Carrier Air Conditioner Operation And Service Manual

Also see for Air Conditioner: Owner's guide Owner's manual

67Consult application data section in the Product Data litera-ture and job design requirements to determine flow rate re-quirements for a particular installation.Table 36 — Nominal and Minimum CoolerFluid Flow RatesLEGEND*Nominal flow rates required at ARI conditions are 44 F (6.7 C) leaving-fluidtemperature, 54 F (12.2 C) entering-fluid temperature, 95 F(35 C) ambient.Fouling factor is .00001 ft2 ⋅ hr ⋅ F/Btu (.000018 m2 ⋅ K/W).NOTES:1. Minimum flow based on 1.0 fps (0.30 m/s) velocity in cooler without specialcooler baffling.2. Minimum Loop Volumes:Gallons = V x ARI Cap. in tonsLiters = N x ARI Cap. in kWOperation Sequence — During unit off cycle, crank-case heaters are energized. If ambient temperature is below36 F (2 C), cooler heaters (if equipped) are energized.The unit is started by putting the ENABLE/OFF/REMOTECONTACT switch in ENABLE or REMOTE position. Whenthe unit receives a call for cooling (either from the internalcontrol or CCN network command or remote contact closure),the unit stages up in capacity to maintain the cooler fluid setpoint. The first compressor starts 11/2 to 3 minutes after the callfor cooling.The lead circuit can be specifically designated or randomlyselected by the controls, depending on how the unit is fieldconfigured (for 040-070 sizes, Circuit A leads unless anaccessory unloader is installed on Circuit B). A field configura-tion is also available to determine if the unit should stage upboth circuits equally or load one circuit completely beforebringing on the other.When the lead circuit compressor starts, the unit starts witha pumpout routine. On units with the electronic expansionvalve (EXV), compressor starts and continues to run with theEXV at minimum position for 10 seconds to purge the refriger-ant lines and cooler of refrigerant. The EXV then moves to23% and the compressor superheat control routine takes over,modulating the valve to feed refrigerant into the cooler.On units with thermostatic expansion valve (TXV)(30GTN,R and 30GUN,R 040,045 units with brine option),head pressure control is based on set point control. When thelead compressor starts, the liquid line solenoid valve (LLSV) iskept closed for 15 seconds by a time delay relay. The micropro-cessor stages fans to maintain the set point temperature speci-fied by the controller. There is no pumpout sequence duringshutdown of TXV controlled chillers.On all other units (EXV units), the head pressure is con-trolled by fan cycling. The desired head pressure set point isentered, and is controlled by EXV position or saturated con-densing temperature measurement (T3 and T4). For proper op-eration, maintain set point of 113 F (45 C) as shipped from fac-tory. The default head pressure control method is set point con-trol. The head pressure control can also be set to EXV controlor a combination of the 2 methods between circuits.For all units, if temperature reset is being used, the unit con-trols to a higher leaving-fluid temperature as the building loadreduces. If demand limit is used, the unit may temporarily beunable to maintain the desired leaving-fluid temperature be-cause of imposed power limitations.On EXV units, when the occupied period ends, or when thebuilding load drops low enough, the lag compressors shutdown. The lead compressors continue to run as the EXV clos-es, and until the conditions of pumpout are satisfied. If a faultcondition is signaled requiring immediate shutdown, pumpoutis omitted.Loading sequence for compressors is shown in Tables 5Aand 5B.Refrigerant CircuitLEAK TESTING — Units are shipped with complete operat-ing charge of refrigerant R-22 for 30GTN,R and R-134a for30GUN,R (see Physical Data tables supplied in the chiller’sinstallation instructions) and should be under sufficient pres-sure to conduct a leak test. If there is no pressure in the system,introduce enough nitrogen to search for the leak. Repair theleak using good refrigeration practices. After leaks arerepaired, system must be evacuated and dehydrated.REFRIGERANT CHARGE (Refer to Physical Data tablessupplied in the chiller’s installation instructions) — Immedi-ately ahead of filter drier in each circuit is a factory-installedliquid line service valve. Each valve has a 1/4-in. Schrader con-nection for charging liquid refrigerant.Charging with Unit Off and Evacuated — Close liquid lineservice valve before charging. Weigh in charge shown on unitnameplate (also in Physical Data tables supplied in the chiller’sinstallation instructions). Open liquid line service valve; startunit and allow it to run several minutes fully loaded. Check fora clear sight glass. Be sure clear condition is liquid and notvapor.Charging with Unit Running — If charge is to be added whileunit is operating, all condenser fans and compressors must beoperating. It may be necessary to block condenser coils at lowambient temperatures to raise condensing pressure to approxi-mately 280 psig (1931 kPa) to turn all condenser fans on. Donot totally block a coil to do this. Partially block all coils in uni-form pattern. Charge each circuit until sight glass shows clearliquid, then weigh in amount over a clear sight glass as listedin Physical data tables supplied in chiller’s installationinstructions.FIELD WIRINGField wiring is shown in Fig. 36-41.UNIT SIZE30GTN,RAND 30GUN,RNOMINALFLOW RATE*MINIMUMFLOW RATE(See Notes)Gpm L/s Gpm L/s040 86 5.43 36.8 2.32045 101 6.37 37.7 2.38050 123 7.76 37.7 2.38060 151 9.53 47.5 3.00070 173 10.91 47.5 3.00080,230B 192 12.11 66.7 4.20090,245B 216 13.62 59.5 3.75100,255B,270B 240 15.14 84.1 5.30110,290B,315B 264 16.65 84.1 5.30130 300 18.9 110 6.9150,230A-255A 348 21.9 110 6.9170,270A,330A/B,360B (50 Hz) 384 24.2 120 7.5190,290A,360A/B (60 Hz),360A (50 Hz), 390B 432 27.2 120 7.5210,315A,390A,420A/B 480 30.2 148 9.3ARI — Air Conditioning and Refrigeration InstituteGpm — Gallons per minute (U.S.)L/s — Liters per secondN — Liters per kWV — Gallons per tonAPPLICATION V NNormal Air Conditioning 3 3.25Process Type Cooling 6 to 10 6.5 to 10.8Low Ambient Unit Operation 6 to 10 6.5 to 10.8IMPORTANT: When adjusting refrigerant charge, circu-late fluid through cooler continuously to prevent freez-ing and possible damage to the cooler. Do notovercharge, and never charge liquid into low-pressureside of system.