CITY HVAC Design Guide Appendices

Design Guide of HVAC Services - Appendices

APPENDIX A

DESIGN CRITERIA FOR COOLING/HEATING LOAD & MECHANICAL VENTILATION

SF HVAC Design Guide - Appendices March 2007 Page 1 of 41


Space Summer Winter Fresh Air People Lighting Miscellaneous Noise Check

Room Temp. Room RH Room Temp. Requirement Density Load Load Criteria Figure (C db) (%) (C db) (l/s/person) (m2/person) (W/m2) (W/m2) (NC) (ft2/TR)

Office (general) 24 50-55 22 10 9 (perimeter zone) 6 (interior zone)

20-40 25 35-40 200-250

Office (hi-tech) 24 50-55 22 10 9 (perimeter zone) 6 (interior zone)

25-40 50-70 35-40 150-200

Conference room 24 55 22 10 2 20-40 25 30-35 180-200Chinese restaurant 22 60 20 10 1 90 10 sensible/person

10 latent/person (for meal)

45 80-100

Western restaurant 22 60 20 10 1.5 54 10 sensible/person10 latent/person

(for meal)

40-45 80-100

Coffee shop/Bar/Lounge (not for meals)

24 60 22 15 1.5 54 10 35-40 100-120

Canteen/Food plaza 22 60 20 10 1 45 10 sensible/person10 latent/person

(for meal)

45 80-100

Banquet room 22 60 20 10 1 80 10 sensible/person10 latent/person

(for meal)

35-40 80-100

Kitchen (thro' spot cooling) --- --- (no heating)

(thro' kitchen ventilation)

--- --- --- --- ---

Retail shop 24 55 22 10 2.5 40-80 40 40 130-150Supermarket 24 55-60 22 10 12.5 20-40 5-10 40 200Shopping arcade 24 55 22 10 2.5 45 25-40 40-45 130-150Toilet/Changing room (with AC)

26 --- 20(or no heating)

(thro' toilet ventilation)

--- 15-40 --- 40-45 300

Cinema 24 55 22 10 1(or number of seat)

--- --- 30 13 persons/TR

Store room (with AC)

24-26 55 ---(no heating)

10 20 15-40 --- 45 250-300

Computer room (PCs/terminals mainly)

20 50 20 10 6-10 15-40 450-750 35-40 60-80

Computer room (mainframe mainly)

20 50 20 10 10-15 15-40 500-900 35-40 60-80

Hotel guest room 24 55 22 30 l/s per room 2 people per room (or designed

accommodation capacity)

500 W per room 900W per room 30 250-350


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HVAC Design Guide - Appendices March 2007 Page 3 of 41

Space Summer Winter Fresh Air People Lighting Miscellaneous Noise Check

Room Temp. Room RH Room Temp. Requirement Density Load Load Criteria Figure (C db) (%) (C db) (l/s/person) (m2/person) (W/m2) (W/m2) (NC) (ft2/TR)

Corridor 24-26 55-60 20-22 0.25 l/s/m2 --- 15-20 --- 35 for hotel40 for office

300-400

Main entrance/Large lobby

24-26 55-60 20-22 1 l/s/m2 --- 45 --- 40 300

Lift lobby 24-26 55-60 20-22 1 l/s/m2 --- 45 --- 40 300

Health Club 24 60 22 13 8-10 45 --- 40-45 100-120Multi-function room 24 55 22 10 1.5 54 40 30 80-120Back-of-house area 24-26 55-60 ---

(no heating) 8 4 15-40 20 40-45 200-250

Disco/Dancing hall/Ballroom

22 55 20 13 1 54 40 45 70

Karaoke room 24 55 22 10 1.5 15-45 40 40-45 150-200Bank hall 24 55 22 10 1.5 15-40 10 35-40 160-180Bank vault 24 55 22 min. 2 air change --- 15-40 --- 30-35 250 Hospital ward room 24 55 22 10 8-10 15-40 20 30 200Hospital operating theatre (100% OA)

20-24 50-60 20-24 All OA(i.e. quantity of OA

= SA)

4-6 60-80 40-60 30 40

Hospital consultation room

24 55 22 10 4.5 15-40 10 30-35 200

Clinic 24 55 22 10 1.5 15-40 10 30-35 180-200Pantry 26 60 20 --- --- 15-20 40 40-45 250-300Refuse room (with AC) 18 --- ---

(no heating) --- --- 15-20 --- 45 200-250

Plant room (central or large one with AC)

26-28 --- ---(no heating)

min. 2 air change (for operators always there)

--- 15-20 Refer to heat dissipation of the

plants

50 200-300

Table A1: Indoor Design Criteria of Different Kind of Spaces and Their Corresponding Check Figures

Design Guide of HVAC Se

SF

Remarks a. The design criteria listed here are for reference only. Please follow the Code of Practice for Energy Efficiency of Air Conditioning Installations and

Performance-based Building Energy Code first. b. Tolerance for control of temperature: 2C; for RH: 10% c. Due to the temperature climate in Hong Kong, winter room RH is not critical in design so that it is not included here. d. Range of NC depends on the class of space. e. Check figures are solely used for reference, and provide quick preliminary estimation or cross checking of the detailed calculation results. f. This table is mainly applied to Hong Kong and the adjacent areas with similar climate. For those cold areas/countries which also rely on heating in cold season, the

winter design temperature (even RH) for all spaces should be specified at a certain level (min. 5 C to prevent frost).


Space Recommended

Air Change / Hour Type of System

Toilet (a) 12-15 or (b) 90% of OA

(a) Extract or (b) Balanced with 10% deficiency

Refuse room (no AC) 20-30 Extract or Balanced with 10% deficiency

Kitchen 60-80 or refer to kitchen consultant's requirement

Extract (for small kitchen) or Balanced with 10% deficiency (for large kitchen)

Plant room (no AC) 15 Extract or Balanced Transformer room For substation on G/F or

above, 3500 m3/h for each 1500 kVA capacity

For basement substation, 7000 m3/h for each 1500 kVA capacity

(Refer to the latest COP of CLP/HKE for details.)

Extract

Lift machine room Refer to heat dissipation of engine (min. 20)

Extract

Carpark (above ground surrounded with parapet walls)

6 Extract

Carpark (enclosed or underground) 7 (residential) 8 (commercial offices) 9 (entertainment/shopping plaza) (Also refer to the latest Practice Notes on Control of Air Pollution in Car Parks for details.)

Balanced with 30% deficiency (make-up air from the main entrance/exit, but need to countercheck the air velocity through there not too high)

Table A2: Design Criteria of Mechanical Ventilation



APPENDIX B

HVAC LOAD CALCULATION



HVAC Load Calculation

Weather Data

Design Criteria

Internal Heat Gains

Construction and Materials

Schedules

B1. Typical Design Loads

Design space load, zone load, system load and plant load are the respective cooling loads from the space, system/zone and plant.

Plant is a collection of systems; system/zone is a collection of spaces; while space is the basic area for load calculation.

Generally, Plant load System/zone load Space load For air conditioning purpose,

Plant load is used to size the respective chiller plant, the associated chilled water pumps and the main chilled water pipes.

System/zone load is used to size the respective air side system, mainly the cooling coil and fan of the AHU/PAU. In general a zone would be handled by an independent temperature/humidity control.

Space load is used to size the respective air side equipment serving the space, mainly the air diffusers/grilles; VAV boxes (for VAV system); FCUs (for fan coil system), etc.

Block load vs. Peak load Block load is an overall load that includes the simultaneous load profiles of

different areas. Peak load is the maximum load of a certain area according to its own load

profile. Generally, Block load Peak load



B2. Cooling Load Temperature Difference / Solar Cooling Load / Cooling Load Factors (CLTD/SCL/CLF)

Data obtained by using the TFM on a group of representative applications were used to generate Cooling Load Temperature Difference (CLTD) data, for direct one step calculation of cooling load from conduction heat gain through sunlit walls and roofs and conduction through glass exposures. Solar Cooling Load (SCL) is used to approximate cooling loads due to solar radiation transmitted through fenestration. Cooling Load Factor (CLF) for similar one step calculation of solar load through glass and for loads from internal sources. These CLTDs, SCLs and CLFs include the effect of time delay caused by thermal storage.

Load calculation is simplified with the use of one step CLTD/SCL/CLF method, and it is convenient to use tabulated CLTD, SCL and CLF data based on weighting factors generated from representative spaces in offices, schools and dwellings. However, the weighting factors are quite sensitive to variation in space construction and related conditions. It is more appropriate for users to develop custom CLTD/SCL/CLF tabular data for specific projects or types of building to reflect current design and local construction practices.

B3. Application Software

Commercial packages i.e. Trane Trace 600, Carrier E-20II Hourly Analysis

Programme, Hevacomp etc. are commonly used in the local industry. Some companies may have their own developed software. Carrier E-20II is available in the BST Design Studio for learning and final year design project.

B4. Output Interpretation

The outputs of HVAC software should be properly understood and interpreted. Dont think the software would always give you the correct answers, since your inputs may be wrong. Owing to this, it is important to perceive the correctness and reliability of the outputs through the followings: Block cooling/heating load Check figures (ft2/TR or m2/kW) (1 m = 3.28 ft, 1 TR = 3.516 kW) Ratio of Qtransmission : Qinternal : Qventilation (35:45:20 for typical office) Hourly/monthly load profiles Psychrometric cycle (esp. typical area) These checking outputs can be extracted from Air System Sizing Summary; Zone Sizing Summary; Air System Design Load Summary; and Cooling Plant Sizing Summary of Carrier E20-II. For details of the output reports, always check from the online-help of E20-II.



WORKED EXAMPLE Sample Building Building Type Office Building, 20/F (1-19/F typical, 20/F the top floor right below

the roof), overall floor plan size: 36m x 36m floor to floor ht. = 3.5m, window ht. = 1.6 m, wall ht. = 1.9 m

Walls: External: 100 mm concrete, 20 mm plaster on both side, mass = 320 kg/m2, overall U-value is 1.5 W/m2K, Group "D" wall Partition: 15mm gypsum board, 50mm air layer, 15 mm gypsum board, U-value is 1.71 W/m2K

Roof: Screeding, 37 mm polystyrene insulation, asphalt, screeding, 150 mm concrete, overall U-value is 0.8 W/m2K

Floor: Carpet, screeding, 100 mm concrete

Glazing: Curtain wall panel, U-value is 5.5 W/m2K, Shading Coefficient = 0.45

Internal load Occupancy density = 7m2/person Lighting density = 20 W/m2, (a =5.5, b = 'C') Equipment load = 15 W/m2

Ventilation & infiltration

10 l/s per person nil infiltration

Operating hours

9:00am to 6:00pm

Summer design conditions

Outdoor: 33oC db, 28oC wb Indoor: 25oC db, 50% RH

Sample Building

N

Non air conditioned space 15 m x 15 m

36 m x 36 m Typical Floor Plan for Worked Example Non air-conditioned space with partition 15 m x 15 m Internal zone 4 external zones (N, E, S, W) with 5 m depth from the external wall



APPENDIX C

OTTV



Overall Thermal Transfer Value [Ref.: Code of Practice for OTTV in Buildings 1995, Building Department, HKSAR]

C1 For the design and planning of energy-efficient buildings, Government developing a comprehensive energy code to cover inter alia lighting and air-conditioning. Overall thermal transfer value (OTTV) is one aspect of energy conservation. General approach C2 An OTTV is a measure of the energy consumption of a building envelope. Its formulation allows authorized persons, registered structural engineers and other persons responsible for the design and construction of buildings freedom to innovate and vary important envelope components such as type of glazing, window size, external shading to windows, wall colour and wall type to meet the maximum OTTV criteria. Any measure to improve energy efficiency or to save energy should be considered in planning a building. C3 Siting a building to avoid extensive glazed facades with a southerly aspects or introducing shades to window areas can reduce solar heat gain. Appropriate choice of windows with a low thermal transmittance characteristic will also minimize solar heat transmission. C4 Artificial lighting consumes electricity and creates heat. This increases the cooling load of a building and in turn increases energy consumption. Consequently, when determining the size and location of windows as well as choice of glass in the envelope of a building, efforts should be made to provide as much natural lighting into the building as possible. For example, with glazing, the visible lighting transmittance should be acknowledged in addition to its thermal transmittance properties; daylight can supplement artificial lighting and consequently reduce the cooling load. C5 Other measures include more extensive use of energy-efficient building services equipment and appliances, e.g. energy-saving lamps, low-loss luminaries and high-efficiency air-conditioning and more sophisticated building services control systems.

Useful websites: http://www.info.gov.hk/bd/english/documents/code/e_ottv.htm http://www.info.gov.hk/bd/english/documents/pnap/Pnap172.pdf



APPENDIX D

CHILLER COMPARISON



Characteristic Reciprocating Chiller Twin Screw Chiller Centrifugal Chiller

Max. nominal capacity available in market

Air-cooled: about 400 TR

Water cooled: 340 TR


Water cooled: 1250 TR


Water cooled: about 10000 TR

Common refrigerant

R22 (to be banned in 2030) R134a, R22 (to be banned in 2030)

R134a

kW/TR at full load Highest Middle Lowest

Main capacity control

By cylinder unloader, hence step control

By slide valve, modulating range from 15 to 100%

By inlet guide vane

Multi-stage and economizer application

No Yes Yes

Noise problem More noisy, may require acoustic enclosure

Less noisy Less noisy

Vibration More serious Less serious Less serious

Compressor cycling

Yes No No

Frequency of maintenance

More frequent, due to much more critical parts for maintenance

Highest maintenance cost

Less frequent, due to major moving parts are 2 rotors and slide valve

Less frequent, due to major moving part is rotating impeller

Operating life Shorter Longer Longer

Initial cost in general

Lowest Medium Highest

Table D1: Comparison of Different Types of Chillers



APPENDIX E

PIPES, FITTINGS & ACCESSORIES



E1. Pipes and Fittings Different water circuit would use different type of pipes as follows:

Water Circuit Material Chilled water Black steel Hot water Black steel Condenser water Galvanized steel Condensate drain uPVC

The major fittings will include the following type: Bend Tee Reducer/Expander The pipe connection will have: Union joint Flanged joint Welded joint

E2. Valves

Valves can be used for isolation, regulation, commissioning of water circuits according to their design purpose. The commonly adopted types are: Gate valve (quick-opening): for isolation and on-off purpose. It can be manual

or motorized. Globe valve (linear): for regulation, commissioning and isolation of smaller size

pipework. Butterfly valve (equal-percentage, with linear characteristic after 40%): for

regulation, commissioning and isolation of larger size pipework. Check valve/non-return valve: to confine water flow in one direction. Double regulating valve (linear): for commissioning. Constant flow valve: to keep water flow constant, i.e. not more or less than the

preset value. 3-way valve: to mix or divert the water flow. Angle valve (quick-opening): similar to gate valve, but installed at pipe turning. Ball valve (equal-percentage, with linear characteristic after 40%): similar to gate

valve, but has more linear characteristic. Ball float valve: commonly installed in water tank to stop water flow when the

required water level has been achieved. Solenoid valve (on-off): electric on-off valve.



Gate Valve Globe Valve

Butterfly Valve Check Valve

E3. Measuring Devices

In the water pipework, measuring devices would be installed for monitoring different characteristics of water flow, these will include: Temperature gauge/thermometer Pressure gauge Flow meter

E4. Thermal Insulation

A variety types of thermal insulation are commonly applied in HVAC systems, they include: Phenolic foam (PF) Fibre glass (FG) Hydrous calcium silicate (HCS) Rock wool (RW) Magnesia (MN) Flexible elastomeric pipe insulation (FE) Polystyrene (PS)



Type of System System Equipment/Component Type of Insulation Water Side Chilled Water System Pump Pipe Valves PF/FG Fittings and accessories F & E tank Condensate Drain System Pipe PF/FG Valves, fittings and accessories Hot Water System Pump Pipe PF/FG Valves or Fittings and accessories HCS & RW F & E tank Steam System Pipe Valves PF/FG or MN Fittings and accessories Boiler Flue RW Refrigeration Side Pipework FE

Apart from suitable selection of the insulation type, the following points should also be noted: Pre-formed type is commonly used for pipework insulation. Appropriate thickness is required, as usually determined by the fluid temperature,

pipe diameter, shape of the related components, etc. Vapour barrier coating is necessary together with the usage of thermal insulation. Smoke produced from burning the insulation should be non flammable and toxic. For pipework or ductwork inside plant room or exposed outside, PS would be

used, together with wire mesh/cement plastering and the enclosed casing. For phenolic foam, the thicknesses of insulation to be used for pipework are shown as follows: Pipe Diameter (mm) Thickness of Insulation (mm)50 or below 25 65 - 80 35 100 - 250 40 Above 250 50 For fibre glass, the thicknesses of insulation to be used for pipework are shown as follows: Pipe Diameter (mm) Thickness of Insulation (mm)

Chilled/Heating Water: up to 40 25 50 - 65 40 65 - 300 50 Above 300 65 Condensate Pipes (all): 15



E5. Accessories

Strainer: to remove debris inside the water circuit. Automatic air vent: to purge the air trapped inside the water circuit. Flexible connector: to be installed at the pipework where it is connected with the

vibrating equipment such as pumps. Expansion joint/loop: usually applied at the location where crossing building

joint.

Y-type Strainer (for small installation) Bucket Type Strainer (for large installation)

E6. Typical Connection Arrangement of Equipment Upstream (In) Downstream (Out) Pump Gate valve

Strainer Pressure gauge Flexible conncector Reducer (eccentric)

Expander (eccentric) Flexible connector Pressure gauge Check valve Control valve (on-off) Globe valve (or butterfly valve)

Cooling coil of AHU/PAU Gate valve Strainer Temperature gauge Flexible connector

Flexible connector Temperature gauge Control valve (modulating) Globe valve

Cooling coil of FCU Gate valve Control valve (on-off) Globe valve

Chiller Gate valve Temperature gauge Flexible conncector

Flexible connector Temperature gauge Flow switch Control valve (on-off) Globe valve (or butterfly valve)



APPENDIX F

PIPE & PUMP SIZING



CHILLED WATER PIPE & PUMP SIZING (& CONDENSATE DRAIN PIPE) 1. Decide the air side and water side equipment and their installation location. 2. Determine the coil load according to the peak space load for FCU, or the block/zone

load for AHU/PAU. Then the water flow rate of each air side equipment (FCU, PAU or AHU) can be determined by the following equation:

)TT(cmQ inoutpw = &

where, Q: coil load (kW)

&m: chilled water flow rate (l/s) cpw: specific heat capacity of water, 4.18 kJ kg

-1K-1

(Tout - Tin): difference of chilled water out of and into the coil, typically 5.5 C (for 12.5 C out and 7 C in)

3. Decide the Hydronic System to be used. 4. Draw the sketch of main pipes, risers, headers, branches, from the chiller and pumps

to the air side equipment. 5. Indicate the water flow rate of each equipment. 6. Determine the size of pipes by:

pressure drop: 100 - 400 Pa/m, preferably around 250 Pa/m velocity: 1 - 3 m/s, preferably around 1.2 m/s

(for steel pipe, refer to Fig. 1 of Ch. 35 of 2001 ASHRAE Fundamentals Handbook, or the latest edition).

7. Determine the pressure drop of various pipe fittings and accessories (refer to Tables 1

and 2 of Ch. 35 of 2001 ASHRAE Fundamentals Handbook, or the latest edition). In addition, determine the pressure drop of the chiller evaporator, cooling coil of air side equipment, and control valve at air side equipment. The pressure drop of evaporator and coil can be found from the catalogues of chiller and AHU respectively. The pressure drop of modulating control valve should be determined from the approach of valve authority (to be discussed in BST20532 HVAC Services 2).

8. Identify the index circuit (or critical path) of the system. 9. Apply the safety factor where appropriate (usually 10-20%). 10. Size and select the pump according to pump curve. Usually horizontal split casing

pump would be selected, in order to facilitate the frequent needs of maintenance. 11. Dont forget to size the condensate drain pipes from the FCUs, PAUs or AHUs, with

reference to Table F2. In particular those for FCUs, careful planning for the pipe run is essential, since the minimum recommended fall of condensate drain pipe is 1:200, so this pipe cannot run too long due to the limited space between beam and



SF

rvices - Appendices


false ceiling. Therefore it should be directed to the places with drainage facilities (e.g. toilet or pantry) as soon as possible. If no such places nearby, additional pipe ducts may be needed within the main function area, in order to accommodate the condensate drain stack. The condensate drain stacks are commonly connected to waste water drainage system before reaching the last manhole.

CONDENSER WATER PIPE & PUMP SIZING (& MAKE-UP WATER TANK) Since launching the Pilot Scheme for Wider Use of Fresh Water in Cooling Towers by WSD and EMSD in 2000, water-cooled chiller plant becomes popular for the new building projects, in lieu of the air-cooled one which was used in the past by default. The criteria of sizing condenser water pipe are same as item (6) in the last section for chilled water pipe. However the heat balance equation in item (2) should be used carefully, the discrepancies of condenser water design from that of chilled water are as follows: y Q should be the heat rejection rate of the chiller. Remember the fundamental of vapour

compression refrigeration cycle: Qheat rejected from condenser = Qheat absorbed at evaporator + Wcompressor y (Tout - Tin) is commonly 6 C, since Tout = 38 C and Tin = 32 C for condenser water. y In case of sea water cooling, specific heat capacity cpw should be that of sea water,

instead of fresh water. cpw of sea water is 3.62 kJ kg-1K-1. Apart from the pressure drop of chiller condenser, pipe, fittings and accessories (modulating control valve not commonly installed) for condenser water pump sizing, the involved static head should be incorporated. Note that the typical condenser water circuit with cooling tower (CT) is an open circuit, not a closed circuit like the chilled water system. Therefore the static head to lift up the condenser water from the pump level (usually designed at basement or G/F) to the cooling tower level (usually designed at open space or roof) should be considered, similar to the idea of potable water supply system delivering water from sump tank to roof tank. Such static head should be very large, luckily with the compensation of the water column between the basin of cooling tower down to the suction of condenser water pump, the actual static head for condenser water circuit Ps,cw can be determined as follows: Ps,cw = Ps,pump discharge to CT nozzle Ps,pump suction to CT basin = g (hCT nozzle hpump discharge) g (hCT basin hpump suction) = g (hCT nozzle hCT basin) since hpump discharge = hpump suction The vertical distance (hCT nozzle hCT basin) depends on the configuration and size of cooling tower, this can be easily found from the catalogue. Dont forget to size the make-up water tank for the condenser water circuit, since there is continuous water loss mainly from evaporation (due to evaporative cooling) when the cooling tower is in operation. The total water losses (including drift loss and bleed-off) may account for 1% of the condenser water flow rate. According to design practice, a 4-hour water storage would be provided for this make-up purpose.

rvices - Appendices


QUICK-CHECK TABLES Tables F1 and F2 provide a quick-check of sizes of both the chilled water pipes and condensate drain pipes. For condenser water pipes, please directly use flow rate in Table F1 for pipe sizing purpose, NOT the left part of table under the heading of Cooling Load.

Cooling Load Flow Rate Pipe Size Velocity Pressure T = 5 C T = 5.5 C T = 6 C Drop

kW TR kW TR kW TR l/s mm m/s Pa/m 4.0 1.1 4.4 1.2 4.8 1.4 0.189 20 0.6 2507.9 2.3 8.7 2.5 9.5 2.7 0.378 25 0.7 30015.9 4.5 17.5 5.0 19.1 5.4 0.756 32 0.8 27023.8 6.8 26.2 7.5 28.6 8.1 1.135 40 0.9 26046.2 13.1 50.8 14.5 55.4 15.8 2.2 50 1.1 28079.8 22.7 87.8 25.0 95.8 27.2 3.8 65 1.2 250132 37.6 146 41.4 159 45.2 6.3 80 1.3 250294 83.6 323 92.0 353 100 14 100 1.7 260525 149 578 164 630 179 25 125 2.0 280861 245 947 269 1033 294 41 150 2.3 2601596 454 1756 499 1915 545 76 200 2.3 2002247 639 2472 703 2696 767 107 250 2.3 1203570 1015 3927 1117 4284 1218 170 300 2.3 1204221 1201 4643 1321 5065 1441 201 350 2.3 1105292 1505 5821 1656 6350 1806 252 400 2.3 807287 2073 8016 2280 8744 2487 347 450 2.3 809009 2562 9910 2819 10811 3075 429 500 2.3 7010500 2986 11550 3285 12600 3584 500 550 2.3 6012600 3584 13860 3942 15120 4300 600 600 2.3 53

Table F1: Chilled Water Pipe Sizing Table (for Quick-check Only) Condensate Drain (mm) 25 32 40 50 80 100Pipe Sizing TR 5 30 50 170 300 430

Table F2: Condensate Drain Pipe Sizing Table


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APPENDIX G

DUCTS, GRILLES, FITTINGS & ACCESSORIES



G1. Ducts and Fittings The type of ducts used in HVAC contain: Rectangular duct: fabricated at site so the most flexible to fit space, but highest

pressure loss. Circular duct: prefabricated, lowest pressure loss. Oval duct: prefabricated, medium pressure loss but suitable for tight ceiling

space. Flexible duct: usually circular, and for flexible connection between main duct

and equipment. The material used for ductwork depends on the carrying air characteristics and usage:

Characteristics/Usage Material General Galvanized steel Fire rated Promat or Dura Steel Kitchen exhaust Stainless steel Corrosive uPVC

The fittings will include the following type: Bend Tee Reducer/Expander (also called transformation) Wye

G2. Air Grilles and Diffusers

To distribute or remove the conditioned air effectively, different type of grilles are applied: Square diffuser: generally applied, especially to suit the 600 x 600 ceiling grid.

This may be 1-, 2-, 3- or 4-way flow. Slot diffuser: adopted in VAV (variable air volume) system due to its longer

throw distance. Circular diffuser: similar usage as slot diffuser. Linear air grille: for continuous air supply or coordination with the interior

design. Return/exhaust air grille/register: to remove air from the air-conditioned space.

For return air grille/register, the air is back to AHU or FCU; for the exhaust one, the air will be thrown outside of the building.

Door louvre: installed for transferring air through door instead of ductwork. External louvre: mounted at external wall for fresh air intake or exhaust air

outlet. Jet nozzle: to supply conditioned air at long distance, usually more than 10 m.



Square Diffuser Slot Diffusers (Troffers) Circular Diffuser

Return Air Grille Return Air Grille (with Filter) Supply Air Grille

External Louvre Jet Nozzle Laminar Flow Diffuser

In the selection of the required air grilles or diffusers, the followings are the major design criteria: Air volume flow rate Throw Drop Air velocity/noise criteria/pressure drop limitation

G3. Dampers

Dampers, similar to the valves in water pipework, can be used for isolation, regulation, commissioning of ductwork according to their design purpose. The common types include: Volume control damper: for isolation, regulation and commissioning purpose.

This can be manual or motorized. Fire damper: to stop fire/smoke spread and form part of the fire

compartmentation. Splitter damper: applied at wye to commission the air flow to/from 2 directions. Non-return damper: to confine the air flow in one direction. Constant flow damper: to keep the air flow constant, i.e. not more or less.



Fire damper: to stop fire spread and form part of the fire compartmentation, and activated either by the fire signal from the central fire control panel or by the fusible link.

Smoke damper: to stop the spread of smoke in case of fire, and activated when fire signal is received at the central fire control panel.

Air valves which can regulate the air amount are alternative to the dampers, however they are more expensive.

Parallel Bladed Volume Control Damper Opposite Bladed Volume Control Damper

Smoke Damper Fire/Smoke Dampers

G4. Measuring and Control Devices

In the ductwork, measuring devices would be installed for monitoring different characteristics of air flow, these will include: Temperature sensor Pressure sensor Orifice or venturi: to measure the air volume flow rate. Thermostat: to keep the room air temperature at the preset value (e.g. 24 C) Humidistat: to maintain the room air relative humidity at the preset value (e.g. 50

%RH)



G5. Accessories

Apart from some accessories mentioned in the part of basic components, there are more: Silencer: usually installed at the outlet of duct section of AHU or PAU, so as to

maintain the supply air at the design noise level. Internal lining: wrapped on the inner surface of ductwork for acoustic

requirement. Flexible connector: to be installed at the ductwork where it is connected with the

vibrating equipment such as fans. Thermal insulation: to prevent heat loss/gain of the transferred air of the system.

Apart from wrapping the required ductwork, it is also for the related equipment. The types include: fibre glass: for general ductwork polystyrene: for plant room and externally installed ductwork thermal board: directly used to construct ductwork Refer to D4 of Appendix D for more information about thermal insulation.

Access panel: to access inside the ductwork for maintenance.

Silencers Access Panel



APPENDIX H

AIR DISTRIBUTION DESIGN



DESIGN PROCEDURES 1. Determine the air volume flow rates based on load calculation. For VAV systems,

evaluation should include the range of flow rates from minimum occupied to design load.

2. Select the tentative diffuser type and location within the room. 3. Determine the room's characteristic length L (refer to Table 3 of Ch. 32 of 2001

ASHRAE Fundamentals Handbook, or the latest edition). 4. Select the recommended T0.25/L ratio (refer to Table 4 of Ch. 32 of 2001 ASHRAE

Fundamentals Handbook, or the latest edition). 5. Determine the throw distance T0.25 by multiplying the selected T0.25/L by L. 6. Select the appropriate diffuser size from the manufacturer's catalogue based on T0.25,

together with other necessary criteria such as the noise level, outlet velocity and/or pressure loss limitation.



APPENDIX I

DUCT & FAN SIZING



DUCT SIZING PROCEDURES Duct sizing methods:

o Equal-friction method o Empirical-velocity method o Static-regain method o T-method

Useful information for duct sizing:

o Circular duct sizing chart (refer to Fig. 9 of Ch. 34 of 2001 ASHRAE Fundamentals Handbook, or the latest edition).

o Change of duct size from circular to rectangular (refer to Table 2 of Ch. 34 of 2001 ASHRAE Fundamentals Handbook, or the latest edition).

o Velocity limitation at different NC levels (refer to Table F1).

Ductwork Velocity (m/s) Design Noise

Criteria Riser / Dropper

in Shaft and Main Header

Main Branch in Ceiling Void

Runout to Diffuser

Diffuser and Diffuser

Plenum Boxes

Return / Extract Grille

NC30 7 3.5 3.0 2.0 2.5 NC35 8 4.0 3.5 2.5 3.0 NC40 9 4.5 4.0 2.5 3.0 NC45 10 5.0 4.5 2.5 3.0 NC50 10.5 6.0 5.0 3.0 3.5 NC55 10.5 6.5 6.0 3.0 3.5

NC60 and above 11.0 7.0 6.0 3.5 4.0 External Louvres --- --- --- --- 3.5 for Exhaust

2.5 for Intake

Table I1: Maximum Velocity for Ductwork in Respect to NC Level Useful information for fan sizing:

o Loss of fittings and accessories (for rectangular fittings refer to Tables CR3-1 to SR7-17 of Ch. 34; for round fittings refer to Tables CD3-1 to SD5-25 of Ch. 34 of 2001 ASHRAE Fundamentals Handbook, or the latest edition).

o Total fan static pressure = P straight duct + P fittings + P accessories + P equipment + P air terminal units + P miscellaneous

o Total fan pressure = Total fan static pressure + Fan outlet velocity pressure

o Apply the safety factor where appropriate (usually 10-20%, not for equipment and terminals).



WORKED EXAMPLE Air Side Design

1

3 5

4 2

AHU Smooth Elbow

Diverging Tee

Wye

RAD

External Louvre SAD

OAD

N

Useful Information The AC area is 6000 mm 9000 mm, each grid is 1500 1500 mm. The east side is an external wall, and the perimeter zone is 3 m from this wall. 600 600 supply air diffusers would be used. A separate plant room is used to install the AHU, the west side is also an external wall

and the outdoor air can be acquired through the external louvre. For the components of the AHU, from upstream to downstream, they are the mixing

plenum, panel filter, cooling coil and centrifugal fan. A silencer would be installed at the outlet of AHU and within the plant room.



APPENDIX J

TYPES OF PUMPS & FANS



J1. Types of Water Pumps

These are the essential equipment to circulate and pressurize the chilled, condenser or hot water of HVAC systems for cooling or heating purpose. The common types are: Horizontal split casing pump Vertical split casing pump End suction pump In line pump

Horizontal Split Casing Pump The Cover Removed for Maintenance

End Suction Pump In-line Pump



J2. Types of Fans These are the essential equipment to drive and pressurize the air for cooling, heating or ventilation purpose. The common types are: Centrifugal fan Axial fan Propeller Cabinet fan



APPENDIX K

TYPICAL SYSTEM CONTROL ARRANGEMENT



K1. Water Side System

Chillers Part load operation (by designed leaving chilled water temperature) Fail safe control (during power failure, chillers set to no load) Constant flow control Chillers & water pumps Sequencing control (with overlapping operation margin) Changeover to standby pump On-off interlock (by decoupler or energy meter) Start-stop sequencing control (start: PPMVCH; stop: CHPPMV) Skip control

K2. Air Side System Air Handling Units (AHUs)

S.A.R.A.

T

CH.W.R.CH.W.S.

C.C.

F.A.

Primary Air Units (PAUs)

P.A.F.A.

T

CH.W.R.CH.W.S.

C.C.

Fan Coil Units (FCUs)

S.A.

R.A.

CH.W.R.CH.W.S.

C.C.

TS



K3. Override Control The override control would be provided to completely shut down the mechanical ventilation and air conditioning equipment stipulated by FSD requirement of each floor by the common fire signal. An override control panel which is installed and located adjacent to the central fire control panel would include the following provision: automatic shut down control (activated by fire signal) manual/auto mode selector manual on/off switch manual reset

K4. Control Centres K4.1 Building Management System (BMS)

Due to the sophsiticated and user-friendly nature of the computer, BMS becomes the standard provision of the overall HVAC systems, as well as other building services systems or any building operation and management installations in Hong Kong SAR. Standard softwares for this purpose are easily available and comparable. The development of the open system communication protocol BACnet enhances the integration of different control components and equipments from different manufacturers, that in turn guarantees to fulfill the requirements of any control provisions. You are advised to keep abreast in this aspect through retrieving information from latest engineering journals and catalogues.

K4.2 Central Control Console (CCC)

If BMS is not applied, a CCC would be provided for the purpose of central control of the entire HVAC systems. The CCC is usually installed in the AC Control Room, it is a free standing control station with a mimic diagram and all related control and monitoring provision. The main details are stated as follows. Mimic Diagram To indicate the schematic of water/air side of HVAC systems and include a set of status indicating lights and associated test buttons for each of the ensuing equipment: chillers pumps boilers (where applicable) calorifiers (where applicable) cooling towers (where applicable) energy meter (for differential bypass system only) flow meter (for decoupler system only) AHUs PAUs main ventilating fans motorized valves chemical feed pumps



Control Panel for Equipment For each of the aforesaid equipment, a set of control and monitoring provisions include: on-off push button (remote control) running-hour meter timer (where necessary) General Provisions display of chilled water temperatures at inlet/outlet of each chiller, main supply

pipe and main return pipe. recorder for daily temperature profile of main chilled water supply/return,

start/stop frequency of chillers and cooling load of plant. electric quartz clock

K4.3 Local Motor Control Panel (LMCP)

The CCC can be used to centrally and remotely control all main equipment of HVAC systems, however a LMCP would be also provided nearby each equipment to allow local control for maintenance or operation purpose. Common provisions on the front panel of a LMCP include: power on indicating light ON indicating light FAULT indicating light local/remote selector switch on/off push button filter clog indicating light (where necessary) ammeter voltmeter



APPENDIX L

PACKAGED & UNITARY EQUIPMENT



L1. Packaged Type Air Conditioning Units

The packaged type air conditioning units are very commonly used in the premises under 100 TR. The main feature of this equipment is that air ductwork can be directly connected from this unit without connecting chilled water supply, but conditioned air can be provided. Basically it contains three of the four essential components in a refrigeration system evaporator, compressor and expansion device. Since it has nearly included the whole refrigeration system, it is called the packaged unit. For the configuration of the remaining component condenser, there are two types of packaged units, depending on the heat rejection approach, as follows.

a. Air-cooled Packaged Type Unit

Typically it is installed at rooftop and conditioned air is delivered from there to different floors of the building. Usually it is applied in low-rise building or premises in which open space is available to install this unit for air-cooling purpose.

On the other hand, sometimes the term air-cooled packaged unit may be applied to the air conditioning equipment used in central computer rooms. However the usage of such term is not exact, and in fact for this equipment, the condenser is separated from the main body and installed as an outdoor unit together with a cooling air fan, therefore it is similar to the configuration of a split type air conditioner, but just providing larger cooling capacity.

Indoor Unit Outdoor Unit



b. Water-cooled Packaged Type Unit The condenser is installed inside the main body of the packaged unit, and a pair of cooling water pipes is connected to it for heat dissipation purpose. This is commonly used in scheduled premises in Hong Kong, such as restaurants, cinemas, industrial processes, etc., where fresh water is legally available for cooling purpose.

L2. VRV Systems

VRV (Variable Refrigerant Volume) System has been prevailing in Hong Kong for decade, in fact this system has been widely used even in high-rise buildings in Japan for long time. Basically it is a split type air conditioner, however only one outdoor unit can centrally handle more than 10 nos. of indoor units. Since during partial load of the area served by each indoor unit, the refrigeration system would be turned off or operating in half speed, then the refrigerant flow for this indoor unit should be reduced. Then the centralized outdoor unit would vary the flow to that indoor unit and the overall refrigerant flow would be adjusted accordingly.


APPENDIX ADESIGN CRITERIA FORCOOLING/HEATING LOAD &MECHANICAL VENTILATIONAPPENDIX BHVAC LOAD CALCULATIONAPPENDIX COTTVOverall Thermal Transfer ValueGeneral approach

APPENDIX DCHILLER COMPARISONAPPENDIX EPIPES, FITTINGS & ACCESSORIESE1. Pipes and FittingsE2. ValvesE3. Measuring DevicesE4. Thermal InsulationSystem Equipment/Component

E5. AccessoriesE6. Typical Connection Arrangement of Equipment

APPENDIX FPIPE & PUMP SIZINGCHILLED WATER PIPE & PUMP SIZING (& CONDENSATE DRAIN PIPE)CONDENSER WATER PIPE & PUMP SIZING (& MAKE-UP WATER TANK)QUICK-CHECK TABLES

APPENDIX GDUCTS, GRILLES, FITTINGS & ACCESSORIESAPPENDIX HAIR DISTRIBUTION DESIGNDESIGN PROCEDURES

APPENDIX IDUCT & FAN SIZINGDUCT SIZING PROCEDURES

APPENDIX JTYPES OF PUMPS & FANSJ1. Types of Water Pumps

APPENDIX KTYPICAL SYSTEM CONTROL ARRANGEMENTK1. Water Side SystemK2. Air Side SystemK3. Override ControlK4.1 Building Management System (BMS)K4.2 Central Control Console (CCC)K4.3 Local Motor Control Panel (LMCP)

APPENDIX LPACKAGED & UNITARY EQUIPMENT

CITY HVAC Design Guide Appendices

Documents

room rh room

toiletchanging room

personstrstore room

refuse room

banquet room

conference room

karaoke room

hospital ward room