate deep shadows. If luminaries are attached to equipment, care should be taken in mounting the luminaries to reduce damage from equipment vibration.

Normal installations have intense HID sources located fairly close to personnel. Exchanging coated for clear lamps may reduce glare in these situations, but may also significantly change the light distribution from luminaries.

17.4 Special Equipment

Special lighting equipment may be needed for such functions as illuminating the insides of filters or other equipment whose operation must be inspected through observation ports. If the equipment does not include built-in luminaries, concentrating-type reflector luminaries should be mounted at ports in the equipment housing.

Portable luminaries are utilized where access holes are provided for inside cleaning and maintenance of tanks and towers. Explosion-proof types (where hazardous conditions may exist) with portable cables are connected to industrial receptacles (either explosion-proof or standard as may be appropriate for the atmospheric conditions present) located near tower access holes or at other locations.

17.5 Low Illuminance and Visual Acuity Outdoors

In outdoor environments with low illuminance levels, the human eye’s processes of visual adaptation operate in three categories of vision: Photopic, Scotopic and Mesopic.

Photopic Vision is the human eye’s response at high light levels where the cones in the eye account for the majority of vision. This vision is generally associated with adaptation to a luminance of 2 3 cdm‘ (2 0.3 c w ) .

Scotopic Vision is the human eye’s response at very low light levels such as moonlight where the rods in the eye account for the majority of vision. This vision is generally associated with adaptation to a luminance of f 0.001 cd/m2 (f 0.0001 cd/ít2). Scotopic vision is largely irrelevant to most lighting design practice.

contribute to the visual response. This vision is generally associated with adaptation to a luminance between 3 and 0.001 cd/m2 (0.3 and 0.0001 cd/ft2). Low illuminance design should take into account the prevalence of mesopic conditions.

When clarity, depth of field, and peripheral detection are important, then a light source rich in short wave- length (blue and green) light should be used. Current research4 indicates that less light is required with a light source rich in green and blue components (metal halide, fluorescent) relative to a light source with few blue green and blue components, for an equivalent mesopic response.

Sources of different spectral composition that affect the eye equally at 3 cd/m2 (0.03 cd/ft2) and above may not affect the eye equally when those same sources are used at lower adaptation levels. This includes color matching, off-axis reaction time, and brightness perception. The spectral sensitivity of the eye and the effects of the spectral composition of light sources on brightness perception should not be confused with color rendering tasks or with color naming.5t6

References Rea, M., Editor, IESNA Lighting Handbook, 9th Edition, 2000. New York: Illuminating Engineering Society of North America.

IESNA. Lighting Economics Committee. 1996. Recommended Practice for the Economic Analysis of Lighting, IESNNRP-31-96. New York: Illuminating Engineering Society of North America.

IESNA. Industrial Lighting Committee. 1992. Design Guide on Warehouse Lighting. IESNNDG-2-92. New York: Illuminating Engineering Society of North America.

McGowan, T. and Rea. M. S., 1995. Visibility and spectral composition: Another look in the mesopic. 70 Years of CIE Photometv. Vienna: Commission Internationale de 1”Eclairage.

“Vision at Low Light Levels” Symposium, May 1998, Electric Power Research Institute, Lighting Research Off ice.

Rea, M. S., Essay by Invitation, Lighting Design and Application, Vol. 26 No.10 p.15. New York: Illuminating Engineering Society of North America, October, 1996.

Mesopic Vision occurs under the majority of exterior night lighting conditions and is a combination of photopic and scotopic vision. Both the rods and cones

47


(This Annex is not part of the American National Standard and Practice ANSIAESNA RP-7-2001.)

~ ~~ ~~

ANNEX Al THE BASIS FOR DEVIATING FROM RECOMMENDED ILLUMINANCES

Occasionally the visual task in a specific space is not typical and Figures Al .1 and Al .2 should be used to adjust the illuminance for that task. It is extremely important that the lighting designer have a clear understanding of the visual task being illuminated and then determine if the recommended illuminance is appropriate. It is also possible that more than one visual task is performed in a space. The designer should make provision to illuminate these tasks to the recommended levels unless other design criteria supercede illuminance as the design criterion.

A dramatic difference between an actual and a recommended illuminance (a difference of two standard devi-

Figure A l .1 Determination of visual task parameters.

ations or more) would be 'x more or 'x less than the recommended value. Such dramatic deviations should be carefully documented by the designer as part of good professional practice and for future reference.

The recommendations ' for illuminance in this Recommended Practice are not made with respect to the age of the occupants. Generally the visual requirements of older persons are significantly different from those of younger persons in two ways:

There is a thickening of the yellow crystalline lens, which decreases the amount of light reaching the retina, increases scatter within the eye, and reduces the range of distances that can be properly focused (presbyopia)

There is a reduction in pupil size, decreasing the amount of light reaching the retina.

The retinal illuminance of a 60-year-old person is only about one-third of the retinal illuminance of a typical

~~ ~~~~

CONTRAST How to calculate: IL, - Li/Lb or Ipb - ptl/p, where L is luminance (L,, and L, must use same units)

and p is reflectance b refers to the background t refers to the target

Definition of contrast using reflectance requires equal illuminance on task and background.

How to interpret: low contrast: 0.3 or lower, but not near threshold* high contrast: above 0.3 This division is based on the plateau-escarpment nature of visual performance 1.2

Target

SIZE (see also Figure Al -2) How to calculate: solid angle (sr): (d' cos8)/l?

where d, 8 and I are defined as for visual angle

where d is the dimension (length or width) of the critical detail of the target 8 is the viewing angle I is the viewing distance (d and I are in the same units)

visual angle: arctan(d cosû)/l

Note that only one dimension, d, is defined for the critical detail of the target. Visual performance for two different targets subtending the same area will be the same, even if the targets have different aspect ratios, e.g., a square- shaped target versus a long, rectangular-shaped object1,

4%


How to interpret: small size: 4.0 x lo6 sr or smaller (solid angle), but not near the acuity limit* large size: larger than 4.0 x

Note: 1" = 0.01 75 radians = 60 minarc; 1 sr = 66" visual angle for a circular target. For a cone where 9 is the half-cone angle, solid angle = 2n(1 - cosq).

This division, like that of contrast, is based upon the plateau-escarpment of visual performance.l.*

sr

*It should be noted that contrast threshold and the acuity limit are dependent upon background luminance, duration of presentation, color, surround conditions, and in general, any number of factors that affect visibility, including those idiosyncratic to the viewer. Above a contrast of 0.3 and a size of 4.0 x 1 O* sr, these factors are not very ¡important to visual performance.

Figure A1-2. Examples of common visual angles and solid angles.

Printed reading task from 15 in. (40 cm) Typeface size 6 point 8 point 10 point 12 point 14 point 24 point 36 point

Visual angle (")* 0.03 0.04 0.05 0.06 0.07 0.12 0.18

Solid angle (sr)f 1.7 x lo6 3.1 x lo6 4.8 x l o 6 6.9 x 9.4 x 10-6 2.8 x 10-5 6.2 x 10-5

*Angular width of single character stroke (vertical stroke, Times typeface). +Average solid angle of total printed area of character for numerical digits (see reference 1).

Viewing a square-shaped object from 100 ft (30 m) Object size Visual angle (") Solid angle (sr) 3 x 3 in. (7.5 x 7.5 cm) 0.14

0.57

6.3 x lo6

1.0 x 10" 6 x 6 in. (15 x 15 cm) 12 x 12 in. (30 x 30 cm)

0.29 2.5 x 10-5

Wire sizes (diameter in cross section) viewed from 15 in. (40 cm) Wire size Visual angle (") Solid angle (sr) American Wire Gauge (AWG) 30

AWG 24 (0.51 mm diameter) 0.07 1.6 x lo6 AWG 20 (0.81 mm diameter) 0.12 4.1 x lo6

(0.25 mm diameter) 0.04 3.9 x 1 0 7

AWG 16 (1.29 mm diameter) 0.18 1.0 x 105 AWG 12 (2.05 mm diameter) 0.29 3.3 x 10-5 AWG 8 (3.28 mm diameter) 0.47 6.7 x 10-5

Circular drilled holes viewed from 15 in. (40 cm) Hole diameter Visual angle (") Solid angle (sr)

0.02 in. (0.51 mm) 0.07 1.4 x lo6 0.03 in. (0.76 mm) 0.11 3.1 x lo6 0.04 in. (1 .O2 mm) 0.15 5.6 x lo6

0.01 in. (0.25 mm) 0.04 3.5 x 107

49


20-year-old person due to smaller pupil sizes and thicker lenses. (See Figure A l .3.) Additionally the near point of a typical 20-year-old person is 10 cm (4 in.), compared to more than 1 m (3 ft) for a typical 60- year-old person. (See Figure A l .4.)

References

Rea, M.S. and Ouellette, M.J. 1991. “Relative visual performance: A basis for application.” Lighting Research and,Techno/ogy. 23(3):135-144.

Rea, M.S. and Ouellette, M.J. 1988. “Visual performance using reaction times.” Lighting Research and Techno/ogy. 20(4):139-53.

Age in years

Figure Al .3 An estimate of‘ relative decline in retinal illuminance with age.

16

14

12

10

6

4

2

O 10 20 30 40 50 60 70

Age in years

Figure Al .4 l h e decrease of amplitude of accommo- dation with age.

50

Consequently, older persons tend to require higher task illuminances for the same retinal illuminance and because of reduced clarity in the lens, have reduced image quality. Similarly, greater attention to sources of glare within the field of view is more important for older than for younger persons for reasons of increased light scatter within the aged eye.


(This Annex is not pari of the American National Standard and Practice ANSVIESNA ßP-7-2001.)

ANNEX A2 RECOMMENDED ILLUMINANCE VALUES (TARGET MAINTAINED) FOR INDUSTRIAL LIGHTING DESIGN

Figure A2-1 Recommended Illuminance Values for Industrial Areas/Activitiec - Interior

51


52


Explosives manufacturing Hand h a c e s , boiling tanks, stationary driers, stationary and gravity crystallizers Mechanical furnace, generators and stills, mechanisai dners, evaporators, filtration,

ater treatinu areA

300 (30) 300 (30)


54


55


56


Fabric dyeing (printing) 300 (30)

Drying, stripping 300 (30) Grading and sorting lSOO(150) ,

Upholstering 1500 (150)

Tobacco products

a Industry representatives have established this table of single illuminance values. Illuminance values for specific operations can also be determined by using illuminance values for similar tasks and activities.

Color temperature of the light source is important for color matching.

Special lighting such that (i) the luminous area is large enough to cover the surface which is being inspected and (2) the luminance is within the limits necessaq to obtain comfortable contrast conditions. This involves the use of sources of large area and relatively low luminance in which the source luminance is the principal factor rather than the illuminance produced at a given point.

Maximum levels - controlled system.

e Higher levels from local lighting may be required for manually operated cutting machines.

If color matching is critical, use illuminance of 3000 lx (300 fc).

Supplementary lighting should be provided in this space to produce the higher levels required for specific

f

seeing tasks involved.

Additional lighting needs to be provided for maintenance only.

57


, Hump area (vertical) 200 (20) 100 (10) Control tower and retarder area (vertical)

Body 10 (i) Head end 50 (5)

58


Ways Fabrication areas

Active Inactive

Storage yards

100 (IO) 300 (30)

50 (5)c 10 (1)

Select upper level for high speed conveyor systems. For grading redwood lumber 3000 lux (30 fc) is required.

Supplementary lighting may be required in some cases.

59


Figure A2-3 Recommended Illuminance Values (maintained on the task) for Specific Industries

60


Indoors Paper mP - preparation Groundwood mill grinder room Beater room Brown stock washers

700 (70) 300 (30) 500 (50)

61


62


a Obtained with a combination of general lighting plus specialized supplementary' lighting. Care should be taken to keep within the recommended luminance ratios (see Figure 2 in RP-7). These seeing tasks generally involve the discrimination of fine detail for long periods of time and under conditions of poor contrast. The design and installation of the combination system much not only provide a sufficient amount of light, but also the proper direction of light, diffusion, color and eye protection. As far as possible it should eliminate direct and reflected glare as well as objectionable shadows.

' The specular surface of the material may necessitate special consideration in selection and placement of lighting equipment, or orientation of work.

These illuminances are not intended to be mandatory but are recommended practice to be considered in the design of new facilities. For minimum levels for safety, see section 14.2 and Figure 15 in RP-7. All illuminances are average maintained levels.

indicates vertical illuminance.

Refer to local governing body for lighting requirements.

The use of many areas in petroleum and chemical plants is often different h m what the designation may infer. Generally, the areas are small, occupancy low (restricted to plant personnel), occupancy infrequent, and only by personnel trained to conduct themselves safely under unusual conditions. For these reasons, illuminances may be different from those recommended for other industries, commercial areas, educational facilities or public spaces.

Refer to FAA regulations for required navigational and obstruction lighting marking.

Localized general lighting.

' Obtained with a combination of general lighting plus supplementary lighting. Care should be taken to keep withiin the recommended luminance ratios. ** Maximum levels - controlled system.

63


(This Annex is not part of the American National Standard and Practice ANSVIESNA RP-7-2007.)

ANNEX B PREDICTIVE METHODS FOR DETERMINING

VISUAL COMFORT PROBABILITY (VCP) AND UNIFIED GLARE RATING (UGR)

One of the important factors in designing a lighting system for an Industrial Facility - or any space - is glare control. This will have an impact on the perception of comfort within the space and the degree to which the lighting system design is considered successful. Usually, we think of “glare” as something to be avoided in the design of a lighting system because it creates discomfort, disability or both, for the observer. There are, of course, situations in which glare is intentionally introduced. Examples include glare from a security lighting system, which limits the visibility of conditions within a secured facility or glare produced by moveable lighting equipment in theatrical períor- mances.

When glare is to be avoided, there should be some means of predicting, during the design phase of a project, what the effect of glare from the lighting system will be BEFORE the lighting equipment is installed. There have been attempts over the past forty years to develop systems that will predict the effect of glare on the observer. One system for predicting glare, developed in North America, is Visual Comfort Probability (VCP). In European countries, there have been several systems over the last 20 to 30 years. In an attempt to rationalize these various systems, the Commission Internationale de I’Eclairage (CIE), in 1995, proposed the Unified Glare Rating (UGR) system, which tries to incorporate the best features of the various European national glare prediction methods into one universal system.

At the present time, VCP and UGR seem to be the world’s two most accepted glare prediction systems. If UGR is to become the world standard in this area, it is in our best interests to understand the system.

A brief description of each of these two systems follows to introduce the concepts, and limitations, of each. The calculations used in predicting accep- tance of a lighting system in each of the systems are included for information only since the information can be made available by the manufacturers of lighting equipment as a single rating number where it is relevant to the applications. For those who may wish to investigate this subject in more depth, the documents included in the References will be a good place to start.

Visual Comfort Probability (VCP)

The Visual Comfort Probability system for evaluating glare from a lighting system was developed in the United States in the 1960’s. The system was derived by combining the photometrics of the luminaries test- ed and the size of various rooms with the discomfort glare evaluations from a set of observations made by average viewers. From a large data base of observations by test subjects, a series of formulae were generated which could, with acceptable accuracy, repro- duce the experimental results and calculate a VCP value for a given luminaire. The VCP number determined from the calculations is intended to represent the number of people, out of a total number of 100 (therefore, it becomes a percentage of the total), who would consider the lighting system in the room to be Comfortable from the standpoint of glare. It has been concluded from experimental data that a difference in VCP of five points or less is insignificant. Figure B-1 shows a typical set of VCP values.

Figure B-i. An example of a table of VCP values.

Room Luminaires Lengthwise Luminaires Crosswise

W L 8.5 10.0 13.0 16.0 8.5 10.0 13.0 16.0

20 20 78 82 20 30 73 76 20 40 71 73 20 60 69 71 30 20 78 82 30 30 73 75 30 40 70 72 30 60 68 69 30 80 67 69

40 20 79 82 40 30 74 76 40 40 71 72 40 60 68 69 40 80 67 68 40 100 67 68

60 30 75 76 60 40 71 72 60 60 69 69 60 80 68 68 60 100 67 67

100 40 74 75 100 60 71 71 100 80 70 70 100 100 69 68

90 82 78 74 88 80 75 71 69

87 79 74 70 68 67

79 74 69 67 66

75 71 68 66

94 77 81 88 72 75 82 70 72 78 68 70 92 77 81 85 72 74 78 69 71 74 67 69 72 67 68

92 79 82 84 73 75 77 70 71 72 68 69 70 67 68 69 67 67

83 74 76 76 71 72 71 68 69 69 67 68 67 67 67

78 74 74 72 71 71 69 70 69 67 69 68

89 81 76 73 87 79 74 70 68

87 78 73 69 67 66

78 73 68 66 65

75 70 67 66

93 86 80 76 92 84 77 73 71

91 83 76 71 69 68

82 76 70 68 66

77 72 69 67

This example is for use when the units of length and illuminance are the foot (ft) and footcandle (fc). VCP values are identical if units of length and illuminance are the meter (m) and the lux (lx).

Wall Reflectance, 50%; Effective Ceiling Cavity Reflectance, 80%; Effective Floor Cavity Reflectance, 20%; Luminaire No. 000; Workplane Illuminance, 100 fc

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In order to allow for a comparison of several types of luminaries in different types of room configurations, a set of criteria was developed and these criteria are the only ones for which experimental data are available and, therefore, the only ones for which it can be said, with any certainty, that the VCP evaluation system works. The standard conditions adopted for VCP calculations are:

The initial illuminance shall be 1 O00 Ix (1 O0 fc) Room surface reflectances shall be:

ceiling cavity 80%

floor cavity 20% walls 50%

Mounting heights above the floor: 2.6; 3; 4; and 4.9 m (8.5; 1 O; 13 and 16 ft.) A range of room dimensions to include square, long narrow and short wide rooms A standard layout involving luminaries uniformly distributed throughout the room An observation point 1.2 m (4 ft) from the rear wall of the room and 1.2 m (4 ft) above the floor A horizontal line-of-sight directly forward A vertical limit to the field of view corresponding to an angle of 53” above, and directly forward from, the observer.

The system was validated using lensed, direct distribution, flat bottom fluorescent luminaries only. For this reason, it should not be used with small source incandescent or fluorescent, suspended HID, indirect or luminous ceiling lighting systems.

By consensus, discomfort glare will not be a problem when all of the following conditions are met by the lighting system:

The VCP is 70 or more; The ratio of maximum luminance (luminance of the brightest 6.5-cm2 [ l -in2]) to the average luminaire luminance does not exceed 5:l at vertical angles of 45, 55,65,75 and 85” above a vertical line (nadir) through the luminaire in both the cross-wise and the lengthwise directions; The maximum luminances of the luminaire, in both the cross-wise and length-wise directions, does not exceed the following values:

VERTICAL ANGLE MAXIM UM ABOVE NADIR LUMINANCE

(degrees) (cd/m2) - 45 55 65 75 a5

771 O 5500 3860 2570 1695

Unified glare Rating (UGR)

In 1995, the Commission Internationale de I’Eclairage (CIE) published a document with its proposed glare rating system, the Unified Glare Rating (UGR). The system was developed from a document published earlier by CIE, Publication #55, in which a Glare Index Formula was introduced. This formula was based on a study of the then current research and practice. There has been some difficulty in making this system work based on the calculation procedure that was included in CIE Publication #55. Therefore, the process has been somewhat simplified, primarily by the omission of reference to vertical illuminance at the observers eye.

All of the formulae used by European members of CIE for a glare rating technique follow roughly the same form:

Formula 1

where:

C, = a constant determined experimentally C, = a constant determined experimentally fm,, = background luminance of the room flurninaire = luminance of a luminaire

As is the case with VCP, the lighting related factors which are prominent in the UGR formula are background luminance, average luminance of the luminaries (light sources), the solid angle subtended by each of the individual luminaries from the observer’s eye and the Guth Position Index. All of these factors are calculated the same way for either the VCP or the UGR methods with the exception of background luminance. The UGR method uses background luminance of the room surfaces within the field of view, excluding the luminaries, while average luminance of the total field of view, including luminaries, is used in the VCP calculation. This may be seen later in the calculations. In addition, the luminaire and observer positions are determined in a manner very similar to the VCP method.2

CIE believes that the current Unified Glare Rating formula contains the best parts of the various systems recently used in the European countries to predict discomfort glare. The scale of the system is an “interval scale” where the difference between the numbers are glare differences which can be seen by an observer. Therefore, in the UGR method, a difference of one number on the scale is significant. The scale used to indicate the level of glare determined by these formulae is the same as the scale used in the British system

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for nearly 30 years. It has been found acceptable and there seemed to be no reason to change a working model. The practical range of the UGR scale is between 10 and 30. Unlike the North American VCP scale, a lower number on the UGR scale indicates a system with less glare. (See Figure B-2.)

RATING VALUE SUGGESTED UGR

Just Intolerable 31 Uncomfortable 28 Just Uncomfortable 25 Unacceptable 22 Just Acceptable 19

Imperceptible 10 Perceptible 16

Figure B-2. Categories of discomfort glare and equivalent UGR values from Akashi, et al?

Ageneral means of interpreting this scale has been suggested using research performed in Japan (see Figure B-2). Generally speaking, it is felt the range of acceptable glare ratings for the UGR system is between 10 and 20 for offices with the lower numbers being more acceptable. Figure B-2 indicates glare ratings of 1 O are imperceptible while glare ratings of 22 are unacceptable. A UGR number of 20 has been determined to be the limiting glare value for offices. The results of these experiments suggest the number of luminaries in the field of view may influence the ratings. Researchers also found that untrained observers seemed to rate lighting systems as being more glaring than trained lighting observers. That is, they tended to assign higher UGR number and lower VCP numbers. It should be noted that other researchers have questioned the interpreta- tion of the observations reported by Akashi, et a1.3

There are some limitations to the UGR system, as there are to the VCP system. At this time, it is not known whether the UGR system will work satisfacto- rily for luminous ceiling or indirect lighting systems. More research is needed in these areas. The data used to validate the UGR system was limited, much as was the VCP research, to sources which have a maximum solid angle at the observers eye of 0.1 steradian (a source of about 1 m2 viewed from a distance of 3 m)‘. In addition, the UGR system should not be used for the present, at least, for sources smaller than the equivalent of an incandescent downlight.

Which System is Better?

At this time, it may be too early to tell. There are limitations to both systems. The scales produced by the two systems are opposed to each other. A high number in the VCP system indicates low glare while a low number in the UGR scale indicates less glare.

66

Is there a correlation between the two systems? There could be. The glare sensitivity of any given individual is vague, at best. This is borne out by the large standard deviations and the poor reproducibility of the glare observations within any group.4 At least one study has been performed which compared calculations of VCP and UGR for five lighting situations. The result is indicated in Figure 8-3 and shows that a curve can be generated to relate VCP to UGR. The dotted lines on the graph indicate one set of common points in the calculations for both VCP and UGR. As can be seen, a VCP value of 70 translates to a UGR value of 19. This was the case for each of the five calculations made for this study and the curve shown on the drawing is the result of those calculations. Studies have indicated that UGR has a reasonable record of success in predicting the sensation of glare.

VCP

Figure 8-3. The relationship between VCP and the UGR,discomfort glare

More work is required before a correlation between the two systems can be formalized.

VCP calculation^:^

To calculate VCP, several intermediate calculations must be made. It is necessary to determine the position index and the average luminance of each luminaire, the function Q, which is determined from the solid angle of each of the luminaries at the position of the observer, and an index of sensation M. The Discomfort Glare Rating (DGR) is then determined from a summation of all of the values of M. Finally, the VCP will be.determined using the DGR. It is fairly obvious that this is not a calculation to be entered into casually. The various formulae are listed here only for information.

The Position Index is a value, P, determined for each luminaire by the following formula. It is a means of weighting each of the luminaries in the field of view to account for the fact that not all luminaries will impact the observer in the same way. As the luminaire is moved further from the line of sight, the impact upon the observer’s impression of glare is reduced.

ANSI / IESNA RP-7-01 -

Formula 2 (See Figure 8-5 for a description of o.)

P = exp[(35.2-0.31889a-1.22e-~" 9)1~-3

ß +(21+ 0.26667a - 0.002963a2)1O-'ß2] where: a = angle from a vertical line directly ahead of the viewer's line of sight and a line from the observer to the luminaire in a plane perpendicular to the luminaire. (See Figure 8-4.) p = angle between the line of sight at the observer and a line to the luminaire center from the observer.

Observer

Figure B-4 Geometry defining position index as used in VCP and UGR methods.

This data is also available in the form of a table, which would be, obviously, a much easier way to obtain these values.

The average luminance for the entire field of view is found from the following Formula: Formula 3 where:

1, = average luminance of the walls (cd/m2) L, = average luminance of the floor (cd/m2)

Lwww + L , W , + L'W' + c L, 0 , 1 4 F, =

5 L, = average luminance of the ceiling (cd/m2) L, = average luminance of the source (cd/m2) o,= solid angle subtended at the observer by the walls (in steradians) of = solid angle subtended at the observer by the floor (in steradians) o, = solid angle subtended at the observer by the ceiling (in steradians) o, = solid angle subtended at the observer by the source (in steradians) n = the number of the source being calculated (from n=l to n=n).

Figure B-5 Solid angle oabcdefg visible from the observer's location includes the bottom surface, one end and one side surface of the drop diffuser on the fluorescent luminaire.

The average luminance in this formula, F,, is called L, in some other formulae, including the UGR formula, which follows later in this Annex.

A function Q has been developed which is used in the calculation of VCP:

Formula 4

Q = 20.40,, + 1.520:'~ - 0.075 where: o, = the solid angle subtended at the observer by the source (in steradians). The solid angle is equal to the area of the luminaire (source) in m2 (ft2) divided by the square of the distance from the observers eye to the center of the luminaire (source) in m2 (ft').

After making these calculations, the values of P, F, and Q are used to calculate the Index of Sensation, M for each of the luminaries in the field of view:

Formula 5

0.50L,vQ P,,Fv".44

M , =

where Ls is the average luminance of the source (or luminaire) being calculated in the direction of the observer. The factor 0.50 in the numerator of the pre- ceding Formula allows for the use of the units indicated in these calculations.

From the above information, a Discomfort Glare Rating (DGR) can be calculated using the following:

Formula 6

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where: Formula 10* n = the number of luminaries in the field of view M, = index of sensation for the ‘7th” source (with the last source being equal to “n”).

The calculation for the summation (C) of all of the “Indices of Sensation” (M,) requires a separate calculation for the Index of Sensation for each of the luminaries in the field of view.

Finally, we are ready to make the calculation of VCP using the following formula:

Formula 7

VCP = - e

UGR Calculations’:

As will be remembered, the background luminance in the VCP calculation is the value F, and it includes the luminance of each of the luminaries. In the UGR formula, the background luminance of the space is determined by the formula:

Formula 8

*There are many forms of this formula in print today. This one has been selected for use here because it seems to speak with the most authority for the CIE.

References:

I. CIE Publication # I 17-1 995., 1995, Discomfort Glare in Interior Lighting, Vienna, Austria:CIE

2. van Bommel, Ir. W.J.M, A new international system for glare evaluation for interior lighting.

3. Mistrick, R., and Choi, A-S., A Comparison of the Visual Comfort Probability and Unified Glare Rating Systems, J. of the /ES 28 (no2) 94-101

4. Einhorn, H., Unified glare rating (UGR): Merits and application to multiple sources, CIBSE, London, Lighting Research and Technology, 1998

5. IESNA, 2000, IESNA Lighting Handbook, 9lh Edition, Chap 3, New York, NY

L -1 E ?T

6. 1991, 1 st International Symposium on Glare, Symposium Proceedings, Lighting Research Off ice (formerly Lighting Research Institute), Electric Power Research Institute, Palo Alto, CA.

h -

where E, is the indirect illuminance at the eye of the observer.

In the CIE method for UGR, Ei may be determined in several ways, but a simplified approach is to assume the indirect illuminance (E,) at the observer’s eye will be equal to the indirect illuminance on the walls of the room. This method seems to work well for general lighting systems with a uniform layout of luminaries. It is unclear whether this will be true for non-uniform luminaire layouts.

The calculation of the luminaire luminance divides the average luminous intensity in the direction of the observer’s eye by the area of the luminaire, A,:

Formula 9

Using these calculations, the values for and the Guth Position Index P as determined earlier, the UGR may be calculated by use of the formula:

68


(This Annex is not part of the American National Standard and Practice ANSI/IESNA RP-7-01.)

ANNEX C AVERAGE ILLUMINANCE CALCULATION: THE

LUMEN METHOD

Choosing a Calculation Method

Lighting calculations are performed during the design process to obtain information about lighting system performance. A designer can use the results of calculations to choose between design alternatives or to refine a particular design. Lighting calculations are mathematical models of the complex physical processes that occur within a lighted space. Since these models can never be accurate in every detail, the computations are approximations of real situations.

The simplest lighting calculation can be performed by hand, whereas the more advanced methods require the use of a computer. More advanced methods generally provide more accurate information. (Accuracy is defined here as the degree to which the calculations agree with reality.)

The type of information that is desired about a lighting system and the complexity of the lighting condition being analyzed determine which calculation method is best applied to the problem. The aspects that must be evaluated in determining the lighting analysis model to use are the following:

Information desired Equipment choice Equipment number and placement Space characteristics

It is the responsibility of the designer to determine and use the most appropriate calculation methods for an application, either a simple average illuminance method or a more complex method to calculate illuminance at a specific point.

The Lumen Method

The Lumen Method described here is the simple average illuminance calculation method, which can be applied to interior spaces where a general uniform lighting system is required. It is a useful tool in two ways; it allows the calculation of the average illuminance when given the number of luminaries to be used in the space, or it can be used to find the number of luminaries required, given the desired average illuminance.

The method does have limitations. The illuminance computed is an average value that is representative only if the luminaries are spaced to obtain reasonably uniform illuminance. The average illuminance determined by the method is defined to be the total lumens reaching the horizontal workplane divided by the area of the workplane. The average value determined this way might vary considerably from that obtained by averaging discrete values of illuminance at several points. The method assumes that room surfaces are diffuse, the illuminance on each surface is uniformly distributed over that surface and that the room is empty.

The workplane is positioned at the height of the visual task. For example, for desk tasks the height is typically assumed to be 0.76 m (2.5 ft.) above the floor. In a space such as a jet aircraft factory, it might be placed at the wing height of the aircraft.

Average Illuminance Equation

The equation for the illuminance in a space is: @(roTa,) x CU x LLF

E , = A v

where:

E, = average maintained illuminance on the workplane

@(TOTAL) = total system lamp lumen output CU = luminaire coefficient of utilization LLF = light loss factor A, = area of the workplane

These terms will be explored in more detail. See also the calculation worksheet, Figure C-1 .

Workplane illuminance (€,)is the average maintained luminous flux striking the workplane per unit area of workplane.

Total System Lamp Lumen Output (@,,,)-refers to the number of initial lumens produced by all lamps within the luminaries that are lighting the space. The lamp manufacturer’s published lumen rating is used for this calculation.

For example, an application is using 10 recessed fluorescent luminaries. Each luminaire has three 32W T8 lamps. The manufacturer’s data on the lamp shows that the initial lumen output of the lamp is 2900 lumens. Thus, the total lamp lumen output ((I ) in the space is

(@,,,,,) = 10 luminaries x 3 lamps/luminaire x 2900 IumensAamp = 87,000 lumens

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Step 1 : Fill in sketch at right

Step 2: Determine Cavity Ratios

* e--% Room Cavity Ratio, RCR =

Ceiling Cavity Ratio, CCR = -- WORK-PLANE-- -

es-% ,eæ-% Floor Cavity Ratio, FCR =

GENERAL INFORMATION

-T hCCJ- ‘-T 1=

-4- ’RC =-

w- - hFC O- A

Project identification: (Give name of area and/or building and room number)

Average maintained illuminance for design:- lux or Lamp data:

Luminaire data:

:- footcandles Type and color:

Number per luminaire:

Total lumens per luminaire: Manufacturer:

Catalog number:

SELECTION OF COEFFICIENT OF UTILIZATION

Step 3: Obtain Effective Ceiling Cavity Reflectance @=) pcc= - - Step 4: Obtain Effective Floor Cavity Reflectance (pFc) PFC e

Step 5: Obtain Coefficient of Utilization (CU) from Manufacturer’s Data CU= - SELECTION OF LIGHT LOSS FACTORS

Nonrecoverable Factors Luminaire Ambient temperature factor Heat extraction thermal factor Voltage to luminaire factor Ballast factor (BF) Ballast lamp photometer factor Equipment operating factor Lamp position (tilt) factor Luminaire surface depreciation factor

Recoverable Factors Lamp lumen depreciation factor (LLD) Luminaire dirt depreciation factor (LLD) Room surface dirt depreciation factor (RSDD) Lamp burnout factor (LBO)

Total light loss factor, LLF (product of individual factors above) = - CALCULATIONS

(Average Maintained Illuminance)

(Illuminance) x (Area) (Lumens per Luminaire) x (CU) x (LLF)

Number of Luminaires =

(Number of Luminaires) x (Lumens per Luminaire) x (CU) X (LLF) (Area)

Illuminance =

Calculated by: Date: Fia. 9-20. Avernnn illiiminnnrin calci ilntinn shed

Figure C-l. Average illuminance calculation worksheet.

70


Recoverable Factors Lamp lumen depreciation factor (LLD) Luminaire dirt demeciation factor íLDD)

Luminaire Coefficient of Utilization (CU)-gives the fraction of lumens that reach the workplane, directly from the light sources and from interreflections. The CU takes into account the efficiency of the luminaire and the impact of the luminaire distribution and the

Floor Cavity Height x ( Length + Width) Length x Width

FCR = 5

Nonrecoverable Factors Luminaire ambient temperature factor Heat extraction thermal factor

Ceiling Caviíy Height x (Length + (Width) Length x Width

CCR = 5

room surfaces in its derivation. Thus, the number of lumens produced by the lamps, multiplied by the CU, determines the number of lumens that reach the workplane. Four factors influence the CU:

Lamp burnout factor (LBO)

The efficiency of the luminaire (b) The luminaire distribution (c) The geometry of the space (d) The reflectances of room surfaces

Ballast factor (BF) Ballast lamp photometer factor Equipment operating factor Lamp position (tilt) factor Luminaire surface depreciation factor

CU values are listed in tables for different room geometries and room surface reflectances. Each luminaire has its own CU table specific to that luminaire’s light distribution and efficiency. Factors (a) and (b) are, therefore, included in all values found in a CU table. Their values are tabulated for various surface reflectances and room cavity ratios (RCRs). The RCR is five (5) times the ratio of total vertical surface area to total horizontal surface area within the room cavity and therefore indicates the relative space proportions.

To find the RCR, either of the following equations can be used: where:

VSA = the sum of the vertical surfaces within the room cavity. This is the sum of the wall areas above the working plane and below the luminaries.

HSA = the sum of the working plane and the luminaire plane areas

Or: The areas in the first equation are the total vertical and horizontal surface areas within the room cavity, which is the space between the luminaries and the workplane. A room may have up to three different cavities (see Figure C-2). The portion of the room that is above the luminaries is called the ceiling cavity, and that portion below the workplane is the floor cavity.

Luminaire plane Luminaire piane J

Figure C-2. The space may be divided into as many as three cavities.

If the luminaries are recessed or surface mounted, there is no ceiling cavity. if the workplane is at the floor level there is no floor cavity.

It is critical to consider only the wall surface area that is within the room cavity as the vertical surface area in determining the RCR. The horizontal surface area refers to the area of the workplane and the luminaire plane and is the same as two times the floor area. The only other room parameters that are needed to obtain a CU value are the room cavity reflectances, which may not be equal to the actual room surface reflectances. Since the Lumen Method considers what occurs only within the room cavity, the ceiling and floor cavities are replaced with their effective reflectances. Effective reflectances model the manner in which these cavities reflect light.

I Room surface dirt demeciation factor íRSDDì I Voltage to luminaire factor I

71


For example, in an industrial application where the luminaries are suspended from the ceiling, the space between the luminaries and the ceiling is the ceiling cavity. Because light that enters the ceiling cavity may reflect off more than one surface before exiting the cavity, the effective reflectance of the ceiling cavity is generally lower than the actual ceiling reflectance. For a floor cavity, where the walls are usually of higher reflectance than the floor, the effective reflectance may be higher or lower than the actual floor reflectance, depending on the space dimensions.

To find the effective reflectance of a floor or ceiling cavity, it is necessary to first find the floor cavity ratio (FCR) or ceiling cavity ratio (CCR). The equations are identical to that for the room cavity ratio, except that the height of the walls within the cavity is used as the cavity height.

The only other information necessary to find the effective cavity reflectances are the cavity surface reflectances. The surface that is opposite the opening to the cavity is called the cavity base. The base reflectance, the wall reflectances, and the cavity ratio determine the effective cavity reflectance. Knowing these pieces of information it is possible to find the cavity reflectance (see IESNA Lighting Handbook, 9th Edition, for detailed information on cavity reflectances.)

Light Loss Factor (LLï,-Since the design objective usually is maintained illuminance, a light loss factor must be applied to allow for the estimated depreciation in lamp lumens over time, the estimated losses from dirt collection on the luminaire surfaces (including lamps), and other factors that affect luminaire lumen output over time. Some differences prevail from initial operation of the system; others change with time. It is important to consider these losses to accurately reflect the system’s performance in the real environment.

operating factor Lamp position (tilt) factor Luminaire surface depreciation factor

A total light loss factor of 0.75 might be applied to many well-maintained commercial buildings having a clean environment. This means that 25 percent (100 minus 75 percent) of the luminous flux that might otherwise reach the workplane is lost due to ballast factor, dirty luminaries, rooms surfaces, and aged lamps. In a dirty manufacturing facility the percentage lost would be higher.

Area of Workplane ( A w p ) I s the area of the entire workplane, which is typically the same as the floor area. The Lumen Method computes an average illuminance over the entire area of the space. In reality, the illuminance will be greatest near the center of the area and slightly less toward the walls for a given uniform layout of luminaries.

Light loss factors are divided into two groups: recoverable and non-recoverable. (See Figure C-3.) Recoverable factors can be affected by maintenance, such as cleaning and relamping luminaries, or by cleaning or painting room surfaces. Nonrecoverable factors are those attributed to equipment and site conditions and cannot be changed with normal maintenance. The total LLF is simply the product of the individual factors. For more information on the various factors, see the IESNA Lighting Handbook, 9th Edition, 2000.

Calculating the Number of Luminaries

It is important to know not only how to calculate the illuminance from a specific number of luminaries in a space, but also how to determine the required number of luminaries to meet a desired illuminance. The number of luminaries required is calculated by rearranging the Lumen Method equation.

Number of Luminaires = 4, x E,,

lumens i lampx lampshminairesx CU x LLq,,,,,)

Recoverable Factors Nonrecoverable Factors Lamp lumen depreciation factor (LLD) Luminaire ambient temperature factor Luminaire dirt depreciation factor (LDD) Heat extraction thermal factor Room surface dirt depreciation factor (RSDD) Voltage to luminaire factor Lamp burnout factor (LBO) Ballast factor (BF) Ballast lamp photometer factor Equipment

72

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