Catalog 219 RoofPak ™ Singlezone Heating and Cooling Units With Evaporative Condensers See page 1 MEA 368-93-N Type RPE/RDE 75 to 150 Tons RPE = DWDI Airfoil SAF Blow Through or Draw Through Cooling Coil / Filters Gas, Electric, Steam or Hot Water Heat RDE = SWSI Airfoil (Plenum) SAF Draw Through Cooling / Filters Steam or Hot Water Heat
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Catalog 219
RoofPak™ Singlezone Heating and Cooling UnitsWith Evaporative Condensers
See page 1
MEA368-93-N
Type RPE/RDE75 to 150 Tons
RPE = DWDI Airfoil SAFBlow Through or Draw Through Cooling Coil / FiltersGas, Electric, Steam or Hot Water Heat
RDE = SWSI Airfoil (Plenum) SAF Draw Through Cooling / FiltersSteam or Hot Water Heat
Cat 219 1
A New Standard in Rooftop Systems with Evaporative Condensers• 75 through 150 tons.
• Full factory operation test.
• 100% make-up air, dehumidification, VAV or CV operation.
• Modular construction and customized application flexibility.
• Multiple fan, coil, filter and heat selections. High efficiency compressor and coil combinations.
• Factory integrated and commissioned MicroTech II™ advanced DDC control system.
• McQuay’s innovative Protocol Selectability™ feature provides building automation system interoperability with BACnetá and LonMarká communications capability.
• Durable, double-wall construction with access doors on both sides of each section.
• Heavy-duty evaporative condenser designed for easy maintenance with a walk-in service compartment
• Blow through configuration for high sensible cooling and quieter operation.
• Draw through configuration for high latent cooling or high humidity applications.
Agency Listed
Nomenclature
ContentsMcQuay’s unique features and options . . . . . . . . .2
“HI-F,” “MicroTech II,” “RoofPak,” “Protocol Selectability,” “SpeedTrol,” “VaneTrol,” “DesignFlow,” “SuperMod,” and “UltraSeal” are trademarks and “McQuay” is a registered trademark of McQuay International, Minneapolis, Minnesota.
changes in design and construction at anytime without notice.
MEA368-93-N
Manufactured in a ISO-Certified
Facility
R P E - 150 C S E
RoofPak
Unit Configuration
P = Blow through CoolingD = Draw through Cooling
Evaporative Condensers
Heat Medium
A = Natural GasE = ElectricS = SteamW = Hot WaterY = None (Cooling Only)
Design Vintage
Nominal Capacity (Tons)
RPE, RDE: 076, 089, 100, 110, 130, 140, 150
Cooling Coil Size
S = Standard (Low Airflow)L = Large (High Airflow)
Document Number: Cat 219
2 Catalog 219 Catalog 219 3
SuperMod High Turndown Gas Burner
• Full 20:1 turndown and multiple sizes enable precise temperature control at reduced design, installation, and life-cycle costs.
• Maintain comfortable tenant environment in VAV, 100% make-up air, and dehumidification applications.
MicroTech II™ Control System
• Factory-installed and tested to minimize costly field commissioning.
• Protocol Selectability™ feature for easy integration into the BAS of your choice using open, standard protocols such as BACnet® or LonTalk®.
• Easily accessed for system diagnostics and adjustments via a unit mounted keypad/display (optional remote keypad).
• Minimum outdoor air and humidity control logic for fresh air intake and optimum humidity levels.
Return or Exhaust Fans
• Return fans can provide better building pressure and ventilation control as return duct pressure drop increases.
• Exhaust fans can save energy as return duct pressure drop requirements decrease.
Factory-Mounted Variable Frequency
Drives
• Control fan motor speed for lower fan operating costs and sound levels in VAV systems.
Airfoil Fans
• More energy efficient and quieter than forward curved fans.
• Double width, double inlet (DWDI) or single width, single inlet (SWSI) plenum fans.
Economizer
• Outside air enters from both sides, improving mixing for better temperature control.
• DesignFlow™ Precision Outdoor Air Measurement and Control System accurately measures and maintains outdoor air quantity.
• Patented UltraSeal™ low leak dampers minimize air leakage, reducing energy costs.
• Generous face area intakes/outlets and control dampers reduce system pressure drops, improving efficiency.
Hinged Access Doors
• On both sides of every section for easy access to all components.
• Single lever latch and door holders provide easy entry and support routine maintenance.
• Double-wall construction protects insulation during maintenance.
Blank Sections
• Available throughout the unit to factory-mount air blenders, carbon or charcoal filters, sound attenuators, humidifiers, or other specialty equipment.
• Allow customization for maximum system performance and efficiency.
• Reduce design and installation costs.
Durable Construction
• Pre-painted exterior cabinet panels pass 750 hour ASTM B117 Salt Spray Test for durability.
• Heavy-duty R-6.5 insulation minimizes heat loss for reduced energy costs.
• Double-wall construction protects insulation and provides a wipe clean surface to inhibit microbial growth.
• Stainless steel, sloped drain pans eliminate standing water and provide long service life.
• Full unit base rail with heavy-duty lifting lugs provide single piece rigging of units up to 150 tons.
Modular Flexibility
• Allows you to specify the unit you want, optimized for high energy efficiency, good IAQ, and quiet operation.
• 100% make-up air, dehumidification, CV, and VAV operation.
• Blow through cooling coil configuration (shown) provides higher sensible cooling, a quiet tenant environment, and energy savings.
• Draw through cooling coil configuration provides higher latent cooling for make-up air systems or systems with high humidity loads.
• Multiple filter, fan, coil, and heating options and sizes to match system requirements.
• Extended face area filters and coils reduce system pressure drops and improve efficiency.
• Multiple high efficiency compressor and coil combinations match system requirements.
• Optional return/supply locations match system configuration requirements at lower installed costs, reduced air pressure drops, and quieter operation.
McQuay’s Unique Features and Benefits
Evaporative Condensing Section
• Open design allows easy access to compressors and refrigerant piping.
• Unique rail support system allows the roof deck and insulation to help block compressor noise from entering the building.
• Replaceable, slide out condenser tube bundles .
• Replaceable, slide out, sectional, sloped stainless steel sump. Heaviest piece weighs less than 175 pounds.
• Entire spray chamber is enclosed in stainless steel.
• Replaceable mist eliminators.
• Replaceable air inlet screens.
• Vertical discharge propeller condenser fans with service guards reduce noise.
• PVC spray system with spray pump, water treatment connections and float control automatically maintains acceptable water levels.
• Replaceable, clog resistant nozzles completely wet the coil surface.
Walk-in Service Compartment
• Ventilation fan with a manual shutter allows conditioned air into the service compartment for comfortable servicing in hot weather.
• Lights, electrical outlet, condensing section electrical panels, spray pump, water connections, and space for water treatment systems and chemical tanks.
• Drain pan under the water piping and a raised floor grate in the pan keeps the walking area dry.
• Single field connections to make-up water and drain lines.
4 Cat 219
Energy Savings
Evaporative Condenser Energy SavingsAir cooled condensers can only reject heat to the ambient dry bulb as the condenser air passes over the condenser surface. Typical design dry bulb temperature is often considered to be 95°F. However, actual rooftop dry bulb conditions are usually much greater due to solar heat on a dark roof. See Figure 1.
Figure 1: Air-Cooled Condenser
Evaporative condensers use a cooling spray of water that evaporates and cools the condenser air down toward the typical ambient wet bulb temperature of 75°F. See Figure 2.
Evaporative condensers, therefore, reject heat to colder temperatures and operate at lower condensing temperatures. Therefore less compressor work and energy are required.
This allows compressors in an evaporative condensing unit to operate at lower condensing temperatures and consume 25-40% less electricity than comparable air cooled units, especially at design conditions. Refer to Table 1.
Figure 2: Evaporative Condenser
Table 1: Air-Cooled vs. Evaporative-Cooled
Condensers
Rooftops with Evaporative Condensers Save Money In Three Ways
1. Savings In Electrical Consumption Costs
Both consumption and demand usually drive the electrical costs for large, non-residential customers. Electrical consumption is the total energy consumed and is usually measured in kW Hours. Several factors influence consumption, including unit efficiency, operating hours, and load profile. McQuay's Energy Analyzer™ computer program is the ideal tool for estimating energy consumption for a given building.
2. Savings in Electrical Demand Costs
Electrical demand is the peak energy consumed in a billing cycle and is usually measured in kW. Demand costs
95/75Air
Heat TransferSurface Cooledby 95°F Air
CondenserSurface
Design Conditions
Ambient Temperature
Condensing Unit kW per ton
Condensing Temperatures
ARI Design Conditions
Air Cooled 95°/ 75°F 1.15 - 1.20 125 - 135° F
Evaporative Cooled
95/75° F 0.84 - 0.88 105 - 115° F
Desert Design Conditions
Air Cooled 110°/72° F 1.35 - 1.40 135 - 145° F
Evaporative Cooled
110°/72° F 0.82 - 0.86 102 - 112° F
Heat Transfer Surface
Cooled by 75°F WB
Within the Spray
CondenserTubes
95/75Air
Cat 219 5
associated with air-cooled and evaporative-cooled rooftops are relatively easy to compare.
a. The 25-40% reduction in peak design condensing unit kW translates into a 25-40% savings in con-densing unit demand costs. Based on utility rate structures, this can be a substantial savings.
b. In addition, McQuay offers airfoil supply and return fans that reduce design BHP and air handler demand costs by up to 20%.
3. Savings in Installation Cost
Rooftop ampacity and electrical service costs are proportional to design KW. A 25-40% reduction in condensing unit design KW translates into smaller and less expensive wires, disconnects and transformers that feed the rooftop units. McQuay's airfoil supply and return fans often save one or two motor sizes and further reduce the required electrical service.
Typical Savings vs. Air-Cooled Rooftop Systems*
To illustrate the savings generated by evaporative condensing, consider a two-story shopping mall using several 125-ton VAV rooftop units and occupied 365 days a year. Assume external static pressures of 2.5" for each supply duct and 0.5" for return ducts. Tables 2 through 4 show the McQuay RPE evaporative condenser rooftop if this mall is located in the Los Angeles, New York and Las Vegas.
Table 2: Comparison of Evaporative and Air-Cooled
Condensing For Los Angeles Area Mall.
* All shopping mall energy analysis and comparison charts pro-
vided in this document have been generated using McQuay
Energy Analyzer™ software.
Table 3: Comparison of Evaporative and Air-Cooled
Condensing For New York Area Mall.
Table 4: Comparison of Evaporative and Air-Cooled
Condensing For the Las Vegas Area
McQuay RPE energy costs are Competitive with any HVAC system - Even Water-Cooled Chillers
Using the 0.85 kW/ton condensing unit efficiency from the previous example, Figure 5 shows a comparison of a McQuay RPE evaporative condenser rooftop system with a 0.55 kW/ton water-cooled chiller system. In this case, we assumed that the chiller system would have constant flow pumps and that it unloads to 0.46 kW/ton.
As shown in Figure 5, the energy performance of the two systems is very comparable, with the RPE offering a significant part load advantage and the chiller offering a small full load advantage. Given that most air-conditioning systems operate at 60% load or less over the great majority of a typical year, the McQuay RPE may be the best energy savings investment.
Table 5: Comparable Energy Performance to Water-Cooled Chillers
McQuay Energy Analyzer is the perfect tool for quantifying the savings that can be generated by evaporative condensing. Energy Analyzer software can model energy consumption for almost any type of building based on local climate and utility costs.
Using Energy Analyzer to Quantify Savings
Go To The Primary System Screen
1. Click On The Condensing Unit
2. Click On Air Cooled Or Evap Cooled
3. Check The Defaults
For access to McQuay Energy Analyzer Software, contact your local McQuay representative for a copy. To locate your McQuay representative, visit mcquay.com or call (800) 432-1342.
Energy Analyzer - Primary System Screen
1 13
2
Cat 219 7
FeaturesMcQuay RPE and RDE units contain the same air handler construction and controls as McQuay RPS and RDT applied rooftop units. For more detail, refer to RPS Catalog 214 and RDT Catalog 217. For a copy of these catalogs, contact your local McQuay representative or visit mcquay.com.
Refrigeration Circuit
• Open condenser design allows easy service access to compressors and refrigerant piping.
• Multiple high efficiency Copeland Discusá compressors mounted on isolators with crankcase heaters, positive displacement oil pump, low oil pressure protection control, 3-leg internal motor protection and cylinder unloaders for up to 8 steps of capacity control.
• Dual refrigerant circuits include manual shut off valves on the suction, discharge and liquid lines, accessible sight glass, filter drier and solenoid valves (expansion valves are included in the air handler section). The controls include high and low refrigerant pressure protection control switches, manual control switch, and manual pump down switch.
• Compressors are allowed to operate down to 45° F ambient, where economizer ‘free cooling’ operation takes over.
Evaporative Condenser
• Unique rail support system allows the roof deck and insulation to help block compressor noise from entering the building.
• Replaceable, slide out condenser tube bundles are constructed of corrosion-resistant copper tubes, stainless steel casing, and polymer tube sheets.
• The sloped, stainless steel sump is divided into multiple sections that slide out for easy replacement. The heaviest section weighs less than 174 pounds.
• The entire spray chamber is constructed of corrosion-resistant stainless steel.
• Replaceable mist eliminators between the tube bundle and condenser fans minimize water consumption.
• Replaceable air inlet screens keep sunlight out of the sump and help prevent microbial growth.
• Direct drive condenser fans eliminate the service expense associated with belts and sheaves.
• Vertical discharge, propeller condenser fans with service guards reduce horizontal-radiated noise.
• 3-phase, severe duty, totally enclosed condenser fan motors with current sensing overload protection and permanently lubricated bearings support extended product life.
• PVC spray system includes spray pump, water treatment connections and float control that automatically maintains acceptable water levels. Replaceable, clog resistant nozzles spray water across a 150° arc and completely wet the coil surface for improved performance. Single field connections to make-up water and drain lines can reduce installed cost.
Figure 3: Standard RPE and RDE Spray System (See Figure 4 on page 12 for Water Treatment Enhancements)
Water TreatmentConnections
Manual Bleed OffSolenoid Valve
Manual Shut Off Valve
To SanitarySewer
RemovableScreen
Pump
Sump
Automatic Float ControlledIntake Valve
Hose Bib withManual Shut OffValve
Intake Water
Spray
8 Cat 219
Corrosion Resistant
Easy Service Access
Walk-in Service Compartment
• All routine refrigerant service can be performed inside the walk-in service compartment away from compressor noise and outdoor conditions.
• Contains marine lights, electrical outlet, condensing section electrical panels, spray pump, water connections, and space for water treatment system and chemical tanks.
• A thermostat-controlled ventilation fan turns on at 75°F and a manual shutter draws conditioned air into the service compartment for comfort. These features provide more comfort for service even in hot weather.
• A hose bib is provided as standard in the make up water line to aid in condenser cleaning.
• A drain pan under the water piping and a raised floor grate in the pan help keep the walking area dry.
• Optional unit heater for cold climate use.
• No compressor noise is generated in the work area.
• Sight glass, filter driers, solenoid valves and charging valves are in the service compartment.
Walk-In Service Compartment
Stainless Steel Spray Enclosure
PVC
Spray
Tubes
Stainless
Steel Sump
Copper
Tube Bundles
Polymer Tube Sheets
Stainless Steel Fan Decks with
Severe Duty Motors and
Corrosion-Resistant Fans
Walk In
Service
Compartment
Access Doors
on Both Sides
Replaceable Nozzles
with 150° Spray Arc
Replaceable, Slide Out
Tube Bundles
Replaceable
Sump
Easy
Compressor
Access
Access to Most
Electrical Components
Perform Most Refrigerant Service in Comfort, Away From Compressor Noise
Raised Floor Grate and Drain Pan
Charging, Suction,
Discharge & Liquid
Schrader Connections
Solenoid, Sight Glass
& Filter Drier
Hot Gas
Bypass
Valves
Space for
Water
Treatment
Marine Lights Exhaust Fan
Optional Unit
Heater
Cat 219 9
Cabinet
• Weather resistant skin is made of pre-painted, galvanized steel that successfully withstands a 750 hour salt spray test. The service compartment walls are double wall with R6.5 insulation sandwiched between the outer skin and inner liner. The air handler cabinet is also available with double-wall construction with R6.5 insulation.
• Full-sized, double-wall, hinged access doors are provided on each side of the section, complete with a single lever latch.
• Heavy gauge galvanized steel base with a formed recess sits on the gasketed curb and provides a weather tight seal. The base also includes strategically placed lifting brackets to allow balanced cable or chain hook lifting.
Air Handling Section
• Factory piped, charged and tested refrigeration system comes complete with an aluminum fin, copper tube, DX coil with expansion valves and distributors. Each distributor tube is wrapped in plastic to help prevent refrigerant leaks.
• DX coils feature interlaced circuiting to keep the entire coil face active during all capacity steps and eliminate the air bypass associated with face split coil designs. An intermediate drain pan collects condensate from the top half of the coil. Drain tubes run from the intermediate drain pan to the sloped, galvanized [optional stainless] steel drain pan.
• High efficiency airfoil supply fans require less BHP and generate less noise than forward curved fans at the medium static pressures typical of large VAV units. Fans are available in both DWDI (housed) and SWSI (plenum) fan arrangements. For more information, refer to page 14 through 16.
• Insulated supply and return air plenums with bottom [optional horizontal] openings reduce ducted noise levels. A double wall option is available with perforated liners in these sections
Airfoil Fans
Electrical and Controls
• Single source power with optional, non-fused disconnect switch with control panel door interlock.
• Individual short circuit protection for each compressor, supply fan and return fan motor. Condenser fan and exhaust fan motors are also provided with short circuit protection.
• All control panel wiring is labeled per the wiring diagram and all 115-575 volt wiring is housed in conduit or metal raceways.
• MicroTech II™ control system with state of the art control sequences communicates with BAS systems through Protocol Selectability™. This allows any building automation system (BAS) to communicate with MicroTech II over an industry standard network and obtain access to the operating status, all set points, and alarms.
• LONMARKá certified discharge air control (DAC) or space comfort control (SCC) communication options.
• BACnetá compliant communication options.
• MicroTech II is available in several temperature control modes.
• LONMARKá certified Space Comfort Control [SCC] for single zone, constant volume applications; including 100% make-up air application.
• LONMARKá certified Discharge air temperature control [DAC] for VAV or constant volume applications. Static pressure control of the supply fan and return/ exhaust fan can also be included.
• Time clock, lead lag, morning warm up, night set back, economizer pre-cool and flexible reset are all standard.
• Published integration instructions for both forms of communication.
• Unit mounted keypad and 4-line by 20-character display provide an enhanced user interface.
• Compressor head pressure control that reliably cycles the condenser fans from sump temperature down to 45° F ambient.
• Duct high pressure safety on all VAV units.
MicroTech II Keyboard
10 Cat 219
Factory Installed and Wired OptionsThe RPE and RDE contain the same air handler construction and controls as the RPS and RDT units. For complete detail refer to RPS Catalog 214 and RDT Catalog 217. For a copy of these catalogs, contact your local McQuay representative or visit mcquay.com.
Condensing Section
• Compressor spring isolation with suction and discharge line vibration absorbers.
• Extra compressor unloaders that provide 6 stages (size 76-100) or 8 stages (size 110-150) of capacity control.
• Compressor part winding start to reduce inrush current.
• Replaceable core filter driers.
• Hot gas bypass on one or both refrigerant circuits.
• Electric sump heater that helps prevent the sump from freezing in cold weather. Heat tape is also included for the sump drain and supply water lines.
• 1.5 kW electric unit heater and ambient on-off thermostat for the service compartment
Air Handling Section
• Multiple fan and coil options optimize reliability, efficiency, sound performance and first cost for varying CFM per ton operation. Units can be selected for make-up air applications.
• Economizer systems come standard with outdoor and return air damper leakage rates of less than 0.5% at 1.5" static pressure. Economizers are available with the following value add options.
• Patented DesignFlow™ minimum outdoor air measurement and control system that is independently certified to control ventilation air within +/- 5% of set point from 1,594 to 37,126 CFM of outdoor air.
• Static air mixers that provide optimum uniformity in mixed air temperature and reduce the chances of freezestat trips and localized coil freezing.
DesignFlow™
• Economizers are available with return fans or exhaust fans.
• SWSI airfoil return fans provide better building pressure and ventilation control on ducted returns.
• Multiple propeller exhaust fans may save energy on low-pressure drop, ceiling plenum returns.
• see “Economizer, Return Fan and Exhaust Fan Application” on page 15.
• Variable frequency RAF and SAF drives for VAV control (exhaust fans always include a variable frequency drive).
• Supply and return fan belt guards.
• Spring isolation (with optional seismic construction).
• Cooling coils are available in blow through and draw through arrangements to optimize the use of fan and motor heat. See Figure 12 on page 18.
• In blow through arrangements (RPE only), fan energy pre-heats the mixed air temperature before entering the cooling coil, providing greater sensible capacity and colder supply air temperature for a given compressor capacity.
• In draw through units, fan energy re-heats the air leaving the cooling coil. Draw through systems provide greater latent cooling capacity, lower sensible heat ratios.
• Gas and electric heat are available on RPE units with the following options.
• Two-pass drum and tube heat exchanger with, fully modulating, FM approved burners for 3 to 1 or 20 to 1 (patented SuperMod™) turn down and optional IRI approval. Drum and tube heat exchangers feature all stainless steel construction. Selections are available to handle up to 100°F temperature rise.
• Low watt density, nickel chromium electric heaters with branch short circuit, automatic reset and manual reset safety.
• 1- or 2-row hot water or jet distributing steam coils with optional valve control and optional freezestats.
• Supply fan sound attenuators with or without mylar coating of the acoustic insulation (RPE only).
• Generous face area, 2" pleated, 30% efficient panel filters and/or 65 or 95% cartridge filters are available Cartridge filters can be in the final, last in air flow position for hospital or laboratory applications (RPE only).
• Blank sections can be added for field-installed devices such as humidifiers and integral face and bypass coils.
• Ultraviolet Germicidal Irradiation (UVGI) lamps are available factory installed in all RDE/RPE units to cleanse cooling coils and drain pans. The UVGI lamps irradiate the cooling coil and drain pan surfaces with light in the 254-nanometer wavelength of the light spectrum (UV-C). UV-C light has been proved effective in killing most bacteria, molds and viruses in both laboratory and practical application. In addition, the continuous “cleansing” action of the UV-C light also serves to continuously clean the coil and drain pan, improving long-term performance and reducing coil/drain pan maintenance. The completed package of McQuay equipment and UVGI lights includes Intertek Services Inc. (ETL) safety agency certification.
Cat 219 11
Electrical and Controls
• Smoke detectors in the supply and/or return air openings.
• Marine lights in the supply and/or return/exhaust fan sections.
McQuay MictroTech II™ Rooftop Remote User Interface
Each remote user interface is identical to its unit-mounted counterpart and offers the same functionality, including:
• Touch sensitive key pad with a 4 line by 20 character display format.
• Digital display of messages in English language.
• All operating conditions, system alarms, control parameters and schedules are monitored.
Features
• Can be wired up to 1,200 feet from unit for flexibility in placing each remote user interface within your building.
• Unit-mounted switch enables the remote user interface during normal operation or the unit user interface for maintenance and service.
Benefits
• Allows you to access the user interface for each unit from one location, inside the building.
• Users need to learn one format because the remote user interface is identical to the unit-mounted version.
McQuay MicroTech II™ Multiple Air Handler Control (MAC)
The MAC provides control coordination for multiple Rooftops serving a common space or feeding a common ductwork system.
The MAC manages each group of units to operate in concert. Individual unit controls cannot reliably handle parallel units because the controls fight each other at part load. Inevitably one unit overpowers the other.
Benefits of Parallel Units on a Common Duct
• Improved system reliability as units and sensors can provide redundancy if a sensor or unit require maintenance.
• Lower first cost from increased diversity resulting in lower installed tonnage.
• Lower installed cost due to fewer roof penetrations and less floor-to-floor ductwork.
• Improved space temperature control from smaller cooling stages relative to load and reduced compressor cycling.
Field-Installed Roof Curbs
• Constructed in accordance with NRCA guidelines using 12-gauge galvanized steel.
• Fits inside the unit base around the perimeter of the air handling section and service compartment.
• Duct frames are provided to allow duct connections to be made to the curb before the unit is placed. The unit seals to the duct frames.
• Ship loose gasket seals between the unit and curb.
• Separate condensing unit support rail allows an open condensing unit design and minimizes compressor noise and vibration transmission through the roof.
Common
Supply Duct
MAC Panel
Remotely
Mounted
IndoorsCommon
Return Duct
12 Cat 219
Optional Water TreatmentAll evaporative condensing products require water treatment systems for proper operation. The water treatment system serves the following purposes:
• Controls organic contamination
• Reduces condenser fouling and corrosion
• Reduces cleaning frequency and water usage
Overview
McQuay RPE/ RDE units come with a spray system, pump, sump strainer, automatic float controlled intake, and manual bleed off as standard.
McQuay offers a basic water treatment option that includes the following factory-installed features:
• Controlled bleed off
• Digital controller and sensors
• Combination corrosion and scale inhibitor, chemical tanks and feed system
• Biocide chemical tank and feed system
If the McQuay basic water treatment option is not purchased, then an equal system must be field installed (manual bleed off is not recommended).
The following water treatment enhancements are offered for more severe applications.
• Intake and bleed off, water meters
• Side stream cyclone separator
• Corrosion sensing coupons
Bleed Off and Water Consumption
Controlled bleed off [or blow down] is required on McQuay RPE/ RDE units as it should be with all evaporative condensing products. It involves draining off a portion of the highly concentrated water from the bottom of the sump and replacing it with lower concentration make-up water to prevent scale. Scale protection is required because the evaporation process leaves behind solids (scale) that will coat the heat exchanger surfaces and sump. This reduces the capacity, efficiency, and life expectancy of the equipment.
Manual bleed off occurs whenever the spray pump operates and a manual valve adjusts flow. This inevitably bleeds off too much [increased water costs] or too little [risking scale build up] water. Controlled bleed off is included with the McQuay water treatment controller. The concentration of scale forming solids is measured by water conductivity and the control opens or closes a solenoid to allow the proper amount of bleed off. The conductivity set point should be adjusted based on water analysis to maintain a desired cycles of concentration.
Figure 4: McQuay Water Treatment Option
Bromine
Corrosion& ScaleInhibitor
Controllerwith 3Sensorsto ControlBothSolenoids
Flow
Conductivity
ORP
OptionalInternetConnectionDrain Solenoids
(not shown) openduring freezingconditions
Optional Water Meters
Corrosion Sensors
M
M
M
CS
CS
OptionalCycloneSeparator
HandValve
ControlSolenoid
Automatic Bleed OffSolenoid Valve
To SanitarySewer
PumpIntake Water
Spray
RemovableScreen
SumpSump
Automatic Float ControlledIntake Valve
Hose Bib withManual Shut OffValve
Cat 219 13
Theoretical water consumption required for proper heat rejection is 1.8 gallons per ton hour. All of this water evaporates and none goes into the sewer. An additional 0.6 to 0.9 gallons per ton hour is also required for make up and bleed off. The exact amount should be determined by water analysis. The RPE/ RDE includes a float valve and solenoid that automatically refills the sump as required.
Bleed off must be handled in accordance with local codes and normally is drained into the sanitary sewer. This water should never be drained onto the roof or into a storm drain. Because most water utilities charge for both intake and sewer water flows based on intake meter readings, sewer charges may be reduced if sewer flow is proven to be less than water intake. McQuay offers both intake and bleed off water meters to document reduced sewer flow [confirm details with your local utility]. These meters are not included in the basic water treatment option.
Particle Control
Particle filtration is required to remove dirt and debris that collects in the spray water. A large face area sump strainer is included in the sump drain that prevents debris from entering the pump and spray system. The sump strainer can easily be removed and cleaned. A hose connection is included, upstream of the float valve, so that sludge can be washed out of the sump as needed.
For areas where airborne dirt and debris are more severe, a side stream cyclone separator can be added when the McQuay water treatment control is purchased. About 10% of the flow is diverted to the separator. Collected particles are purged in conjunction with controlled bleed off that is included in the McQuay water treatment controller.
Figure 5: Figure - Centrifugal Solids Separator
Controller and Chemical Treatment
The McQuay water treatment option includes a controller, sensors, chemical feed equipment, interconnecting piping, and control wiring. The McQuay water treatment option can be enhanced to simplify its operation and the supply of chemicals for your RPE or RDE unit.
• Water analysis is available to allow optimum setting of controller set points, water bleed off rates, and chemical feed rates.
• Chemicals can be ordered and shipped to the job site.
• An optional Internet card for field Internet connection is available to support 24/7 remote monitoring of chemical levels and water quality. Consult you local McQuay Representative for contact information.
• Precisely selected and weighed metals (corrosion coupons) can be placed in the spray water. The weight reduction of these coupons over time is measured to reveal corrosion problems before they are severe.
The spray systems use only PVC, copper and stainless steel materials, but corrosion can occur if proper water treatment is not provided. McQuay offers a chemical treatment system with a combination scale and corrosion inhibitor that increases the water solubility limits, helps protect against scale, reduces bleed off water requirements and helps protect the system metals from corrosion. The inhibitor treatment products do not simply dissolve. The products are encapsulated in a proprietary coating that allows the chemistry to diffuse into the system water. This diffusion rate is highly predictable and the release rate is constant over a 33 “operating” day period as long as the product is in water. Chemical treatment demand for the “operating” period is calculated based on water quality which determines the amount of chemicals to be added.
Figure 6: Dry Chemical Injection System
Microbial protection is required to help prevent heat exchanger and spray system fouling and corrosion. The McQuay Controller meters dry chemicals [such as bromine] into the spray water through a solenoid to maintain sufficient oxidation-reduction potential [ORP] and kill microorganisms. Bromine is recommended because it is easy to handle and microorganisms do not develop immunity to oxidizing biocides.
14 Cat 219
Application ConsiderationsThe RPE and RDE require many of the same application considerations as McQuay RPS and RDT units. More detail is provided on pages 11-12 and 23-29 in RPS Catalog 214-5 and RDT Catalog 217-5. For a copy of these catalogs, contact your local McQuay representative or visit mcquay.com
General• Intended for normal HVAC use. Consult factory if
cataloged operating range is exceeded, such as make up air. Compressor cooling below 45° F is not allowed.
• Rig the unit in accordance with the instructions provided in the Installation Manual IM-791. Split units are available to reduce rigging weight and may be required if the total length exceeds 52 ft. For a copy of IM-791, contact your local McQuay representative or visit mcquay.com.
• Fire dampers may be required by code. They are not included.
• Qualified Start up of the unit in accordance with the IM-791 is required.
• Clean off any road chemicals, such as winter salt, when the unit is received.
• Proper water treatment must be provided before unit start-up.
Location and Curb/ Rail Support• The structural engineer must verify that sufficient roof
strength is provided.
• Maximum unit pitch is 1/16 in. per foot. Curbs or supporting rails must be rigidly supported along the entire length of the unit to prevent deflection that results in door interference.
• Gaskets must be installed between the curb and the unit, per IM-791.
• Curbs must be installed per NRCA guidelines. see “Roof Curbs” on page 48.
• Avoid locating the unit near any heat source, exhaust, smoke stack, or any source of air-borne particles or chemicals.
• Local codes must be followed regarding fastening the unit to the curb/ rail and the curb/ rail to the building. This is especially critical in higher risk, hurricane or seismic zones.
• Refer to the “Acoustics” section below to avoid noise and vibration problems.
• McQuay curbs include supply and return opening support frames and perimeter channels that seal to the unit as it is placed on the curb. Therefore, duct connections can be made to the curb before the unit is placed.
Acoustics Ducted and radiated sound power ratings are available from your local McQuay sales representative. The designer is responsible for addressing these sound levels.
The following guidelines will help to achieve the desired sound levels in the occupied space.
• Locate the unit as far away from sound sensitive areas as possible. Refer to the “Location and Curb/ Rail Support” section.
• Minimize supply and return fan TSP and select the fan as close to peak efficiency as possible. Avoid the “do not select” areas on the fan curve. McQuay offers several different fans per model size to allow for various design conditions. Refer to “Fan Performance Data” on page 38.
3 different sound paths from the unit to occupants and/or neighbors must be considered.
1. Radiated Path
• Use a concrete deck or pad when the unit must be located over sound sensitive areas. If this isn't possible, provide extra acoustical insulation under the condensing unit.
• Only the supply and return ducts, and the essential plumbing and electrical connections should penetrate the acoustical insulation or roofing below the unit. The outside perimeter of the ducts must be sealed after they are installed.
• If a built-up roof with metal decking is used, then the area inside the curb perimeter requires special attention:
• Provide an inverted 6" channel around the inside perimeter of the curb and seal to the curb.
• Acoustical insulation must be installed above the decking and the 6" channel.
2. Vibration Path
• Locate the unit's center of gravity close to a main support beam to minimize roof deflection and vibration transmission into the building.
• McQuay offers 2" deflection, supply and return fan spring isolation or rubber in shear isolators. The rubber in shear isolators should only be used when vibration isolation is clearly not required in the rooftop, such as when the unit is mounted on spring isolated curbs, spring isolated rails or the ground.
• McQuay offers compressor spring isolation, including the necessary refrigerant line vibration eliminators.
• Internal spring isolation options may be insufficient for some applications. Spring isolation of the entire unit may be required.
3. Air-borne path through the supply and return openings
• Use 2003 ASHRAE Fundamentals Chapter 43 to help reduce ducted noise and minimize duct turbulence. Maintain straight ducts to and from the unit and avoid abrupt changes in duct size and direction. Avoid turns opposed to the fan wheel rotation. If 90° elbows are required, use turning vanes.
• Use as much insulated return duct as possible and include at least one elbow and 15' of length. Maximum recommended velocities are 1000-1200 fpm.
• Allow for duct break out and use oval or round duct whenever possible.
Cat 219 15
• Insulate the first 20' of supply duct. The first 20' of rectangular duct should be routed over non-sensitive areas and avoid large aspect ratios. Maximum recommended velocities are 1800-2000 fpm.
• McQuay offers factory-installed discharge plenums with optional perforated liners. The plenum provides several dB of attenuation and discharges the air at a more uniform, relatively low velocity. Ducted supply noise can be further reduced by adding optional sound attenuators between the supply fan and the unit discharge.
• Route the return air path through the length of the curb to add distance between the unit return opening and the building return opening.
Economizer, Return Fan and Exhaust Fan ApplicationRooftop economizer applications usually require return or exhaust fans to properly control building pressure and maintain minimum ventilation. McQuay offers both exhaust and return fan capability. They are not generally interchangeable for a given design. In general:
• Return air fans (RAF) should be used on ducted return systems [return ESP exceeds 0.4 - 0.5 in.]
• Properly selected propeller exhaust air fans (EAF) can successfully operate and save energy on open return systems [return ESP is less than 0.4 - 0.5 in.]
• Supply air fan (SAF) selection depends on whether a return or exhaust fan is used.
• RAF system-SAF handles only the supply ESP at design.
• EAF system-SAF handles both the supply and return ESP at design [EAF is off.]
Figure 7 illustrates why supply fan only units have problems, especially as return ESP increases.
• No exhaust will occur from the rooftop because the economizer section must be at a negative pressure.
• The air balancer must adjust the outdoor air damper to generate large pressure drops at minimum ventilation settings [about 0.9" in Figure 7.]
Figure 7: Supply Air Fan Only System Static
Pressures with 1” Return Duct ESP
Figure 8 illustrates how the addition of a return fan corrects these problems. The return fan is responsible for return system ESP and maintains a slightly positive pressure in the economizer section [about +0.1 in. in
Figure 8.] to allow for exhaust air control and a more suitable outside air intake pressure.
Figure 8: RAF System Allows Proper Exhaust and
Outdoor Air Control
Exhaust fans are very different than return fans and can not maintain proper building pressure and ventilation control as return ESP increases.
• Exhaust fan systems are intended to save energy by having the fan 'off' during non-economizer operation. During these minimum outdoor air conditions, the system essentially acts like a supply fan only system.
• With the exhaust fan off, there is no device available to maintain a positive pressure for relief, the mixed air plenum goes to an accentuated negative pressure condition affecting minimum ventilation air control and space pressure is no longer under control.
An exhaust fan's performance weaknesses diminish as return ESP decreases. Properly selected and controlled propeller exhaust fans can successfully operate and save energy at reduced return ESP designs.
• At system operating conditions where a single fan can be used successfully, it generally will be more efficient than operating series fans under the same total load. When the exhaust fan turns off, the supply fan can efficiently handle both the supply and return duct loads.
• At the relatively high CFM, low static pressure conditions of exhaust/return application, exhaust fans can be selected closer to their peak design efficiency than can full return fans. This allows them to run more efficiently throughout their operating range. Therefore, when return duct losses don't dictate the use of a return air fan, exhaust fans are an efficient alternate.
Filters• Filters should be replaced on a regular basis to avoid
excessive pressure drop increases, especially on high efficiency cartridge filters.
• Fan selection must consider dirty filter losses. Using a filter pressure drop midway between clean and dirty values is recommended unless maintaining minimum CFM is critical.
• McQuay RPE units offer last in air stream “final” filters. They require special consideration.
• The McQuay design uses full double wall construction down stream of the final filters.
• Cooling coils must be in the draw through position.
• Final filters down stream of gas and electric heaters must be rated for 500° F temperatures. Maintenance personnel must use properly-rated replacement filters.
Variable Air Volume (VAV)McQuay Rooftop VAV options include everything required to provide the full advantages of true shut-off VAV. Bypass VAV systems do not offer any fan energy savings at light load.
• Variable Frequency Drives for all indoor fans maximize part load fan efficiency and minimize fan sound generation.
• Indoor fan volume control based on supply static pressure and building pressure.
• Up to 2 supply duct sensors to properly respond to building diversity (such as east-west variation).
• Constant discharge temperature control.
Shut-off VAV offers the following advantages.
• Reduces first cost and energy due to building diversity.
• Reduces indoor fan energy requirements at light load.
• Provides the opportunity for efficient multiple zone control from a single unit and to match changing occupancy demands.
• VFDs turn down in accordance with Figure 9.
Figure 9: VFD Turndown
The benefits of McQuay airfoil fans are particularly applicable to VAV applications.
• Better efficiency and less noise at the medium static pressures associated with VAV.
• Airfoil fans are much more forgiving than forward curved fans if unexpected variations in ESP occur.
• They are “non-overloading” (BHP is fairly constant for a given RPM) and require less safety factor in motor selection.
• They have steeper RPM lines (less variation in CFM for a given variation in ESP).
• Multiple forward curved fans are often used and they risk unstable fan paralleling at light load.
MicroTech II™ controlSupply fans are controlled to maintain constant supply duct static pressure.
• Run pressure-sensing tubes to the desired location (generally at the end of the main trunk).
• Use a second sensor when there is more than one main trunk, multiple floors, or significantly varying zones (such as east and west sides of a building).
Return / exhaust fans are controlled to maintain building pressure in one of two ways.
• McQuay's exclusive Vanetrol™ supply/return fan tracking is generally preferred. Vanetrol is adjusted at system air balance to maintain proper building pressure throughout the expected loading conditions. This reduces the effect of wind, climate variation and doors opening and closing.
• Direct building sensing control is available for exhaust fans or any return fan application that cannot predictably track the supply fan.
McQuay generally offers more steps of compressor capacity control than the industry norm, as well as HGBP, and these capabilities should be included on VAV applications to minimize variations in duct temperature.
Unit Operating Range (CFM and Temperature)
Fan Operating Range
The acceptable system operating range of the McQuay rooftop unit is determined by all of the following characteristics. Each of these limiting factors must be considered for proper performance and component design life.
1. Unstable fan operation
2. Maximum fan rpm
3. Maximum cabinet static pressure
4. Maximum face velocity (cooling coil is most important)
5. Minimum furnace or electric heater velocity
6. Turndown capability on VAV applications
7. Compressor operating pressures
Figure 10 on page 17 illustrates these limiting factors with the exception of items 6 and 7. The shaded area indicates the design operating range of the fan. For optimal efficiency, select fans as close to the fan’s peak static efficiency line as possible. This line is the first system curve to the right of the unstable line illustrated. VAV fan selections must also allow for keeping the fan away from the “do not select” area at minimum design CFM.
Cat 219 17
Figure 10: Fan Selection Boundary
Cooling coil maximum face velocity is based on moisture blow off limitations and laboratory testing.
• 650 feet per minute maximum face velocity for 8 and 10 fin per inch coils.
• 600 feet per minute maximum face velocity for 12 fin per inch coils.
• Cooling coil minimum face velocity is 200 feet per minute for any coil selection. VAV systems must be designed such that this velocity is maintained at minimum airflow.
• Maximum design ambient wet bulb temperature varies per unit, but is at least 85° F. Evaporative condenser units are an excellent choice for high ambient applications.
• The minimum ambient temperature for compressor operation is 45° F. The MicroTech II™ Controller is set to prevent compressor operation below that temperature and use the economizer only when cooling is required at a lower ambient.
Indoor Fan and Motor Heat, Blow Through versus Draw Through Cooling
Indoor fan and motor heat.
• The indoor fan and motor electrical consumption is a sensible cooling load approximately equal to 2.8 MBH per BHP (depending slightly on motor efficiency). This occurs at the fan. See Figure 11 and Figure 12. The fan and motor preheat the mixed air before it enters a blow through cooling coil. The fan and motor reheat the air leaving a draw through cooling coil. Refer also to 2001 ASHRAE Fundamentals Handbook, Chapter 31.
• Fan and motor temperature rise is equal to BTUH / (1.08 x CFM) and is typically about 3° F.
• Due to fan and motor heat placement (Figure 11), blow through coils provide a high sensible heat ratio while draw through coils provide more latent cooling per total ton. Blow through coils achieve a higher sensible heat ratio because they operate with a higher coil approach temperature and a lower entering relative humidity. Conversely, draw through coils cool air at a lower approach temperature and a higher relative humidity, increasing latent cooling.
• Blow through coils effectively provide colder supply air temperatures per ton of air conditioning and
greater sensible heat ratio. This potentially allows a significant reduction in design CFM for buildings with high sensible heat ratios and a resulting reduction in building energy use.
Figure 11: Blow Through vs. Draw Through Concept
Min Furnace,Electric Heat,
or DX Coil Airflow
Max CabinetStatic Pressure
Max RPM
Uns
tabl
e Li
ne
Pea
k St
atic
Effi
cien
cyMax FaceVelocity
Do Not Select
Draw Through Cooling Design
Blow Through Cooling Design
Fan & Motor Heat After Coil
Fan & Motor Heat Before Coil
Fan
Fan
DXCoil
DXCoil
18 Cat 219
Figure 12: Blow Through and Draw Through Performance Comparison
Recommended Clearances
Service Clearance
Allow the recommended service clearances shown in Figure 13. Provide a roof walkway along two sides of the unit for service and access to most controls.
Cooling coil, heat and supply fan service clearance
An additional clearance of 24” is recommended adjacent to the cooling coil, heat, and supply fan sections.
Figure 13: Service Clearances
3° D.T.
Reheat
MAT
3° B.T.
Preheat
Coil EAT Is
DifferentCoil LAT Is
Different
Roof Walkway
24"
72" Service Clearance on4 sides except as indicated
72" Clearance toend of unit or endof outside hood
Adjacent to Cooling Coil, Heat, and Supply Fan Sections.
Cat 219 19
Overhead Clearance
1. Unit(s) surrounded by screens or solid walls must have no overhead obstructions over any part of the unit.
2. The area above the condenser must be unobstructed in all installations to allow vertical air discharge.
3. The following restrictions must be observed for overhead obstructions above the air handler section:a. There must be no overhead obstructions above the
furnace flue, or within 9 inches of the flue box.b. Any overhead obstruction shall not be within 2
inches of the top of the unit.c. A service canopy must not protrude more than 24
inches beyond the unit in the area of the outside air and exhaust dampers.
d. Flue box outlet must extend above any obstructions.
Outdoor Air Intakes
Do not locate outside air intakes near exhaust vents or other sources of contaminated air.
If the unit is installed where windy conditions are common, install wind screens around the unit, maintaining the
clearances specified. This is particularly important to prevent blowing snow from entering outside air intakes.
Ventilation Clearance
Unit(s) surrounded by a screen or a 50% open area fence:
1. The bottom of the screen should be a minimum of 1 ft. above the roof surface.
2. Minimum distance from the unit to screen is the same as the recommended service clearance.
3. Minimum distance, unit to unit - 120 in.
Unit(s) surrounded by solid walls:
1. Minimum distance from the unit to the wall is 96 inches for all sizes.
2. Minimum distance from the unit to another unit is 120 inches.
3. Wall height restrictions:a. No restrictions if there is a wall on one side only, or
on two adjacent sides.b. The wall height is restricted to no more than the unit
height with walls on more than two adjacent sides.
Figure 14: Ventilation Clearances
Maximum AllowableOverhead Canopy Area
9" Min to Flue BoxTypical All Sides
Flue Box
24" Max
24" Max
2" Top of UnitTo OverheadObstruction
20 Cat 219
Control and Power WiringWiring must be done in accordance with the NEC and local code. For wire sizing instructions, see “Supply Power Wiring” on page 53.
• All units require 208-60-3, 230-60-3, 460-60-3, 575-60-3 or 380-50-3 power.
• Size wire in accordance with tables 310-16 or 310-19 of the National Electric Code. Wires should be sized for a maximum 3% voltage drop. Copper conductors must be used.
• Actual voltage at the unit connection must be within +/- 10% of nameplate voltage at all times.
• McQuay offers several power connection options.
• Single power connection with a terminal block or non-fused disconnect are normally the most economical.
• Systems served by emergency generators often require two power connections (with terminal blocks or non-fused disconnects). The generator normally serves only the air handler and controls portion so the condensing unit must be powered separately.
• Each unit is provided with a separate 115-volt convenience outlet that requires a separate power connection per the NEC.
• A second, 115 volt power supply is required to power the optional unit heater for the service compartment.
Most units require a zone temperature sensor for night heat and other functions. The sensor must be properly placed so that its temperature reflects the zone requirements. Avoid outside walls, sunlight and close proximity to supply air or heat generating equipment. A return air sensor can be substituted for the space sensor if necessary.
Altitude AdjustmentsFan curve performance is based on 70°F air temperature and sea level elevation. Selections at any other conditions require the following adjustment for air densities listed in Table 6 on page 20. Higher elevations generally require more RPM to provide a given static pressure but less BHP due to the decrease in air density.
1. Assume 32,000 CFM is required at 3.11” TSP. The elevation is 5000 ft. and 70°F average air temperature is selected. A 40” DWDI airfoil fan is selected.
2. The density adjustment factor for 5000 ft. and 70°F is 0.83.
3. TSP must be adjusted as follows; 3.11” / 0.83 = 3.75”
4. Locate 32,000 CFM and 3.75 on the fan curve. RPM = 900 and BHP = 27.5. The required fan speed is 900 RPM.
5. The consumed fan power at design = 27.5 BHP x 0.83 = 22.8 BHP.
Figure 15: RPE 105C-135C 40 in. DWDI Airfoil
Table 6: Temperature and Altitude Conversion Factors
Air Temp (°F)
Altitude (Feet)
0 1000 2000 3000 4000 5000 6000 7000 8000
-20 1.20 1.16 1.12 1.08 1.04 1.00 0.97 0.93 0.89
0 1.15 1.10 1.08 1.02 0.99 0.95 0.92 0.88 0.85
20 1.11 1.06 1.02 .098 0.95 0.92 0.88 0.85 0.82
40 1.06 1.02 0.98 0.94 0.91 0.88 0.84 0.81 0.78
60 1.02 0.98 0.94 0.91 0.88 0.85 0.81 0.79 0.76
70 1.00 0.96 0.93 0.89 0.86 0.83 0.80 0.77 0.74
80 0.98 0.94 0.91 0.88 0.84 0.81 0.78 0.75 0.72
100 0.94 0.91 0.88 0.84 0.81 0.78 0.75 0.72 0.70
120 0.92 0.88 0.85 0.81 0.78 0.76 0.72 0.70 0.67
Cat 219 21
Freezing ConcernsFreeze protection measures must be taken for any rooftop exposed to freezing conditions. The owner and building designer must take primary responsibility based on the exact climate and installation conditions.
• Drain all condenser water as soon as the climate allows the economizer to provide all required cooling.
• The optional sump heater is recommended to protect the sump if ambient temperatures can drop to freezing conditions (even at night).
Spray system
The spray tree and nozzles are not vulnerable to freezing because water drains out of them when the spray pump is off. Remove the sump drain plug whenever the unit is not in operation to prevent precipitation from building up in the sump and drain.
Two freeze protection options are required to prevent the rest of the spray system from freezing.
1. An optional service vestibule heater provides primary freeze protection of the spray system enclosed in the vestibule. A thermostat turns the unit heater on when vestibule temperature drops to 40°F.
2. A sump heater is a recommended option that includes the following:
• An ambient thermostat-controlled insertion heater for the sump.
• Heat tape, insulation and thermostat for the sump drain.
• Heat tape, thermostat and insulation is included on the high pressure, factory water inlet piping upstream of the float control valve. An additional 10 feet of heat tape is provided to protect field connections. The installer must provide additional heat tape as required and insulate all field piping.
• An emergency drain solenoid opens up whenever the vestibule temperature drops near freezing and the spray system drains onto the roof.
Hot Water and Steam Coils
The RPE/RDE economizer offers better mixing capability than competitive rooftops but it cannot protect a hydronic coil from localized freezing. Optional air mixers are available to reduce air stratification and freezing concerns.
• Glycol is strongly recommended for hot water coils. It is the only reliable protection in the event of a power failure. Glycol's impact on coil and pump performance must be considered.
• An optional, non-averaging coil freezestat is offered on the downstream face of the heating coil. The outdoor dampers are shut, the fan is shut off, and the heating valve is fully opened, if freezing temperatures are experienced. The freezestat must be set somewhat above freezing temperatures to improve protection and may experience nuisance trips. It can not protect the coils during a power outage.
• Freeze protection strategies must not cause the cabinet temperature to exceed 150° F or motors and electrical equipment may be damaged.
The field installed supply and bleed off water lines can enter the unit through the floor, inside the curb perimeter. This may provide sufficient protection depending on the temperature inside the curb. Use freeze protection if there is any concern the temperature inside the curb may fall below freezing. If no curb is provided, or field water piping enters the side of the unit, then additional measures are required such as heat tape and proper pipe insulation.
• Hot water and steam coil piping can enter the floor of the unit in the heat section and requires similar consideration.
Condenser Water Connections
Supply and return condenser water piping, plus field connections for chemical water treatment, are shown in Figure 16 on page 22. Supply water can enter the floor of the service vestibule. Space is allowed in the vestibule for chemical tanks. Condenser bleed off (or return) connections allow easy drainage to a sanitary sewer through the floor of the vestibule.
The spray operation washes particles out of the condenser air and condenser heat rejection evaporates water. This process leaves behind minerals and particles that were contained in the water. Water bleed off and water treatment are required to prevent the build up of scale, sludge and microorganisms on the tube bundles and in the sump. These must be installed prior to unit start-up. See “Optional Water Treatment” on page 12.
22 Cat 219
Figure 16: Condenser Water Piping and Connections
Water Consumption
The theoretical water consumption required for proper heat rejection is 1.8 gallons per cooling ton hour. A nominal 100-ton unit, running at 50% capacity or 50 tons, evaporates 90 gallons of water per hour while rejecting condenser heat.
• Additional water must be added to the sump and bled off to the sanitary sewer to remove particles and minerals that accumulate in the water during operation. The required amount of bleed off varies with the water quality and is generally 0.6 to 0.9 gallons per ton hour or 33-50% of the theoretical evaporation water. Bleed off can be controlled in two ways.
• The RPE/RDE is provided with a manual shut off valve that can be used to adjust for a constant flow rate of bleed off water. This standard bleed off system can easily bleed off too much or too little water.
• Controlling bleed off with a solenoid valve, based on water conductivity or some other measure of particle concentration should be used. It is included in the RPE/RDE water treatment option.
• The RPE sump also has a float control that automatically opens the supply water solenoid and replaces water lost in evaporation and bleed off.
Water utility costs are usually based on the combination of water usage and sewer discharge. Only the bleed off portion of the water used by an evaporative condenser drains to the sewer (about 25-33% of total water used). Therefore, the sewer component of the cost of water may be reduced significantly if approved water meters are installed in the intake and bleed lines. The difference in meter rates reflects evaporation (water that will not go to the sewer) and this can be applied as a credit to the total water bill. Consult your local water utility for details.
Water Treatment
All evaporative condensers require proper water treatment. See “Optional Water Treatment” on page 12.
The purpose of the water treatment system is to:
• Control organic contamination.
• Reduce condenser and sump scaling, fouling and corrosion.
• Reduce the required cleaning frequency.
Proper water treatment involves 2 mandatory components (chemical treatment and bleed off) and may also require a solid separator system depending on water quality.
SprayPump
Optional FreezeProtection DrainValve
Manual DrainValve
OptionalWater TreatmentController
Supply toSump
Field Bleedoffor DrainConnection
From OptionalSeparator
To SpraySystem
To SpraySystem
Field SupplyWater Connection
ManualShut offValves
To OptionalSeparator andChemical Tanks
Hose Biband ManualShut offValve
RecommendedWater PipingEntranceThrough theCurb
AutomaticSupply Water Valve(Float Controlled)
RemovableSump Screen
FromSump
Sump Drain LeftOpen for Shipment
Cat 219 23
Selection InstructionsBuilding design and unit selection must allow for code compliance and installation limitations. The McQuay Rooftop unit offers excellent flexibility to meet diverse application requirements.
This catalog includes summary performance tables at several operating conditions. Performance at other conditions can be estimated by interpolation but accuracy may suffer. Extrapolation often results in unreliable or damaging operating conditions and should not be used without factory guidance that is available through your local sales representative. Contact your McQuay Representative for custom selections at specific design conditions.
Selection Example
Proper selection is illustrated based on the
following design criteria:
• 38,000 supply CFM at 2.00" ESP
• 36,000 return CFM at 0.75" ESP
• Sea level location using 60 Hertz power
• 95/ 75° F cooling ambient temperature
• 80/ 67° F cooling mixed air temperature [MAT]
Total cooling loads requirements:
• 115 total tons
• 87 sensible tons
Total sensible loads allow for:
• 50 HP SAF motor
• 25 HP RAF motor
Gas furnace requirements:
• 1520 MBH of design heating
• 9" gas pressure available at the unit
• Furnace to only be used at design CFM for morning warm up and night heat
• An RPE unit must be used since a furnace, or electric heat, or final filters are required.
Unit includes:
• Economizer plus return fan
• 65% filters plus pre-filters
Cooling Selection
Gross and Net Cooling
The tables within the section “Cooling Capacity Data” on page 26 provide gross cooling or DX coil capacity based on DX coil entering air temperature (EAT).
Net unit cooling capacity = [Gross cooling capacity] - [fan/ motor heat]
Fan/ motor heat is critical. Refer to “Indoor Fan and Motor Heat, Blow Through versus Draw Through Cooling” on page 17.
Fan/ motor heat = 2800 BTUH per BHP
Fan/ motor temperature rise (TR) = BTUH / (1.08 x CFM)
Mixed air vs. entering air temperature [MAT vs. EAT]
Draw through coil EAT = MAT
Blow through coil EAT = MAT + TR
Blow through EDB = mixed air EDB + TR
Use a psychometric chart to find blow through EWB.
Selection From Capacity Tables
Blow through vs. draw through. Refer to “Indoor Fan and Motor Heat, Blow Through versus Draw Through Cooling” on page 17.
An RPE is required due to the gas heat requirement. Therefore a draw through RPE will be considered first.
The RPE unit is available with both a low and high airflow DX coil. Refer to Table 7 on page 25.
First select a high and low airflow coil with sufficient capacity.
The RPE 110 with high airflow coil has sufficient capacity.
No low airflow coil has sufficient capacity.
Check coil velocity on all possible selections.
High airflow face area = 76.0 square feet face velocity = 526 feet per minute.
Low airflow face area = 60.8 square feet face velocity = 658 feet per minute
The low airflow velocity is too much per “Unit Operating Range (CFM and Temperature)” on page 16.
The RPE 110 [with high airflow coil] is sufficient per Table 15 on page 29.
RPE 110 provides 117.6 total tons.
RPE 110 provides 90.8 tons of sensible capacity.
RPE 110 power consumption.
90.0 compressor kW (see Table 15 on page 29).
4.0 condenser fan and pump kW (see Table 20 on page 32).
RPE 110 fan and motor heat must still be verified to be less than 50 = 25 BHP [per “fan selection”] to be sure that net cooling capacity is sufficient.
Heat SelectionSee Catalog 214 or 217 for hot water, steam and electric heat selection instructions.
Furnace SelectionSee Table 23 and Table 24 on page 34 and Table 25 on page 35.
Table 23 and Table 24 indicate all of the furnace output capacities available.
Output capacity is the true measure of furnace capacity
24 Cat 219
Output capacity = Input capacity x furnace efficiency
Furnace efficiency = 80% for McQuay furnaces [similar to most direct fired furnaces]
Net unit heating capacity =
Furnace heating capacity + fan / motor heat =
Furnace heating capacity + (50 + 25) X 2800 =
Furnace heating capacity + 210,000 BTUH
Net heating capacity must satisfy the heating load of 1520 MBH. A 1400 MBH furnace is the correct choice.
1,400,000 BTUH + 210,000 BTUH exceeds the 1,520 MBH requirement.
Airflow (cfm)Column Number (See Table 23 on page 34)
2 3 4 5 6 7 8 9 10
4000 0.05 - - - - - - - -
6000 0.1 - - - - - - - -
8000 0.17 0.14 0.08 0.07 - - - - -
10000 0.27 0.22 0.12 0.11 0.09 0.08 - - -
12000 0.39 0.32 0.17 0.16 0.13 0.12 0.09 0.08 -
14000 0.54 0.44 0.24 0.21 0.18 0.16 0.12 0.1 0.1
16000 0.7 0.57 0.31 0.28 0.24 0.2 0.15 0.13 0.12
18000 0.89 0.72 0.39 0.35 0.3 0.26 0.19 0.17 0.16
20000 1.09 0.89 0.48 0.43 0.37 0.32 0.24 0.21 0.2
22000 - 1.08 0.58 0.52 0.44 0.39 0.29 0.25 0.24
24000 - - 0.69 0.62 0.53 0.46 0.34 0.3 0.28
26000 - - 0.81 0.73 0.62 0.54 0.4 0.35 0.33
28000 - - 0.94 0.85 0.72 0.63 0.47 0.41 0.38
30000 - - 1.08 0.97 0.83 0.72 0.54 0.47 0.44
32000 - - 1.23 1.11 0.94 0.82 0.61 0.53 0.5
34000 - - - 1.25 1.06 0.92 0.69 0.6 0.56
36000 - - - - 1.19 1.04 0.77 0.68 0.63
38000 - - - - - 1.15 0.86 0.75 0.7
40000 - - - - - - 0.95 0.84 0.78
42000 - - - - - - 1.05 0.92 0.86
44000 - - - - - - 1.15 1.01 0.94
46000 - - - - - - - 1.11 1.03
48000 - - - - - - - 1.2 1.12
50000 - - - - - - - - 1.22
36 Cat 219
Gas Piping Schematic
Figure 22: Gas Piping Schematic
Table 26: Gravity Relief Damper Air Pressure Drop - 0-100% Economizer
Note: If all exhaust must occur through the economizer gravity relief damper, and no return or exhaust fan is provided, then the building may be pressurized by the sum of the return duct pressure drop plus the gravity relief pressure.
Item Description
ETL/UL ETL-C IRI/FIA FM
200-400
Mbh
500-2000
Mbh
200-400
Mbh
500-2000
Mbh
400-1000
Mbh
1100-2000
Mbh
500-2000
Mbh
1-8
(1) Forced Draft Blower (2) Combination Air
Switch (3) Pilot Cock (4) Pilot Pressure
Regulator (5) Pilot Gas Valve (6) Pilot
Orifice (7) Main Gas Orifice (8) Manifold
Pressure Tap
S S S S S S S
9 High Pressure Switch - - - - - S -
10 Test Cock B B B B L L B
11 Leak Test Tap Cock - - - - S S -
12 Shutoff Valve C S C - - H -
13 Vent To Atmosphere Valve, N/O - - - - - S -
14 Shutoff Valve C S C H HP H HP
15 Low Pressure Switch - - - - - S -
16 Main Pressure Regulator C S C S S S S
17 Main Gas Shutoff Cock B B B L L L B
18-22
(18) High Pressure Regulator (19)
Lubricated Shutoff Cock (20) Combustion
Air Butterfly Valve (21) Main Gas Butterfly
Valve (22) Modulating Operator
O O O O O O O
Exhaust CFM 20000 25000 30000 35000 40000
Size 076C-150C .25 .35 .48 .66 .85
Cat 219 37
Component Pressure Drops
Table 27: Component Pressure Drops
Table 28: Cooling Coil Air Pressure Drop
Note: DX coil pressure drops are based on wet coils.
Note: Pressure drop of cooling coils not shown can be found in the McQuay selection program output.
a. Pressure drop through hood and damper is based on 30% of listed airflow.b. Pressure drop through the economizer assumes that the majority of air will be passing through the return air dampers. If large quantities of outside air are required, pressure
drops will increase causing airflow to decrease.c. A diffuser is provided on units with blow-through cooling coils, final filters or hydronic heating.
Figure 47: Units with Side Discharge - Remove Access Door and Connect Ductwork as Shown
Table 29: Typical Cross Section - Internal Cabinet Clearance - Air in the Face
Unit Floor Base Rail
Condensing Section Walk-in Service Compartment
4272
42
3.6
3.5
1.81.8
6.0
1.82.2
5.2
8.5
3.0
85
CabinetHeight
Airflow85
AirflowRPE Units -
Discharge is out the side of the Discharge Plenum
RDE Units -
Discharge is out the side of the Supply Fan section.
RDE/RPE C D E F
076C-150C 91.7 96 91.8 95
C = Ceiling-to-floor (with liners)D = Door-to-door (with liners)E = Upright-to-upright, located between sectionsF = Base-to-base
Cat 219 51
Electrical Data
Table 30: Condensing Unit
Note: 1. Data given is for individual compressors and condenser fan motors. 2. AL = Across-the-Line start; PW = Part Winding start 3. Locked Rotor Amps for part winding start are for the first winding for 1 second. 4. 115 volt receptacle or marine light options require separate power service.
Unit
Size
Compressor Data Condenser Fan Motors *
HP Qty VoltageRLA Each LRA Each
HP QtyFLA
Each
LRA
EachAL PW AL PW
076C 30 2
208 106 106 470 292 1.5 4 5.0 26.0
230 106 106 470 292 1.5 4 5.0 26.0
460 53 53 235 141 1.5 4 2.5 13.0
575 36 36 217 130 1.5 4 2.0 11.5
089C 35 2
208 112 112 565 340 1.5 4 5.0 26.0
230 112 112 565 340 1.5 4 5.0 26.0
460 56 61 283 156 1.5 4 2.5 13.0
575 45 45 230 138 1.5 4 2.0 11.5
100C 40 2
208 152 152 660 440 1.5 4 5.0 26.0
230 140 140 594 340 1.5 4 5.0 26.0
460 71 71 297 170 1.5 4 2.5 13.0
575 54 54 235 135 1.5 4 2.0 11.5
110C 25 4
208 77 77 428 250 1.5 6 5.0 26.0
230 77 77 428 250 1.5 6 5.0 26.0
460 39 42 214 117 1.5 6 2.5 13.0
575 31 31 172 103 1.5 6 2.0 11.5
130C 30 4
208 106 106 470 292 1.5 6 5.0 26.0
230 106 106 470 292 1.5 6 5.0 26.0
460 53 53 235 141 1.5 6 2.5 13.0
575 36 36 217 130 1.5 6 2.0 11.5
140C
Comp. 1 & 330 2
208 106 106 470 292 1.5 3 5.0 26.0
230 106 106 470 292 1.5 3 5.0 26.0
460 53 53 235 141 1.5 3 2.5 13.0
575 36 36 217 130 1.5 3 2.0 11.5
140C
Comp. 2 & 435 2
208 112 112 565 340 1.5 3 5.0 26.0
230 112 112 565 340 1.5 3 5.0 26.0
460 56 61 283 156 1.5 3 2.5 13.0
575 45 45 230 138 1.5 3 2.0 11.5
150C 35 4
208 112 112 565 340 1.5 6 5.0 26.0
230 112 112 565 340 1.5 6 5.0 26.0
460 56 61 283 156 1.5 6 2.5 13.0
575 45 45 230 138 1.5 6 2.0 11.5
52 Cat 219
Table 31: Supply, Exhaust and Return Fan Motors
Note: 1. For 380/50/3 applications, 460/60/3 motors are used. Derate nameplate by 0.85 to obtain actual horsepower.
Table 32: 1.5 HP Spray Pump for All Sizes
Table 33: Optional Sump Heater
Fan Motor 208/60/3 230/60/3 460/60/3 (1) 575/60/3
HP Efficiency FLA LRA FLA LRA FLA LRA FLA LRA
5
High ODP 14.8 106 14 94 7 47 5.3 38
High TEFC 14.6 126 13.4 102.4 6.7 51.2 5.4 39
Premium ODP 15.7 110 13.6 96 6.8 48 5.2 38.4
7.5
High ODP 22.3 137 21.6 147.4 10.8 74.2 8.2 49
High TEFC 21.4 198 20.4 145.2 10.2 72.6 8.2 58
Premium ODP 22.3 185 20 122 10 80 7.4 52
10
High ODP 29.7 290 28 180 14 94 11 72
High TEFC 28.5 228 28.4 200 14.2 100 11.4 80
Premium ODP 29 247 25.8 192 12.9 106 10.3 76.6
15
High ODP 44.4 326 40.6 301 20.3 150.5 16.2 120
High TEFC 40.3 248 38.8 272 19.4 136 15.5 109
Premium ODP 43.4 269 37.8 233.6 18.9 117 14.1 94
20
High ODP 57 342 50 350 25 175 20 135
High TEFC 54 335 48 320 24 160 19.1 123
Premium ODP 57 377 49 322 24.5 160 18.9 130
25
High ODP 69.8 427 62 382 31 191 24.3 151
High TEFC 66 413 60 380 30 190 24.2 152
Premium ODP 70.5 384 61 380 30.5 190 24.2 125
30
High ODP 86.5 461 75 460 37.5 230 30 177
High TEFC 82 496 72 460 36.0 230 28.6 184
Premium ODP 83.3 506 72.4 448 36.2 224 29.8 178
40
High ODP 117 660 102 630 51 315 40 251
High TEFC 115 661 95 544 47.5 272 38 214
Premium ODP 110 660 96 630 48 315 38 245
50
High ODP 138 826 124 770 62 385 49.2 303
High TEFC 142 742 118 744 59 372 48 266
Premium ODP 137 955 120 752 60 376 47.5 332
60
High ODP 154 991 144 872 72 442 57.4 355
High TEFC 159 1035 140 1022 70 511 56 409
Premium ODP 159 1125 140 912 70 456 56 345
75
High ODP 189 1240 176 1108 88 553 71 505
High TEFC 196 1242 172 1132 86 566 68 447
Premium ODP 195 1240 170 1044 85 553 65.5 444
Voltage 208 230 460 575
FLA 4.8 4.8 2.4 2.0
Voltage 208 230 460 575
FLA 19.2 16.7 8.7 6.9
Cat 219 53
Supply Power Wiring
Table 34: Electric Heat
Table 35: Recommended Power Wiring
1. Units require three-phase power supply.
2. Allowable voltage tolerances:a. 60 Hertz
Nameplate 208V: Min. 187V, Max. 229VNameplate 230V: Min. 207V, Max. 253VNameplate 460V: Min. 414V, Max. 506VNameplate 575V: Min. 518V, Max. 633V
b. 50 HertzNameplate 380V: Min. 360V, Max. 418V
3. Minimum Circuit Ampacity (MCA) Calculation:
Note: If a unit is provided with multiple power connec-tions, each must be considered alone in selecting power wiring components.
MCA Calculation
The MCA is calculated based on the following formulas:
1. Units with cooling and all heating except electric heat MCA = 1.25 x largest load + sum of all other loads
2. On units with electric heat, the MCA is computed both in the cooling mode and the heating mode and the greater of the two values is used.
a. Heating Mode
Electric heat less than or equal to 50kW
MCA = 1.25 (sum of all loads including electric heat)
Electric heat greater than or equal to 50kW
MCA = 1.25 (sum of all SAF, RAF or EAF loads) plus electric heat load
Note: the compressor and condenser are not included in this calculation.
b. Cooling Mode
MCA = 1.25 x largest load + sum of all the other loads
Note: Control circuit ampacity does not need to be considered in the calculation for wire sizing ampacity. If the unit is provided with one or more fan section lights, they are powered from the separate 15 amp (minimum), 120V supply required by the NEC for the unit convenience outlet.
3. Size wires in accordance with Table 310-16 or 310-19 of the National Electrical Code.
4. Wires should be sized for a maximum of 3% voltage drop.
2’’, 1.5 Lb. density insulation with Solid Liners:30 30 30 30 30 30 30
Weight Per Foot Of Unit Length
Sound Attenuators
Sound Attenuator with Gas or Electric Heat 1708
Sound Attenuator without Gas or Electric Heat 1321
Components Unit Size
076C 089C 100C 110C 130C 140C 150C
a.Basic unt consists of return air plenum, angular filter section, supply air fan section without fan or motor, cooling section without coil, condensing unit and service vestibule.b.Final filter option includes liners in the filter section and discharge plenum.c.Does not include weight of 4 ft. blank section.d. Excluding condensing unit section and vestibule.
56 Cat 219
Fan Motor Weights
Roof Curb WeightsCalculate the weight of the unit curb using the following equation and adding additional weights accordingly.
Note: Curb length does not include condenser length.
Additional Weights:
1. Cross supports:
• For curb length greater than 144 in, add 30 lb.• For curb length greater than 288 in, add 60 lb.• For curb length greater than 432 in, add 90 lb.• For curb length greater than 576 in, add 120 lb.
2. For condenser section support rail, add 139 lb. for sizes 076C-100C and 278 lb. for sizes 110C to 150C.
Example: RPE100C
Note: Roof curb weight should be considered for structural purposes
Motor HPWeight (lbs.)
Open Drip-Proof Totally Enclosed
5 82 85
7.5 124 140
10 144 170
15 185 235
20 214 300
25 266 330
30 310 390
40 404 510
50 452 570
60 620 850
75 680 910
Unit Size Weight Formula
All Base curb wt. (lb.) = 0.74 [200 + 2 x curb length (in)]
Component Lbs.
Basic unit 15,322
Economizer 1,266
30% efficiency filters 6
Burglar bars, supply 69
Burglar bars, return 114
36’’ airfoil supply fan 1,719
44’’ airfoil return fan 971
DX coil - 5-row 12 FPI, high airflow aluminum fins 1,528
Gas heat - 1000 mbh 650
SAF motor - 40 HP 404
RAF motor - 15 HP 185
Liners 1080
23,314
Liner Calculations ft
Section - Economizer 8
Filter 2
Supply fan 8
Heat 4
DX coil 4
Discharge plenum 4
Service Compartment 6
x 30 lbs. per ft. 36
1080
Cat 219 57
Engineering Guide Specification
RoofPak™ Singlezone Heating and Cooling Unit(s) model [RPE] [RDE]
General
A. The complete unit shall be [ETL/MEA] [ETL-Canada] listed. The burner and gas train for the unit furnace shall be [ETL/UL] [ETL Canada] [IRI/FIA] [FM] approved.
B. Each unit shall be specifically designed for outdoor rooftop application and include a weatherproof cabinet. Units shall be of a modular design with factory installed access sections available to provide maximum design flexibility. Each unit shall be [completely factory assembled and shipped in one piece] [split between the supply fan section and the heat section]. [RPE and RDE packaged units shall be shipped fully charged with Refrigerant [22] [407C]]. [All units split for shipment include a nitrogen holding charge only.]
C. The unit shall undergo a complete factory run test prior to shipment and factory test sheets shall be available upon request. The factory test shall include final balancing of the supply [and return] fan assemblies, a refrigeration circuit run test, a unit control system operations checkout, [test and adjustment of the gas furnace], a unit refrigerant leak test and a final unit inspection.
D. All units shall have decals and tags to indicate caution areas and aid unit service. Unit nameplates shall be fixed to the main control panel door. Electrical wiring diagrams shall be attached to the control panels. Installation, operating and maintenance bulletins and start-up forms shall be supplied with each unit.
E. Performance: All scheduled capacities and face areas are the minimum accepted value. All scheduled amps, KW, and HP are maximum accepted values that allow scheduled capacity to be met.
Cabinet, Casing and Frame
A. Standard double-wall construction for all side wall access doors and floor areas shall be provided with heavy gauge solid galvanized steel inner liners to protect insulation during service and maintenance. Insulation shall be a minimum of 1" thick, 3/4 lb. density neoprene coated glass fiber. Unit cabinet shall be designed to operate at total static pressures up to 6.5 inches w.g. Insulation on ceiling and end panels shall be secured with adhesive and mechanical fasteners. [26 gauge solid galvanized steel liners shall be provided throughout, allowing no exposed insulation within the air stream. All cabinet insulation, except floor panels, shall be a nominal 2" thick, 1 ½ lb. density, R6.5, glass fiber. Floor panels to be a minimum 1" thick, 3 lb. density, R4.2, glass fiber.] [Perforated liners shall be used in the supply and return air plenums, to improve sound attenuation] [All floor
panels shall be double wall construction and include a nominal 2" thick, 1 ½ lb. density, R6.5 glass fiber insulation.]
B. Exterior surfaces shall be constructed of pre-painted galvanized steel for aesthetics and long term durability. Paint finish to include a base primer with a high quality, polyester resin topcoat of a neutral beige color. Finished surface to withstand a minimum 750-hour salt spray test in accordance with ASTM B117 standard for salt spray resistance.
C. Service doors shall be provided on both sides of each section in order to provide user access to all unit components. Service doors shall be constructed of heavy gauge galvanized steel with galvanized steel interior liners. All service doors shall be mounted on multiple, stainless steel hinges and shall be secured by a stainless steel latch system that is operated by a single handle. The latch system shall feature a staggered engagement for ease of operation and a safety catch shall protect the user from injury in case a positive pressure door is opened while the fan is operating. Removable panels, or doors secured by multiple, mechanical fasteners are not acceptable.
D. The unit base frame shall be constructed of 13-gauge pre-painted galvanized steel. The unit base shall overhang the roof curb for positive water runoff and shall have a formed recess that seats on the roof curb gasket to provide a positive, weather tight seal. Lifting brackets shall be provided on the unit base with lifting holes to accept cable or chain hooks.
Supply, Return and Exhaust Fans
A. All return and supply fan assemblies shall be statically and dynamically balanced at the factory, including a final trim balance, prior to shipment. All fan assemblies shall employ solid steel fan shafts. Heavy-duty pillow block type, self-aligning, grease lubricated ball bearings shall be used. Bearings shall be sized to provide an L-50 life at 200,000 hours. The entire fan assembly shall be isolated from the fan bulkhead and mounted on [rubber-in-shear isolators] [spring isolators] [spring isolators with seismic restraints]. [Fixed] [Adjustable] pitch V-belt drives with matching belts shall be provided. V-belt drives shall be selected at [the manufacturer's standard service factor] [1.5 times fan brake horsepower].
B. Return and supply fan motors shall be heavy-duty 1800 rpm [open drip-proof (ODP)] [totally enclosed TEFC] type with grease lubricated ball bearings. [Motors shall be high efficiency and meet applicable EPACT requirements.] [Motors shall be premium efficiency.] Motors shall be mounted on
58 Cat 219
an adjustable base that provides for proper alignment and belt tension adjustment.
C. DWDI Supply Air Fan (RPE)
1. Supply fan shall be a double width, double inlet (DWDI) airfoil centrifugal fan. All fans shall be mounted using shafts and hubs with mating key-ways.
2. All fans shall be Class II type and fabricated from heavy-gauge aluminum. Fan blades shall be continuously welded to the back plate and end rim.
D. SWSI Supply Air Fan (RDE)
1. Supply fan shall be single-width, single inlet (SWSI) airfoil centrifugal fan.
2. The fan wheel shall be Class II construction and fabricated from painted steel with fan blades continuously welded to the back plate and end rim. Fans shall be mounted using shafts and hubs with mating keyways.
E. Return Air Fans
1. A single width, single inlet (SWSI) airfoil centrif-ugal return air fan shall be provided. The fan wheel shall be Class II construction and fabri-cated from heavy-gauge aluminum with fan blades continuously welded to the back plate and end rim. The fan shall be mounted using shafts and hubs with mating keyways.
2. Exhaust or relief fans are not acceptable.
F. Exhaust Fans
1. Belt drive propeller exhaust fans shall be pro-vided. Propeller fans shall be constructed with fabricated steel, and shall be securely attached to fan shafts. All fans shall be statically and dynamically balanced.
2. Motors shall be permanently lubricated, heavy-duty type, carefully matched to the fan load.
3. Ground and polished steel fan shafts shall be mounted in permanently lubricated, sealed ball bearing pillow blocks. Bearings shall be selected for a minimum (L10) life in excess of 100,000 hours at maximum cataloged operating speeds. Drives shall be sized for a minimum of 150 per-cent of driven horsepower. Pulleys shall be of the fully machined cast iron type, keyed and securely attached to wheel and motor shafts. Motor sheaves shall be adjustable for system balancing.
4. Drive frame and panel assemblies shall be galva-nized steel. Drive frames shall be formed chan-nels and panels shall be welded construction.
5. The axial exhaust fans shall bear the AMCA Cer-tified Ratings Seal for both sound and air perfor-mance. Return fans are not acceptable.
G. The [supply air fan] [supply and return/exhaust air fan] sections shall be provided with an expanded metal belt guard.
VAV, Variable Frequency Drive Control
A. An electronic variable frequency drive shall be provided for the supply air fan [and another for the return or exhaust fan]. [Each drive shall be factory installed in a designated access section upstream of the cooling coil, in a manner that the drive[s] are directly cooled by the mixed air stream]. [Each drive shall be mounted in the fan section]. Drives shall meet UL Standard 95-5V and the variable frequency drive manufacturer shall have specifically approved them for plenum duty application. The completed unit assembly shall be listed by a recognized safety agency, such as ETL. Drives are to be accessible through a hinged door assembly complete with a single handle latch mechanism. Mounting arrangements shall not expose drives to high temperature, unfiltered ambient air.
B. The unit manufacturer shall install all power and control wiring. [A manual bypass contactor arrangement shall be provided. The bypass arrangement will allow fan operation at full design CFM, even if the drive has been removed for service]. [Line reactors shall be factory installed for each drive].
C. The supply air fan drive output shall be controlled by the factory installed main unit control system and drive status and operating speed shall be monitored and displayed at the main unit control panel. [The supply and return/exhaust fan drive outputs shall be independently controlled in order to provide the control needed to maintain building pressure control. Supply and return/exhaust air fan drives that are slaved off of a common control output are not acceptable.]
D. All drives shall be factory run tested prior to unit shipment.
Electrical
A. Unit wiring shall comply with NEC requirements and with all applicable UL standards. All electrical components shall be UL recognized where applicable. All wiring and electrical components provided with unit shall be number and color-coded and labeled according to the electrical diagram provided for easy identification. The unit shall be provided with a factory wired weatherproof control panel. A terminal board shall be provided for field control wiring connections. Branch short circuit protection, 115-volt control circuit transformer and fuse, system switches, high temperature sensor, and a 115 volt receptacle with a separate electrical connection shall also be provided with unit. [A second 115v power supply is required to power the optional unit heater.] Each compressor and condenser fan motor shall be furnished with contactors and inherent thermal overload protection. Supply and return fan motors shall have contactors and current sensing overload protection. Knockouts shall be provided in the bottom of the main control panels for field wiring
Cat 219 59
entrance. All 115-600 volt internal and external wiring between control boxes and components shall be protected from damage by raceways or conduit.
B. [A single main terminal block shall be provided for connecting electrical power at the unit.] [A single non-fused main disconnect switch shall be provided for connecting electrical power at the unit. The switch shall be mounted internal to the control panel and operated by an externally mounted handle. External handle to be designed to prohibit opening of the control panel door without the use of a service tool.] [Dual non-fused disconnect switches shall be provided for connecting electrical power at the unit. One switch shall service the unit supply (and return) (and exhaust) fan(s) and the unit control panel. The second switch shall service the unit condensing section. Switches shall be mounted internal to the control panel and operated by an externally mounted handle. External handle to be designed to prohibit opening of the control panel door without the use of a service tool.]
C. [A factory installed and wired marine service light, with switch and receptacle, shall be provided in the supply air fan section. The separate, main unit service receptacle electrical circuit shall also power the light circuit.] [Factory installed and wired marine service lights, with switches and receptacles, shall be provided in the supply air and return/exhaust air fan sections. The separate, main unit service receptacle electrical circuit shall also power the light circuits.]
D. [Part winding start shall be provided for the unit compressors to reduce inrush current at start-up.]
E. [Power factor capacitors shall be factory mounted and wired to the unit (compressors) (supply and return air fan motors) (compressors and supply and return air fan motors). Power factor capacitors shall be selected to provide correction to a minimum of 0.90.]
F. [Phase failure and under voltage protection shall be provided to prevent damage from single phasing, phase reversal, and low voltage conditions.]
G. Ground fault protection shall be provided to protect against arcing ground faults.]
H. [Factory mounted smoke detectors shall be installed in the (supply air opening) (supply and return air openings). Smoke detectors to be ionization type, which responds to invisible products of combustion without requiring the sensing of heat, flame or visible smoke. Upon sensing smoke, the unit shall provide a control output for use by building management system such that the building management system can issue the required safety commands.]
I. Unit to have factory mounted ultraviolet germicidal irradiation (UVGI) lamps located on the leaving air side of the cooling coil. UVGI lamps to constantly irradiate the cooling coil and drain pan surfaces
with light in the 254-nanometer wavelength of the light spectrum (UV-C) for germicidal effect. View port(s) with glass rated to block ultraviolet light shall be included to allow for visual inspection during operation. Automatic disconnect switches shall kill power to the lamps whenever an associated door is opened.
Lamp and fixture to consist of housing, power source, lamp sockets and lamp. Housing shall be type 304 stainless steel and all components are to be constructed to withstand saturated air conditions typical of HVAC environments. Lamps are to be designed to facilitate simple fixture to fixture plug-in for AC power. Power source to provide maximum radiance and reliability at UL/C-UL Listed temperatures of 55-135°F. Power source to include RF and EMI suppression. Lamps to be high-output hot cathode, T8 diameter, medium I-pin type that produces UVGI of 254nm. Lamps to produce the specified output at 500 fpm and air temperatures of 55-135°F.
Lamps and fixtures shall be UL/C-UL listed and the complete equipment/UVGI light package shall include Intertek Services Inc. (ETL) safety agency certification.
Heating and Cooling Sections
Cooling
A. [The cooling coil section shall be installed in a blow through configuration, downstream of the supply air fan. A factory-tested diffuser shall be used in order to provide air distribution across the cooling coil. A blow through coil is specified to minimize the impact of fan motor heat. Scheduled supply air temperature (SAT) is design cooling SAT at the unit discharge after all fan motor heat is considered and equals leaving air temperature (LAT) from a blow through DX coil. A draw through alternative must meet scheduled SAT after all fan motor heat is added to the draw through DX LAT. A draw through submittal must clearly provide DX coil LAT, fan motor heat temperature rise, and unit SAT.] [The cooling coil section shall be installed in a draw through configuration, upstream of the supply air fan.] The coil section shall be complete with factory piped cooling coil and sloped drain pan. Hinged access doors on both sides of the section shall provide convenient access to the cooling coil and drain pan for inspection and cleaning.
B. Cooling coil performance schedule is based on mixed air and coil leaving air temperatures, not including fan motor heat. Manufacturer shall add motor heat [to the mixed air to calculate DX coil entering air temperature on blow through designs] [to the DX coil LAT to calculate unit SAT on draw through models.] Scheduled total and sensible capacities are gross capacities, are minimum accepted values, and do not include fan motor heat
C. Direct expansion (DX) cooling coils shall be fabricated of seamless 1/2” diameter high efficiency copper tubing that is mechanically
60 Cat 219
expanded into high efficiency [aluminum] [copper] plate fins. Coils shall be a multi-row, staggered tube design with a minimum of [3] [4] [5] rows and a maximum of [8] [10] [12] fins per inch. All multiple compressor units shall have two independent refrigerant circuits and shall use an interlaced coil circuiting that keeps the full coil face active at all load conditions.
D. All coils shall be factory leak tested with high pressure air under water.
E. [A painted galvanized steel, positively sloped drain pan shall be provided with the cooling coil.] [A stainless steel, positively sloped drain pan shall be provided with the cooling coil.] The drain pan shall extend beyond the leaving side of the coil and underneath the cooling coil connections. The drain pan shall have a minimum slope of 1/8 in. per foot to provide positive draining. The drain pan shall be connected to a threaded drain connection extending through the unit base. Units with stacked cooling coils shall be provided with a secondary drain pan piped to the primary drain pan.
Hot Water Heating
F. A [1] [2] row hot water heating coil shall be factory installed in the unit heat section. Coils shall be fabricated of seamless 5/8 in. diameter copper tubing that is mechanically expanded into high efficiency HI-Fá rippled and corrugated aluminum plate fins. All coil vents and drains shall be factory installed. [The hot water heat section shall be installed downstream (RPE) of the supply air fan. A factory-tested diffuser shall be used in order to provide air distribution across the coil.] [The hot water heat section shall be installed upstream (RDE) of the supply air fan.] Hinged access doors on both sides of the unit shall provide convenient access to the coil and valve for inspection and cleaning.
G. [A factory installed three-way modulating control valve and spring return valve actuator shall provide control of the hot water coil. The valve actuator shall be controlled by the factory installed main unit control system]
H. [Ethylene glycol] [propylene glycol] shall be added to the hot water circuit to protect against coil freeze-up.]
I. [A factory installed, non-averaging type freezestat shall be factory installed to provide additional protection against coil freeze-up.]
J. Coils shall be factory leak tested with high pressure air under water.
Steam Heating
K. A [1] [2] row, [6] [12] fin per inch steam heating coil shall be factory installed in the unit heat section. Coils shall be fabricated of seamless 5/8 in. diameter copper tubing that is mechanically expanded into high efficiency HI-F rippled and corrugated aluminum plate fins. Steam coils shall be of the jet distributing type. [The steam heat
section shall be installed downstream (RPE) of the supply air fan. A factory-tested diffuser shall be used in order to provide air distribution across the coil.] [The steam heat section shall be installed upstream (RDE) of the supply air fan.] Hinged access doors shall provide convenient access to the coil and valve for inspection and cleaning.
L. [A factory installed two-way modulating control valve and spring return valve actuator shall provide control of the steam coil. The valve actuator shall be controlled by the factory installed main unit control system]
M. [A factory installed, non-averaging type freezestat shall be factory installed to provide some protection against coil freeze-up.]
N. Coils shall be factory leak tested with high pressure air under water.
Gas Heating (RPE Only)
O. A natural gas fired furnace shall be installed in the unit heat section. The heat exchanger shall include a type 321 stainless steel cylindrical primary combustion chamber, a type 321 stainless steel header, type 321 stainless steel secondary tubes and type 321 stainless steel turbulators. Carbon and aluminized steel heat exchanger surfaces are not acceptable. The heat exchanger shall have a condensate drain piped to the unit exterior. Clean out of the primary heat exchanger and secondary tubes shall be accomplished without removing casing panels or passing soot through the supply air passages. The furnace section shall be positioned downstream of the supply air fan.
P. [The furnace will be supplied with a modulating forced draft burner. The burner shall be controlled for low fire start. The burner shall be capable of continuous modulation between 33% and100% of rated capacity and shall operate efficiently at all firing rates.] [The furnace shall be supplied with a McQuay SuperMod™ forced draft burner capable of continuous modulation between 5% and 100% of rated capacity, without steps.] The burner shall operate efficiently at all firing rates. The burner shall have proven open damper low-high-low pre-purge cycle, and proven low fire start. The combustion air control damper shall be in the closed position during the off cycle to reduce losses. The burner shall be rated for operation and full modulation capability at inlet gas pressures down to [5.0 in. W.C. (models 1100, 1400, 1500)] [5.5 in. W.C. (model 500)] [6.0 in. W.C. (model 2000)] [6.5 in. W.C. (models 790, 800, 1000)] [7.0 in. W.C. (models 640, 650)].[The shutoff cock and test cock shall be fully ported ball valves.]
Q. The burner shall be specifically designed to burn natural gas and shall include a microprocessor based flame safeguard control, combustion air proving switch, pre-purge timer and spark ignition. The gas train shall include redundant gas valves, [maximum 0.5psi pressure regulator] [2-3psi high pressure regulator] [5-10psi high pressure
Cat 219 61
regulator], shutoff cock, pilot gas valve, pilot pressure regulator, and pilot cock.
R. [The gas burner shall be controlled by the factory installed main unit control system]
S. The burner shall be fired, tested and adjusted at the factory. Final adjustments shall be made in the field at initial start-up by a qualified service technician to verify that installation and operation of the burner is according to specifications.
Electric Heating (RPE Only)
T. Staged electric heating coils shall be factory installed in the unit heat section. Heating coils shall be constructed of a low watt density, high nickel-chromium alloy resistance wire, mechanically stacked and heli-arc welded to corrosion resistant terminals. A corrosion resistant heavy gauge rack shall support the elements. Safety controls shall include automatic reset high limit control for each heater element with manual reset backup line break protection in each heater element branch circuit (Note: Manual reset not provided when ETL-Canada label is provided). Heating element branch circuits shall be individually fused to maximum of 48 Amps per NEC requirements. The electric heat section shall be positioned downstream of the supply air fan.
U. [The electric heat elements shall be controlled by the factory installed main unit control system]
Cooling Only
V. A blank heat section shall be provided between the supply fan and blow-thru cooling coil section.
Filters
Draw Thru Filters
A. Unit shall be provided with a draw-through filter section. The filter section shall be supplied complete with the filter rack as an integral part of the unit. The draw-through filter section shall be provided with [panel] [cartridge] filters.
B. [2" thick AmericanAirFilter 30% efficient pleated panel filters shall be provided. Filters shall be frame mounted and shall slide into galvanized steel racks contained within the unit. Filters shall be installed in an angular arrangement to maximize filter area and minimize filter face velocity. Filters shall be accessible from both sides of the filter section.]
C. [12" deep [60-65%] [90-95%] efficient, UL Std. 900, Class 1, AmericanAirFilter cartridge filters shall be provided. 2" panel, 30% efficient pre-filters shall be included. Cartridge filters shall consist of filter media permanently attached to a metal frame and shall slide into a gasketed, extruded aluminum rack contained within the unit. The filter rack shall have secondary gasketed, hinged end panels to insure proper sealing. Filters shall be accessible from both sides of the filter section.]
D. [[30% efficient pleated] [60-65% efficient cartridge] [90-95% efficient cartridge] filters shall be provided with INTERSEPT™ antimicrobial treatment.]
Final Filters (RPE Only)
E. Final Filters - Unit shall be provided with a final filter section. The final filter section shall be supplied complete with the filter rack as an integral part of the unit. The final filter section shall be provided with cartridge filters.
F. 12" deep 90-95% efficient, UL Std. 900, Class 1, AmericanAirFilter cartridge filters shall be provided. For units with gas or electric heat, AmericanAirFilter High Temperature cartridge filters rated for 500° F shall be used. Cartridge filters shall consist of filter media permanently attached to a metal frame and shall slide into a gasketed, extruded aluminum rack contained within the unit. The filter rack shall have secondary gasketed, hinged end panels to insure proper sealing. Filters shall be accessible from both sides of the filter section.
G. [Filters shall be provided with INTERSEPT™ antimicrobial treatment.]
Outdoor / Return Air Section
Return Air Plenum
A. Unit shall be provided with a return air plenum for handling 100% re-circulated air. The 100% return air plenum shall allow return air to enter from the [bottom] [back] of the unit.
Return Air Plenum with 0 to 30% Outdoor Air Hood
B. A return air plenum shall be provided with a 0 to 30% outdoor air hood. The hood shall allow outdoor air to enter at the back of the return air plenum. The outdoor air hood shall be factory installed and constructed from galvanized steel finished with the same durable paint finish as the main unit. The hood shall include a bird screen to prevent infiltration of foreign materials and a rain lip to drain water away from the entering air stream. The return air plenum shall allow return air to enter from the [bottom] [back] of the unit.
0 - 100% Outdoor Air Economizer
C. Unit shall be provided with an outdoor air economizer section. The 0 to 100% outside air economizer section shall include outdoor, return, and exhaust air dampers. Outdoor air shall enter from both sides of the economizer section through horizontal, louvered intake panels complete with rain lip and bird screen. The floor of the outdoor air intakes shall provide for water drainage. The economizer section shall allow return air to enter from the [bottom] [back] of the unit. The outside and return air dampers shall be sized to handle 100% of the supply air volume. The dampers shall be opposed sets of parallel blades, arranged vertically to converge the return air and outdoor air streams in multiple, circular mixing patterns.
62 Cat 219
D. McQuay UltraSeal™ low leak dampers shall be provided on outdoor and return dampers. Damper blades shall be fully gasketed and side sealed and arranged horizontally in the hood. Damper leakage shall be less than 0.5% at 1.5 inches static pressure differential. Leakage rate to be tested in accordance with AMCA Standard 500. Damper blades shall be operated from multiple sets of linkages mounted on the leaving face of the dampers.
E. A barometric exhaust damper shall be provided to exhaust air out of the back of the unit. [An electric actuator shall provide positive closure of the exhaust damper.] Exhaust louvers and a bird screen shall be provided to prevent infiltration of rain and foreign materials. Exhaust damper blades shall be lined with urethane gasketing on contact edges.
F. [Control of the outdoor or return dampers shall be by a factory installed actuator. Damper actuator shall be of the modulating, spring return type. If outdoor air is suitable for “free” cooling, the outdoor air dampers shall modulate in response to the unit's temperature control system.] [An adjustable enthalpy control shall be provided to sense the dry-bulb temperature and relative humidity of the outdoor air stream to determine if outdoor air is suitable for “free” cooling.] [A comparative enthalpy control shall be provided to sense and compare enthalpy in both the outdoor and return air streams to determine if outdoor air is suitable for “free” cooling.]
DesignFlow™ Minimum Outdoor Air Measurement
and Control
G. The 0 - 100% outdoor air economizer system shall include the DesignFlow minimum outdoor air control systems that directly measures the total mass volume of air flowing through the outdoor air intakes. The unit's control panel shall automatically adjust the outdoor damper position to maintain minimum outdoor air cfm. The airflow station shall be capable of accurately measuring outdoor air volume within 5% to continuously satisfy the requirements of ASHRAE 62 - 1999. Third party verification of measurement accuracy shall be verified by a nationally recognized independent testing agency.
100% OA Hood
H. Unit shall be provided with a 100% outdoor air hood. The 100% outdoor air hood shall allow outdoor air to enter from the back of the unit, at the draw-through filter section. The outdoor air hood shall be factory installed and constructed from galvanized steel finished with the same durable paint finish as the main unit. The hood shall include a bird screen to prevent infiltration of foreign materials and a rain lip to drain water away from the entering air stream.
I. McQuay UltraSeal™ low leak dampers shall be provided. Damper blades shall be fully gasketed
and side sealed and arranged vertically in the hood. Damper leakage shall be less than 0.5% at 1.5 inches static pressure differential. Leakage rate to be tested in accordance with AMCA Standard 500. Damper blades shall be operated from multiple sets of linkages mounted on the leaving face of the dampers. [Control of the dampers shall be from a factory installed, two-position actuator.]
Access
A. The unit shall be provided with factory installed access sections located [upstream] [downstream] [upstream and downstream] of the supply air fan, as shown on the unit drawing. Access sections shall have hinged access doors on both sides of the section and shall have the same construction features as the rest of the unit.
Static Air Mixer (Air Blender)
A. A static air mixing device shall be factory installed between the outside/return air section and the filter section. The static air mixer shall be installed with proper upstream and downstream distances. The mixing device shall perform at face velocities from 500fpm through 2500fpm with no loss in mixing performance. The mixing device shall provide mixing and distribution of the outside and return air streams to minimize the threat of coil freeze-up during operation and to improve temperature control.
B. Acceptable manufacturers are Blender Products and Kees.
Sound Attenuator (RPE Only)
A. A sound attenuator section shall be provided as an integral part of the unit to attenuate fan noise at the source. The attenuator shall include a variable range of splitter thickness and air passages shall be provided to optimize acoustic performance and energy conservation. The section shall be perforated double-wall construction located downstream of the supply fan. Hinged access doors shall be provided on both sides of the section and shall have the same construction as the rest of the unit. [The sound attenuator shall have Tedlar mylar coating for moisture protection]. Combustion rating for the silencer acoustic fill shall not be greater than the following UL fire hazard classification:
Smoke Developed ........................................0
Tested in accordance with UL Test Procedure 723.
B. The attenuator rating shall be determined using the duct-to-reverberant room test method which provides for airflow in both directions through the attenuator in accordance with latest version of
Cat 219 63
ASTM specification E-477. Insertion Loss Ratings (ILR) shall be:
Octave Band at Center Frequency (Hz)
C. Manufacturer shall provide certified test data on dynamic insertion loss, self generated sound power levels, and aerodynamic performance for reverse and forward flow test conditions to the design professional in writing as least 10 days prior to the bid.
Discharge And Return Plenum Accessories
A. A supply air discharge plenum shall be provided. [The plenum section shall be lined with a perforated acoustic liner to enhance sound attenuation.] The plenum section shall have a [bottom] [side] discharge opening.
B. A combination burglar bar/safety grate shall be provided in the [bottom return air opening] [bottom supply air opening] [bottom return and supply air openings]. Burglar bar/safety grate shall be made of 3/4 in. diameter ground and polished steel shaft welded to a galvanized steel frame.
C. Isolation dampers shall be provided in the [bottom return air opening] [bottom supply air opening] [bottom return and supply air openings]. [A two-position actuator shall be provided to close the dampers when the fans are not running.]
Condensing Unit Section
A. RPE, RDE Evaporative Cooled Condenser
1. Condenser coils shall be multi-row and fabricated from 5/8 in. high efficiency copper tubing mechanically bonded to polymer, corrosion resistant, tube sheet supports. The condenser coil shall be removable for service without disas-sembling the unit.
2. At least four condenser fans shall be provided for back up protection. Condenser fans shall be direct drive, propeller type designed for low tip speed, vertical air discharge, and include service guards. Fan blades shall be constructed of cor-rosion resistant, reinforced polypropylene. Con-denser fan motors shall be severe-duty, externally protected, three-phase, non-reversing, totally enclosed type with permanently lubricated ball bearings.
3. Condenser fan capacity shall be controlled to allow compressor operation down to 45° F ambi-ent.
4. All wetted surfaces of the spray compartment shall be constructed of corrosion resistant stain-less steel. The sump can be separated into mul-tiple sections and each can be individually
removed without disassembling the unit. The entire sump is 2-dimensionally sloped to the drain and constructed of stainless steel. [A fully wired sump heater complete with thermostat control shall be provided.]
5. Removable mist eliminators are provided between the condenser coil and fans. Air intake shutters separate the sump from sunlight to pre-vent microbial growth.
6. A walk in service vestibule contains the electrical components and water spray pump for the con-densing unit. It also includes hinged access doors on both sides of the unit, two fully wired marine lights, a ventilation fan, electrical outlet, and manual shutter such that conditioned air can be used to cool the vestibule. Space shall be allowed for a field installed water treatment sys-tem including wall-mounted controller, control valves, and floor-mounted chemical tanks. The floor under the water pump, PVC tubing and water treatment system shall include a drain pan, for protection against water leaks, and a walking grate that is raised above the pan. [A fully wired 1.5KW unit heater shall be installed and wired complete with thermostat on-off con-trol.]
7. The spray system includes PVC tubing, [1.5 HP, size 76-100] [2 HP, size 110-150] pump, single field water connection, single field drain/ bleed connection and water treatment connections. The spray nozzles shall be removable, clog resistant and spray water across a 150° arc. The spray system shall include a [manually] [manual and solenoid] operated drain valve plus a float controlled solenoid that automatically maintains proper sump water levels.
8. [An electric sump heater shall be provided, including heat tape on all external piping.]
B. Reciprocating Compressors
1. Each unit shall have multiple, heavy-duty Cope-land Discus®, semi-hermetic, reciprocating com-pressors.
2. Each compressor shall include reversible, posi-tive displacement oil pump, suction and dis-charge line service valves, crankcase heater, high efficiency blocked suction unloading, and three-leg inherent motor overload protection.
3. Compressors shall be isolated with [resilient rub-ber isolators] [spring isolators with vibration elim-inators in the suction and discharge lines] to decrease noise transmission.
4. The unit shall have two independent refrigera-tion circuits. Each circuit shall be complete with a liquid line solenoid valve, low pressure control, [filter-drier] [replaceable core filter drier], liquid moisture indicator/sight-glass, thermal expan-sion valve, liquid line shutoff valve with charging port, a manual reset high pressure safety switch, high pressure relief device and pump down switch. The thermal expansion valve shall be
ILR 63 125 250 500 1000 2000 4000 8000
Standard
Attenuator7 9 22 28 29 29 18 12
Mylar
Coated6 10 20 16 14 18 13 12
64 Cat 219
capable of modulation from 100% to 25% of its rated capacity. Sight-glasses shall be accessible for viewing without disrupting unit operation.
5. Refrigeration capacity control shall be accom-plished with a combination of compressor cycling and high efficiency blocked suction unloading. All compressor capacity control staging shall be controlled by the factory installed main unit con-trol system.
6. [Constant air volume, zone temperature control - To maintain desired temperature control, the unit shall have a minimum of [four] [six] [eight] steps of capacity control.]
7. [Variable air volume, discharge temperature control - To maintain desired temperature con-trol, the unit shall have a minimum [six] [eight] steps of capacity control.]
C. Hot gas bypass control shall be factory installed on one [both] refrigerant circuits. Hot gas bypass control shall include a modulating hot gas bypass control valve, integral solenoid valve, all associated piping and be automatically operated by the units microprocessor control.
Roof Curb
A. A prefabricated 12-gauge galvanized steel, mounting curb, designed and manufactured by the unit manufacturer, shall be provided for field installation prior to unit shipment. The roof curb shall be a full perimeter type with complete perimeter support of the air handling section and rail support of the condensing section. Supply and return opening duct frames shall be provided as part of the curb structure allowing duct connections to be made directly to the curb prior to unit arrival. The curb shall be a minimum of 16" high and include a nominal 2" x 4" wood nailing strip. Gasket shall be provided for field mounting between the unit base and roof curb.
Controls
A. Each unit shall be equipped with a complete MicroTech® II microprocessor based control system. The unit control system shall include all required temperature and pressure sensors, input/output boards, main microprocessor and operator interface. The unit control system shall perform all unit control functions including scheduling, temperature control, static pressure control, alarms, unit diagnostics and safeties. All boards shall be individually replaceable for ease of service. All microprocessors, boards, and sensors shall be factory mounted, wired and tested.
B. The microprocessor shall be a stand-alone DDC controller not dependent on communications with any on-site or remote PC or master control panel. The microprocessor shall maintain existing set points and operate stand alone if the unit loses either direct connect or network communications. The microprocessor memory shall be protected from voltage fluctuations as well as any extended
power failures. All factory and user set schedules and control points shall be maintained in nonvolatile memory. No settings shall be lost, even during extended power shutdowns.
C. The main microprocessor shall support an RS-232 direct connection to a product service tool or a modem. A [BACnet IP] [BACnet MSTP] [LonWorks] communications port shall be provided for direct communication into the BAS network. [The controller shall be LonMark certified.]
D. All digital inputs and outputs shall be protected against damage from transients or wrong voltages. Each digital input and digital output shall be equipped with an LED for ease of service. All field wiring shall be terminated at a separate, clearly marked terminal strip.
E. The microprocessor memory shall be protected from all voltage fluctuations as well as any extended power failures. The microprocessor shall support an RS-232 direct connect from an IBM PC or 100% true compatible using MicroTech software. The microprocessor shall maintain existing set points and operate stand alone if the rooftop loses either direct connect or network communications.
F. The microprocessor shall have a built-in time schedule. The schedule shall be programmable from the unit keypad interface. The schedule shall be maintained in nonvolatile memory to insure that it is not lost during a power failure. There shall be one start/stop per day and a separate holiday schedule. The controller shall accept up to sixteen holidays each with up to a 5-day duration. Each unit shall also have the ability to accept a time schedule via BAS network communications.
G. [The unit shall include a night setback or setup function and a space sensor shall be provided by the manufacturer. The control contractor shall be responsible for wiring between the unit and space sensor. The sensor shall include a zone sensor with tenant override switch [and a heating and cooling set point adjustment (CAV-ZTC only.)]
H. User interface [UI]
1. The keypad/display character format shall be 20 characters x 4 lines. The character font shall be a 5 x 8 dot matrix. The display shall be a super twist liquid crystal display (LCD) with black char-acters on yellow background providing high visi-bility. The display form shall be in plain English coded formats. Lookup tables are not acceptable
2. The keypad shall be equipped with 8 individual touch-sensitive membrane key switches. All con-trol settings shall be password protected from changes by unauthorized personnel.
3. [Both a unit mounted and remote mounted UI shall be provided per unit. A unit-mounted switch brings either the unit mounted or remote mounted UI into control. The control contractor is responsible for wiring between the unit and the remote UI.]
Cat 219 65
• The maximum wiring distance to the remote UI is 1200 feet.
• Optical isolation shall protect the main unit con-troller from remote UI wiring problems
• The remote UI shall be provided with the same keypad/ display and have identical functionality to the unit mounted UI.
I. The display shall provide the following information:
1. Return, supply, outdoor and space air temperature
2. Duct and building static pressure- the control contractor is responsible for providing and installing sensing tubes
3. Supply and return fan status and airflow verification
4. Supply and return VFD speed
5. Outside air damper position and economizer mode
6. Cooling and heating and changeover status
7. Occupied, unoccupied, and dirty filter status
8. Date and time schedules
9. Up to 4 current alarms and 8 previous alarms with time and date
J. The keypad shall provide the following set points as a minimum:
1. Six control modes including off manual, auto, heat/cool, cool only, heat only and fan only
2. Four occupancy modes including auto, occu-pied, unoccupied and bypass (tenant override with adjustable duration).
3. Control changeover based on return air temper-ature, space temperature, network signal, out-door air temp (VAV with mod. heat).
4. Primary cooling and heating set point tempera-ture based on supply or space temperature
5. Night setback and setup space temp.
6. Cooling and heating control differential (or dead band).
7. Cooling and heating supply temperature reset options based on return air, outdoor air, or space air temperature Airflow (VAV,) network, or exter-nal (1-5 VDC) signal.
8. Reset schedule temperature.
9. High supply, low supply and high return air tem-perature alarm limits.
10.Ambient compressor and heat lockout temperatures.
11.Auto or manual lead lag method on compressors.
12.Compressor inter-stage timers duration.
13.Duct and building static pressure (opt.)
14.Duct static pressure reset based on network signal.
15.Return fan tracking (VaneTrol) settings that include minimum/maximum VFD speed with and without remote exhaust operation.
16.Minimum outdoor airflow reset based on Design-Flow direct OA volume measurement, external reset (1-5VDC,) percent of CFM capacity, and fixed outdoor damper position.
17.Economizer changeover based on enthalpy, dry bulb or network signal.
18.Current time and date.
19.Occupied/unoccupied time schedules with allowances for holiday/ event dates and duration
20.Three types of service modes including timers normal (all time delays,) timers fast (all time delays 20 seconds,) and normal
L. Open Communications Protocol - The unit control system shall have the ability to communicate to an independent Building Management System (BMS) through a direct [BACnet IP] [BACnet MSTP] [LonTalk] communication connection.
1. The independent BMS system shall have access to [quantity from specification] “read only” vari-ables and [quantity from specification] “read & and write” variables. Communications shall not require field mounting of any additional sensors or devices at the unit. The BMS system shall be capable of interacting with the individual rooftop controllers in the following ways:
• Monitor controller inputs, outputs, set points, parameters and alarms
• Set controller set points and parameters• Clear alarms• Reset the cooling and heating discharge air
temperature set point (VAV and CAV-DTC units)
• Reset the duct static pressure set point (VAV units)
• Set the heat/cool changeover temperature (VAV and CAV-DTC units)
• Set the representative zone temperature (CAV-ZTC units)
2. It will be the responsibility of the Systems Integrating Contractor to integrate the rooftop data into the BMS control logic and interface stations.
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