50XJ Guide Specifications, 50 to 100 Tons

50XJ Guide Specifications, 50 to 100 Tons

HVAC Guide Specifications

Indoor Packaged Water-Cooled Variable AirVolume Cooling Unit

Size Range:

50 to 100 Tons, Nominal Cooling

Carrier Model Number:


Part 1 — General


Indoor, water-cooled, vertical discharge, microprocessorcontrolled variable air volume (VAV), coolingand heating unit utilizing scroll type compressors forcooling duty. Units shall discharge supply air verticallyupward or horizontally through an acoustic dischargeplenum as shown on the contract drawings.Each unit shall be completely factory assembled andtested and shall ship in one piece.


A. Unit shall be rated in accordance with AHRI Standard340/360, and tested to AHRI Standard 260.

B. Unit shall be designed to conform to ANSI/ASHRAE 15, latest revision, UL Standard 1995,and National Electrical Code.

C. Unit shall be ETL Listed to US and Canadian Standardsfor Safety, as a total package.

D. Insulation and adhesive shall meet NFPA 90Arequirements for flame spread and smokegeneration.

E. Unit shall be factory run tested to include as a minimuma compressor bump over test and full electricaland control circuit test.


The manufacturer shall warranty equipment for aperiod of 12 months from start-up or 18 monthsfrom shipping (whichever occurs first).


Unit shall ship in one piece and be stored and handledper manufacturer’s recommendations.

Part 2 — Products


A. General:

Factory-assembled, single-piece water-cooled coolingunit with optional economizer and heatingcapability. Contained within the unit enclosure shallbe all factory wiring, water and refrigerant piping,refrigerant charge (R-410A), operating oil charge,multiple refrigerant circuits on individual condensers,microprocessor-based control system for standaloneor building network operation and associatedhardware, and all special features required prior tofield start-up.

B. Unit Cabinet:

1. Constructed of galvanized steel, bonderized andcoated with a baked polyester thermosettingpowder coating gray finish on the outer surface.Unit frame shall be post and panel constructionso any access panel may be removed for servicewithout impacting the structural integrity of theunit. Base frame members shall be constructedof minimum of 10-gage steel constructed toprovide a rigid mounting base and structuralsupport and to provide adequate strength forthe unit to be lifted and moved by the base rail.All other unit support members shall be a minimumof 12-gage steel.

2. Unit casing shall be capable of withstandingASTM Standard B117 500-hour salt spray test.

3. All standard service access panels shall haveperson-size insulated access doors for easyaccess to the control box, fan and motor, compressorsand other areas requiring servicing.Each door shall seal against a neoprene rubbergaskets to prevent air leakage, doors shall besecured by quarter turn latches requiring onlyone tool for service entry and be equipped withrecessed lifting handles to permit easy removaland safe handling during servicing. Access panelsshall not weigh more than 50 pounds and becapable of being removed by one person.Removable access panels shall be provided withrecessed style lifting handles. All exterior panelsshall be a minimum of 19-gage sheet metal andbe painted gray.

4.Interior cabinet surfaces within the evaporatorsection shall be insulated with minimum 1-in.11/2-pound density flexible fire-retardant fiberglassblanket. Units with the double wall optionshall be covered with a solid full minimum20-gage sheet metal internal liner in all areasdownstream of the cooling coil with no exposedinsulation. Surfaces between the cooling coiland fan, which have rough surfaces or openingswhich can not be wiped clean and foil facedstyle insulation, are not acceptable.

5. Interior cabinet surfaces within compressor andcondenser section shall be lined with minimum1-in. thick 11/2-pound density acoustical insulation.Panel construction shall protect edges ofinsulation damage during removal of panels.

6. Insulation shall be applied by means of adhesionusing a water reducible adhesive sprayedonto interior surface. Adhesive shall maintain asatisfactory adhesion and cohesion within thetemperature range of –20 to 180 F and haveexcellent resistance to water and water vaporwhen cured.

7. Unit shall contain a dual sloped drain pan toprevent standing water from accumulating witha minimum slope of 1/8-in. per foot. Pan shallbe fabricated of type 303 stainless steel and beinsulated with a minimum of 1-in. 11/2 pounddensity insulation. Unit shall contain a factory-installedand internally trapped main condensatedrain. Main condensate drain shall beextended with the connection made at the unitside panel and the trap shall be removable forcleaning.

8. Units shall be equipped with lifting lugs to facilitateoverhead rigging. Lugs shall be constructedof minimum 1-in. structural steel with liftingholes sized for cables or chain hooks.

9. Unit shall be provided with factory selectedvibration isolation pads to place under the unitby the installing contractor.

C. Fan Section:

Evaporator fan shall consist of a single fan, mediumpressure, class II blower, mounted on a complete fansled assembly consisting of blower, motor, motoradjusting plate and drive. Assembly shall be completelyspring mounted and fan discharge shall beisolated from the unit casing by flexible connectionto prevent transmission of vibration to theunit assembly. Fan assembly shall be secured byshipping brackets during shipping to prevent internaldamage.

1. Fan shall be double-width, double-inlet centrifugalbelt driven forward-curve type with singleoutlet discharge. Fan wheel and scroll shall beconstructed of steel with corrosion resistant finishand shall be statically and dynamicallybalanced.

2. Fan shall be belt driven with fixed-pitch motorand fan pulley, with multiple matched belts,drive shall be selected for 110% of motorhorsepower and to provide maximum staticcapability in stable fan operation and whenapplied with Variable Frequency Drive (VFD).

3. Fan shall be mounted on a structural steel sledwith flexible outlet connection consisting of canvastransitions.

4. Fan shaft bearing shall be sealed pillow-blocktype ball bearing with lubrication provisions andshall have a L50 life of 200,000 hours atdesign operating conditions in accordance withANSI B3.15. Bearing size shall not be smallerthan the main fan shaft diameter.

5. Fan shaft shall be solid fan shaft constructionand constant diameter.

6. Motor adjusting plate shall have screw typeadjustment to allowing proper belt tensioning.

7. Unit shall be equipped with 5-in. spring vibrationisolators, each with approximately 2-in.static deflection.

D. Compressors:

1. Shall be hermetic scroll type only and shall belocated for easy servicing.

2. Shall be direct drive, 3600 rpm, internally protected,suction gas cooled motor with internalspring and external rubber in shear vibrationisolation.

3. Each equipped with compressor overload protection,oil sight glass, anti-slugging protection,operating oil charge, crankcase heater to preventrefrigerant migration to the compressor.

4. The number and size of compressors shall be asshown on the drawings.

E. Condensers:

1. Condensers shall be of the shell and tubetype with removable condenser heads for cleaning.Each condenser shall serve only onecompressor.

2. Tubes shall be seamless with no internal joints.

3. Condensers shall have a maximum workingpressure of 150 psig on the waterside (400 psigoptional).

F. Evaporator Coil:

1. Shall be minimum 4-row 3/4-in. tube with intertwinedcircuiting constructed of aluminum finsmechanically bonded to seamless copper tubes.

2. Full-face active type during full and all part loadconditions.

3. Coils shall be leak tested at 150 psig and pressuretested at 450 psig.

G.Supply Fan Capacity Control/Variable FrequencyDrive:

Variable Frequency Drive (VFD) shall include:

1. Factory-installed VFD motor control device,provided with a NEMA Type 1 enclosure, andfactory-mounted, wired and tested. The VFDshall control motor speed to maintain setpoint static pressure at the supply duct sensorlocation.

2. Digital display keyboard module, mounted onunit control panel.

3. Factory-mounted duct pressure sensingcontroller:

Differential pressure transducer, 2 to 10 vdcoutput to unit control module, with adjustableset point range (0.0 to 5.0 in. wg), adjust viaunit control keypad.

4. Low pressure reference tube factory installed.

H. Refrigerant Components:

Unit shall be equipped with four independent refrigerantcircuits, one for each compressor, eachcontaining:

1. Liquid line charging port.

2. Filter drier.

3. Moisture indicating sight glass which shall beaccessible for charging and viewing with theunit in operation.

4. Thermostatic expansion valve with externallyequalizer connection located out of the supplyairstream.

5. Fusible plug with service valve option.

6. Condenser pressure relief valve.

7. Frost protection control on each compressorcircuit.

I. Filter Section:

Filter section shall consist of 4-in. thick, disposablefiberglass filters of commercially available sizes. Unitshall have a minimum MERV 6 rating per ASHRAEStandard 52. Filter face velocity shall not exceed550 fpm. All filters shall be removable from the rearof the unit. Filter holding tracks shall have filterremoval access and filter retainers shall maintain aseal of the filters to the coil track to prevent airbypass.

J. Controls, Safeties, and Diagnostics:

1. Controls:

a. Control shall be accomplished through theuse of a factory-installed, microprocessor-basedcontrol system and associated electronicand electrical hardware. Controlsystem shall determine control sequencesthrough monitoring the following operationalvariables:

1) Day and time.

2) Schedule (Unoccupied/Occupied).

3) Set points (Unoccupied/Occupied,Economizer, Duct Pressure, others).

4) Space temperature.

5) Outdoor-air temperature (field-installedoption).

6) Unit supply-air temperature.

7) Unit return-air or mixed-air temperature.

8) Supply-air fan status.

9) Economizer position.

10) Accessory and/or field-supplied sensors,function switches and/or signals.

b. Controls shall be capable of performing thefollowing functions:

1) Capacity control based on discharge-airtemperature and compensated by rateof change of return-air temperature(VAV [variable air volume]). Capacitycontrol shall be accomplished throughthe use of compressor staging.

2) Perform a quick test to check the statusof all input and output signals to thecontrol system using diagnostic displaymodule.

3) Control of integrated economizer operation,based on unit supply-airtemperature.

4) Supply fan volume control shall controloutput from a variable frequency drive tomaintain duct static pressure at user-configuredset point.

5) Heating control shall provide space temperaturecontrol for unoccupied periodheating, morning warm-up sequenceand occupied period heating (whenconfigured).

6) Alarms: Control shall continuously monitorall sensor inputs and control outputsto ensure safe and proper systemoperation. Alarms shall be initiatedwhen unit control detects that a sensorinput value is outside its valid range (indicatinga defective device or connectionthat prevents full unit operation), that anoutput has not functioned as expected,or that a safety device has tripped.

7) Timed override function shall permit asystem in Unoccupied mode to bereturned to Occupied mode for a user-configuredperiod of 1, 2, 3 or 4 hoursby pressing the override button on thefront of the space temperature sensor.

8) Nighttime free cooling (NTFC) shall startthe supply fan and open the economizeron cool nights to pre-cool the buildingstructure mass using only outdoor air.Function shall be restricted to operationabove a user-configured low lockouttemperature set point.

9) Modulating power exhaust control shallmodulate capacity of exhaust fan systemin response to building static pressureat user-configured set point. Powerexhaust fan operation shall be interlockedwith supply fan status.

10) Indoor air quality (IAQ) mode shall admitfresh outdoor air into the space wheneverspace air quality sensors detectunsuitable space conditions, by overridingeconomizer minimum damper position.The IAQ mode shall be permittedonly during occupied periods. Controlshall permit user to configure for threepriority levels: sense and alert but noventilation action; ventilate only whencomfort conditions are satisfied; ventilateimmediately upon demand. IAQmode shall also provide control forreheat via auxiliary heating coil duringventilation (when configured).

11) Outdoor air control (OAC) function shallmaintain a minimum quantity of outdoorairflow into an occupied space. TheOAC mode shall be available only duringan occupied period.

12) Dehumidification: Dehumidificationfunction shall override comfort conditionset points to deliver cooler air into thespace and satisfy a user-configuredhumidity set point at the space or returnair humidity sensor.

13) Supply Air Temperature Set PointReset: Control shall automatically resetthe unit supply air temperature set pointon VAV models from space temperature,at user-configured rate and limit.Control shall also reset supply air temperatureset point via external 2 to10 vdc signal representing 0° to 20 Frange of reset. Control shall respond tohigher of either reset if both are active.

14) Condenser-head pressure control shallmaintain correct head pressure with anentering water temperature as low as40 F.

15) Hydronic heating coil control shall modulatea control valve in a stream orhydronic heat system to maintain spacetemperature at user-configured setpoints. Analog output shall be 0 to10 vdc signal.

16) Keypad/Display Module (BACview6): Module shall provide hardware necessaryfor human interface with the unitintegrated system controls. Module shallcontain a keypad and display for interactivecommunication. Display shall befour-line, backlit alphanumeric liquidcrystal display (LCD). Each line of theLCD shall display up to 40-character(with expanded scrolling displaycapability).

2. Safeties:

Unit components shall be equipped with the followingprotections:

a. Overcurrent using internal or external compressoroverload modules (shuts down individualcompressor).

b. Crankcase heaters.

c. High-pressure switch (shuts down individualcompressor, automatic reset type).

d. Low-pressure switch (shuts down individualcompressor, automatic reset type).

e. Check filter switch (optional).

f. High duct static switch.

3. Diagnostics:

a. BACview display module shall be capable ofindicating a safety lockout condition (alarm)through an expandable scrolling display.

b. BACview display module shall also becapable of indicating an alert conditionwhich does not lock out the unit, butinforms the system monitor of a conditionwhich could be detrimental to either the unitor the comfort of the occupants if allowed tocontinue.

c. BACview module must also be capable ofdisplaying outputs of microprocessor-controlled“quick test” to verify operation ofevery thermistor, actuator motor, and fan.

K. Operating Characteristics:

1. Unit shall be capable of starting and running at115 F entering condenser water temperaturemaximum load criteria of AHRI Standard 340/360.

2. Unit shall be capable of mechanical coolingoperation down to 50 F entering condenserwater temperature without head pressurecontrol and down to 40 F with head pressurecontrol.

3. Provides multi-stage cooling capability.

L. Motors:

1. Compressor motors shall be cooled by suctiongas passing over motor windings.

2. Evaporator blower motor shall be of the3-phase, NEMA rated, open drip-proof (ODP),ball bearing type, premium efficiency. Motorshall be compatible with variable frequencydrive (VFD). Motor horsepower shall be asshown on contract drawings to meet requiredtotal static pressure.

M. Electrical Requirements:

All unit power wiring shall enter unit cabinet at a singlelocation. Individual fusing for each motor shallprotect branch circuits for all motor loads within theunit. Main power connections to the unit shall be toa terminal block of adequate size for easy connectionof field power connections. Low voltage connectionsfor control and network communicationsshall be to factory mounted and labeled terminalstrips.

N. Special Optional Features:

1. Waterside integrated economizer.

2. Bypass switch for VFD (option).

3. Filter options: Unit shall be factory equippedwith high-efficiency pleated filters having thefollowing characteristics:

a. Efficiency of no less than 65% (85%) basedon testing per ASHRAE Standard 52.

b. Minimum average arrestance of 90%.

4. Non-Fused Disconnect: A non-fused electricaldisconnect for main unit power shall be factoryinstalled. The disconnect shall be an interlockingtype.

5. High waterside pressure condenser options.

6. Water flow switch.

7. Space Temperature Sensor (T-55): The T-55space temperature sensor (for CV applications)shall monitor space temperature. Device shallbe suited for wall mounting in the occupiedspace. The T-55 sensor shall also include abutton used to initiate Unoccupied Overridefunction.

8. Provide an extra set of the following:

a. Evaporator fan drive belts as required foroperation at horsepower requirements ofunit as indicated on the contract drawings.

b. Filters for replacement before building isturned over to owner.

9. Extended grease lines, all bearing grease fittingsshall have a grease connection brought to acommon point on the outside of the unit.

10. Compressor service valves.

11. Two-position condenser isolation valve.

12. Phase loss, low voltage protection.

13. Discharge plenum.

14. Fire and smoke shutdown.

15. Water regulating valve.

16. System control option.