NOTE: Use only Carrier approved compressor oil. Ap-
proved sources are: Petroleum Specialties Inc. (Cryol 150A), Texaco, Inc. (Capella WF-32-150), and Witco Chemical Co. (Suniso 3GS). Do not reuse oil that has been drained out, or oil that has been exposed to atmosphere.
REMOVE OIL Ð Pump down compressor to 2 psig (14 kPag). Loosen the 1¤4-in. (6.4-mm) pipe plug at the com- pressor base and allow the oil to seep out past the threads of the plug.
NOTE: The crankcase will be slightly pressurized. Do not remove the plug, or the entire oil charge will be lost.
Small amounts of oil can be removed through the oil pump discharge connection while the compressor is running.
Preliminary Charge Ð Refer to GTAC II (General Train- ing Air Conditioning), Module 5, Charging, Recovery, Recycling, and Reclamation for charging procedures. Using the liquid charging method and charging by weight proce- dure, charge each circuit with the amount of R-22 listed in Table 3A, 3B, 4A, or 4B.
Never charge liquid into the low-pressure side of sys- tem. Do not overcharge. During charging or removal of refrigerant, be sure indoor-fan system is operating.
Start Unit Ð The ®eld disconnect is closed, the fan cir- cuit breaker is closed, and the space thermostats are set above ambient so that there is no demand for cooling. Only the crankcase heaters are energized.
Close the compressor circuit breakers and then reset both space thermostats below ambient so that a call for stage one cooling is ensured. Lead refrigeration circuit ther- mostat TC1 must be set to call for cooling at a lower tem- perature than lag refrigeration circuit thermostat TC2. See Table 16 for lead/lag circuits on all units. Now set TC2 for cooling.
NOTE: Do not use circuit breakers to start and stop the com- pressor except in an emergency.
38AH044-084 DUAL-CIRCUIT UNITS Ð Start-up of lead compressor A1 (Table 16) will be delayed from 12 seconds to 51¤2 minutes from the time the call for cooling is initiated by TC1. After the lead compressor starts, close the TC2 ther- mostat to start lag circuit compressor B1. Compressor B1 will start a minimum of 60 seconds after thermostat TC2 is closed.
38AH044-084 OPTIONAL SINGLE CIRCUIT UNITS Ð Start-up of lead compressor A1 (Table 16) is delayed from 12 seconds to 51¤2 minutes from the time the call for cooling is initiated by TC1. Closure of TC2 will actuate LLS-A2. Lag compressor A2 is controlled by D-D2 timer contacts and capacity control pressure switches (CCPSs) which monitor compressor suction pressure. The lag compressor starts ap- proximately 21¤2 minutes after the lead compressor starts if the suction pressure is above the CCPS set point.
38AH094,104 UNITS Ð Start-up of lead circuit A, compressor A1 (Table 16) is delayed from 12 seconds to 51¤2 minutes from the time the call for cooling is initiated. After lead circuit A, compressor A1 starts, close refrig- eration circuit thermostat TC2 to start lag circuit B, lead
compressor B1. Start-up of compressor B1 is delayed from 12 seconds to 51¤2 minutes. (Circuit B of unit 38AH094 has only one compressor.)
Each circuit's lead compressor start-up is controlled by the unit control timer. The circuit's lag compressor start-up is controlled by the D-D2 timer contacts and capacity control pressure switches (CCPSs) which monitor compres- sor suction pressure. The circuit's lag compressor will start approximately 21¤2 minutes after a call for cooling if com- pressor pressure is above CCPS set point.
38AH124,134 UNITS Ð Start-up of the lead circuit (Module 124A or 134A) lead compressor A1 (Table 16) is delayed from 12 seconds to 51¤2 minutes from the time the call for cooling is initiated by TC1. Lag compressor A2 is controlled by D-D2 timer contacts and capacity control pres- sure switches (CCPSs) which monitor compressor suction pressure. The lag compressor starts approximately 21¤2 min- utes after the lead compressor starts if the suction pressure is above the CCPS set point.
After the lead circuit (Module 124A or 134A) lead com- pressor A1 (Table 16) starts, close the TC2 thermostat to start the lag circuit (Module 124B or 134B) lead compressor (A1). Lag circuit compressor A1 start-up is delayed from 12 sec- onds to 51¤2 minutes from the time the call for cooling is initiated by TC2. Lag compressor A2 is controlled by D-D2 timer contacts and CCPSs which monitor compressor suc- tion pressure. Lag compressor A2 starts approximately 21¤2 minutes after lead compressor A1 starts if the suction pres- sure is above the CCPS set point.
Adjust Refrigerant Charge
Never charge liquid into the low-pressure side of sys- tem. Do not overcharge. During charging or removal of refrigerant, be sure indoor-fan system is operating.
With all fans operating, and all compressors on the cir- cuit being serviced operating at full capacity, adjust the refrigerant charge in accordance with the unit charging charts located on the inside of the control box doors and in Fig. 30-43. Charge vapor into compressor low-side service port located above oil pump crankshaft housing. Measure pressure at the liquid line service valve, making sure a Schrader depressor is used if required. Also, measure liquid line tem- perature as close to the liquid service valve as possible. Add charge until the pressure and temperature conditions of the charging chart curve are met. If liquid pressure and tempera- ture point fall above curve, add charge. If liquid pressure and temperature point fall below curve, reduce the charge until the conditions match the curve.
If the sight glass at location A (Fig. 11 and 12) is cloudy, check refrigerant charge again. Ensure all fans and com- pressors on the circuit being serviced are operating. Also ensure maximum allowable liquid lift has not been exceeded.
If the sight glass at location A is clear and the sight glass at location B is cloudy, a restriction exists in the line between the 2 sight glasses. Check for a plugged ®lter drier or partially open solenoid valve. Replace or repair, as needed.
