HVAC Guide Specifications
Packaged Rooftop Electric Cooling Unit WithOptional Electric Heat — Constant VolumeApplications
SizeRange:
18 to 25 Tons, Nominal (Cooling)
19 to 78 kW Nominal (Electric Heating)
Bryant ModelNumber:
551A
Part 1 — General
1.01 SYSTEM DESCRIPTION
Unit is an outdoor rooftop mounted, electrically controlledheating and cooling unit utilizing scroll hermetic compressorswith crankcase heaters for cooling duty and gas combustionheat for heating duty. Supply air shall bedischarged downward or horizontally, as shown on contractdrawings.
1.02 QUALITY ASSURANCE
A. Unit shall well exceed the energy efficiency requirementsof ASHRAE standard 90.1-2001. Unit shall be EnergyStar qualified.
B. Unit shall be rated in accordance with ARI Standards 270and 360 and all units shall be designed in accordancewith UL Standard 1995.
C. Unit shall be designed to conform to ASHRAE 15.
D. Unit shall be UL and UL, Canada, tested and certified inaccordance with ANSI Z21.47 Standards as a totalpackage.
E. Roof curb shall be designed to conform to NRCA Standards.
F. Insulation and adhesive shall meet NFPA 90A requirementsfor flame spread and smoke generation.
G. Unit casing shall be capable of withstanding 500-hour saltspray exposure per ASTM B117 (scribed specimen).
H. Unit shall be manufactured in a facility registered to ISO9001:2000.
1.03 DELIVERY, STORAGE, AND HANDLING
Unit shall be stored and handled per manufacturer’srecommendations.
Part 2 — Products
2.01 EQUIPMENT (STANDARD)
A. General:
The 551A unit shall be a factory assembled, single-pieceheating (if equipped) and cooling unit. Contained withinthe unit enclosure shall be all factory wiring, piping, controls,refrigerant charge (R-22), and special featuresrequired prior to field start-up.
B. Unit Cabinet:
1. Constructed of galvanized steel (G90 — 1.8 oz. ofzinc per square foot of sheet metal), bonderized andprimer-coated on both sides and coated with a bakedpolyester thermosetting powdercoating finish on theouter surface.
2. Indoor blower compartment interior surfaces shall beinsulated with a minimum 1/2-in. thick, 1 lb densityfiberglass insulation. Fiberglass insulation shall bebonded with a thermosetting resin (8 to 12% byweight nominal, phenol formaldehyde typical), andcoated with an acrylic or other material that meetsthe NFPA 90 flame retardance requirements and hasan ‘‘R’’ Value of 3.70. Aluminum foil-faced fiberglassinsulation shall be used in the gas heatcompartment.
3. Cabinet panels shall have minimum 1/2-in. thick,1.5-lb. density insulation. Cabinet panels shall beeasily removable for servicing.
4. Filters shall be accessible through an access panel.
5. Holes shall be provided in the base rails (minimum14 gage) for rigging shackles and level travel andmovement during overhead rigging operations.
6. Fork lift slots shall be available from two sides of theunit (end and side).
7. Unit shall contain a sloped drain pan, to preventstanding water from accumulating. Pan shall be fabricatedof epoxy powder coated steel.
C. Fans:
1. Indoor blower (evaporator fan):
a. Centrifugal supply air blower shall have pillow-blockball bearings and adjustable belt drive.Blower assembly shall slide out of unit forservicing.
b. Fan wheel shall be made from steel with a corrosionresistant finish. It shall be a dynamically balanced,double-inlet type with forward-curvedblades.
c. The indoor fan system (blower wheels, motors,belts, and both bearings) shall slide out for easyaccess.
2. Condenser fans shall be of the direct-driven propellertype, with corrosion-resistant blades riveted to corrosion-resistant steel supports. They shall be dynamicallybalanced and discharge air upwards.Condenser fan motors shall be totally enclosed andbe of a shaft down design.
D. Compressor(s):
1. Fully hermetic, scroll type, internally protected.
2. Factory spring-shock mounted and internally springmounted for vibration isolation.
3. On electrically and mechanically independent refrigerantcircuits.
4. Reverse rotation protection capability.
5. Crankcase heaters shall only be activated duringcompressor OFF mode.
E. Coils:
1. Standard evaporator and condenser coils shall havecopper or aluminum plate fins mechanically bondedto seamless internally grooved copper tubes with alljoints brazed.
2. Coils shall be leak tested at 150 psig (1034 kPa) andpressure tested at 450 psig (3103 kPa).
3. Optional pre-coated aluminum-fin coils shall have adurable epoxy-phenolic coating to provide protectionin mildly corrosive coastal environments. Coatingshall be applied to the aluminum fin stock prior to thefin stamping process to create an inert barrierbetween the aluminum fin and copper tube. Epoxy-phenolicbarrier shall minimize galvanic actionbetween dissimilar metals.
4. Copper-fin coils shall be constructed of copper finsmechanically bonded to copper tubes and coppertube sheets. Galvanized steel tube sheets shall notbe acceptable. A polymer strip shall prevent coilassembly from contacting the sheet metal coil pan tominimize potential for galvanic corrosion betweencoil and pan. All copper construction shall provideprotection in moderate coastal environments.
5. E-Coated aluminum-fin coils shall have a flexibleepoxy polymer coating uniformly applied to all coilsurface areas without material bridging between fins.Coating process shall ensure complete coil encapsulation.Color shall be high gloss black with gloss —60 deg of 65 to 90% per ASTM D523-89. Uniform dryfilm thickness from 0.8 to 1.2 mil on all surface areasincluding fin edges. Superior hardness characteristicsof 2H per ASTM D3363-92A and cross-hatchadhesion of 4B-5B per ASTM D3359-93. Impactresistance shall be up to 160 in./lb (ASTM D2794-93). Humidity and water immersion resistance shallbe up to minimum 1000 and 250 hours respectively(ASTM D2247-92 and ASTM D870-92). Corrosiondurability shall be confirmed through testing to be noless than 1000 hours salt spray per ASTM B117-90.Coil construction shall be aluminum fins mechanicallybonded to copper tubes.
6. E-Coated copper-fin coils shall have a flexible epoxypolymer coating uniformly applied to all coil surfaceareas without material bridging between fins. Coatingprocess shall ensure complete coil encapsulation.Color shall be high gloss black with gloss — 60 degof 65 to 90% per ASTM D523-89. Uniform dry filmthickness from 0.8 to 1.2 mil on all surface areasincluding fin edges. Superior hardness characteristicsof 2H per ASTM D3363-92A and cross-hatchadhesion of 4B-5B per ASTM D3359-93. Impactresistance shall be up to 160 in./lb (ASTM D2794-93). Humidity and water immersion resistance shallbe up to minimum 1000 and 250 hours respectively(ASTM D2247-92 and ASTM D870-92). Corrosiondurability shall be confirmed through testing to be noless than 1000 hours salt spray per ASTM B117-90.Coil construction shall be copper fins mechanicallybonded to copper tubes with copper tube sheets.Galvanized steel tube sheets shall not be acceptable.A polymer strip shall prevent coil assembly from contactingsheet metal coil pan to maintain coating integrityand minimize corrosion potential between coiland pan.
F. Refrigerant Components:
Each refrigerant circuit shall include:
1. Thermostatic expansion valve (TXV) with removablepower element.
2. Filter driers.
3. Gage port and connections on suction anddischarge.
G. Filter Section:
Standard filter section shall consist of factory-installed2-in. thick throwaway fiberglass filters.
H. Controls and Safeties:
1. Electro-Mechanical Control:
a. Economizer control (optional).
b. Capacity control (2-step).
c. Unit shall be complete with self-contained lowvoltagecontrol circuit.
2. Safeties:
a. Unit shall incorporate a solid-state compressorlockout which provides optional reset capability atthe space thermostat, should any of the followingsafety devices trip and shut off compressor:
1) Compressor lockout protection provided foreither internal or external overload.
2) Low-pressure protection.
3) Freeze protection (evaporator coil).
4) High-pressure protection (high pressure switchor internal).
I. Operating Characteristics:
1. Unit shall be capable of starting and running at 125 Fambient outdoor temperature per maximum load criteriaof ARI Standard 360.
2. Unit with standard controls will operate in coolingdown to an outdoor ambient temperature of 40 F.
3. Size 18 and 20 ton units shall have 3 fully independentrefrigerant circuits to allow for 33% capacity percircuit.
J. Electrical Requirements:
All unit power wiring shall enter unit cabinet at a singlelocation.
NOTE: On 208/230 v units using 75-kW heaters, separatewiring is required.
K. Motors:
1. Compressor motors shall be cooled by refrigerantgas passing through motor windings and shall haveline break thermal and current overload protection.
2. All fan motors shall have permanently lubricated,sealed bearings and inherent automatic-reset thermaloverload protection or manual reset calibratedcircuit breakers.
3. All indoor-fan motors 5 hp and larger shall meet theminimum efficiency requirements as established bythe Energy Policy Act of 1992 (EPACT), effectiveOctober 24, 1997.
L. Special Features:
Certain features are not applicable when the featuresdesignated * are specified. For assistance in amendingthe specifications, contact your local Bryant Sales Office.
1. Full Perimeter Roof Curbs (Horizontal and Vertical):
a. Formed of 14-gage galvanized steel with woodnailer strip and shall be capable of supportingentire unit weight.
b. Permits installing and securing ductwork to curbprior to mounting unit on the curb.
c. Retrofit roof curb kit shall be available for fit up toexisting Bryant roof curbs.
*2. Integrated Economizers:
a. Integrated integral modulating type capable ofsimultaneous economizer and compressoroperation.
b. Available as a factory-installed option in verticalsupply/return configuration only. (Available as afield-installed accessory for dedicated horizontaland/or vertical supply return configurations.)
c. Includes all hardware and controls to providecooling with outdoor air.
d. Equipped with low-leakage dampers, not toexceed 2% leakage at 1 in. wg pressuredifferential.
e. Capable of introducing up to 100% outdoor air.
f. EconoMi$er IV shall be equipped with a barometricrelief damper.
g. Designed to close damper(s) during loss-of-powersituations with spring return built intomotor.
h. Dry bulb outdoor-air temperature sensor shall beprovided as standard. Outdoor air sensor setpoint is adjustable and shall range from 40 to100 F. For the EconoMi$er IV, the return air sensor,indoor enthalpy sensor, and outdoor enthalpysensor shall be provided as field-installed accessoriesto provide enthalpy control, differentialenthalpy control, and differential dry bulb temperaturecontrol.
i. EconoMi$er IV Controller shall use a mixed airthermistor mounted on the evaporator fan housingto control EconoMi$er IV operation to a supplyair temperature of 55 F.
j. The EconoMi$er IV shall have a gear-driven parallelblade design.
k. EconoMi$er IV Controller shall provide control ofinternal building pressure through its accessorypower exhaust function. Factory set at 100%, witha range of 0% to 100%.
l. EconoMi$er IV Controller Occupied Minimum
Damper Position Setting maintains the minimumairflow into the building during occupied periodproviding design ventilation rate for full occupancy(damper position during heating). A remotepotentiometer may be used to override the setpoint.
m. EconoMi$er IV Controller Unoccupied MinimumDamper Position Setting — The EconoMi$er IVdampers shall be completely closed when the unitis in the occupied mode.
n. EconoMi$er IV Controller IAQ/DCV control modulatesthe outdoor-air damper to provide ventilationbased on the optional 2 to 10 vdc CO2 sensorinput.
o. Compressor lockout sensor (opens at 35 F,closes at 50 F).
p. Actuator shall be direct coupled to economizergear, eliminating linkage arms and rods.
q. Control LEDs:
1) When the outdoor-air damper is capable ofproviding free cooling, the “Free Cool” LEDshall illuminate.
2) The IAQ LED indicates when the module is onthe DCV mode.
3) The EXH LED indicates when the exhaust fancontact is closed.
r. Remote Minimum Position Control — A field-installedaccessory remote potentiometer allowsthe outdoor-air damper to be opened or closedbeyond the minimum position in the occupiedmode for modified ventilation.
*3. Barometric Relief Damper Package:
a. Package shall include damper, seals, hardware,and hoods to relieve excess internal pressure.
b. Damper shall close due to gravity upon unitshutdown.
*4. Power Exhaust:
Package shall include an exhaust (centrifugal style)fan, 1 Hp 208-230, 460 v (factory-wired for 460 v)direct-drive motor, and damper for vertical flow unitswith economizer to control over-pressurization ofbuilding.
*5. Thermostats and Subbases:
Thermostats and subbases shall provide stagedheating and cooling in addition to automatic (or manual)changeover and fan control.
6. Electronic Programmable Thermostat:
Unit shall be capable of using deluxe full-featuredelectronic thermostat.
7. Convenience Outlet:
Outlet shall be factory-installed and internallymounted with an externally accessible 115-v, 15 ampGFI, female receptacle with hinged cover. A stepdown transformer shall be included so no additionalwiring is necessary.
8. Non-Fused Disconnect Switch:
Switch shall be factory-installed, internally mounted,NEC and UL approved. Non-fused switch shall provideunit power shutoff. Shall be accessible from outsidethe unit and shall provide power off lockoutcapability.
9. Electric Heater Package:
a. Fully assembled for installation. The packagesare designed in accordance with UL safety standards1995 and listed by ETL. Heater constructionapproved by UL 5306.
b. Heater element open coil resistance wire, nickelchromealloy, 0.29 inches inside diameter, strungthrough ceramic insulators mounted on metalframe. Coil ends are staked and welded to terminalscrew slots.
c. Heater assemblies are provided with integral fusingfor protection of internal heater circuits notexceeding 48 amps each.
d. Auto reset thermo limit controls, magnetic heatercontactors (24 v coil) and terminal block allmounted in electric heater control box (minimum18 ga. Galvanized steel) attached to end ofheater assembly.
10. Hail Guard, Condenser Coil Grille:
Grille shall protect the condenser coil from hail, flyingdebris, and damage by large objects without increasingunit clearances.
11. Horizontal Kit:
Horizontal kit shall contain all the necessary hardwareto convert a vertical airflow unit to a horizontalairflow unit.The unit shall also be available as a horizontal airflowunit directly from the factory.
12. Return Air Smoke Detector:
The smoke detector shall send input to the controllerto shut down the unit in case smoke is detected. Thesmoke detector shall be factory installed in the returnair section or shall be available as a field-installedaccessory.
13. Two-Position Damper:
The damper shall admit up to 25% outdoor air andshall close upon shutdown. The package shallinclude a single-blade damper and motor.
14. Manual Damper:
The damper shall have a manually adjustable outsideair intake for up to 33% outside air.
15. Motor/Drive Combinations:
Low, mid-low, mid-high and high motor/drive combinationsare available to match evaporator fan performancewith each application.
16. Outdoor Air Enthalpy Sensor (EconoMi$er IV):
The outdoor air enthalpy sensor is used to senseoutdoor air enthalpy for the EconoMi$er IV device.The outdoor air enthalpy sensor, in conjunction withthe standard outdoor air temperature sensor, shallbe used with the EconoMi$er IV device to provideoutdoor enthalpy. Outdoor air enthalpy shall be calculatedby the EconoMi$er IV device from the outdoorair temperature and humidity readings. Whenthe outdoor air enthalpy sensor is installed, theEconoMi$er IV can perform Outdoor Air Enthalpycontrol. With the additional installation of an accessoryreturn air temperature sensor and return airenthalpy sensor, differential enthalpy control canalso be performed.
17. Return Air Enthalpy Sensor (EconoMi$er IV):
The return air enthalpy sensor is used to sensereturn air enthalpy for the EconoMi$er IV device. Thereturn air enthalpy sensor, in conjunction with theaccessory return air temperature sensor, shall beused with the EconoMi$er IV device to provide returnair enthalpy. Return air enthalpy shall be calculatedby the EconoMi$er IV device from the return air temperatureand humidity readings. With the additionalinstallation of an accessory return air temperaturesensor and outdoor air enthalpy sensor, differentialenthalpy control can also be performed.
18. Return Air Temperature Sensor (EconoMi$er IV):
The return air temperature sensor is used to sensereturn air temperature for the EconoMi$er IV device.When the return air temperature sensor is installed,the EconoMi$er IV can perform Differential Temperaturecontrol. The return air temperature sensor, inconjunction with the accessory return air enthalpysensor, shall be used with the EconoMi$er IV deviceto provide return air enthalpy. Return air enthalpyshall be calculated by the EconoMi$er IV devicefrom the return air temperature and humidity readings.With the additional installation of an accessoryreturn air enthalpy sensor and outdoor air enthalpy sensor, differential enthalpy control can also beperformed.
19. Indoor Air Quality (CO2) Room Sensor (EconoMi$erIV):
Sensor shall have the ability to provide demand ventilationcontrol through the EconoMi$er IV. The IAQsensor shall be wall mounted with an LED display inparts per million. The set point shall have adjustmentcapability.
20. Return Air CO2 Sensor (EconoMi$er IV):
Sensor shall have the ability to provide demand ventilationcontrol through the EconoMi$er IV. The IAQsensor shall be duct mounted. The set point shallhave adjustment capability.
21. Supply Air Smoke Detector:
The smoke detector shall send input to the controllerto shut down the unit in case smoke is detected. Thesmoke detector shall be factory-installed in the supplyair section or shall be available as a field-installedaccessory.
22. Supply and Return Air Smoke Detector:
The smoke detector shall send input to the controllerto shut down the unit in case smoke is detected. Thesmoke detector shall be factory installed in the supplyand return air sections or shall be available as afield-installed accessory.
23. Condensate Overflow Switch:
The condenser overflow switch shall close when thecondensate level in the pan rises above switch.
24. Hinged Panel Option:
Hinged panel option provide hinged access panelsfor the filter, compressor, evaporator fan, and controlbox areas. Filter hinged panels permit tool-less entryfor changing filters. Each hinged panel is permanentlyattached to the rooftop unit.