Carrier 38AH044-084 specifications Timer Cycle

38AH044-084 DUAL-CIRCUIT UNITS; 38AH094,104 Ð If circuit A operation is insufficient for the cooling require- ments, the thermostat second stage TC2 closes to bring cir- cuit B on-line for cooling. This circuit follows the same se- quence of operation as the lead circuit, except a 60-second time delay relay (TDR) delays compressor start-up for 60 seconds after the call for cooling.

38AH044-084 OPTIONAL SINGLE-CIRCUIT UNITS: MOD- ULES 124A, 124B, 134A, AND 134B

NOTE: This sequence of operation assumes that 2 thermo- stats control units 38AH124 or 134 with one thermostat con- trolling each module.

If compressor A1 is insufficient for the cooling require- ments, the thermostat second stage closes, which opens the liquid line solenoid valve LLS-A2. Compressor A2 starts only after D-D2 contacts in the timer close and the suction pres- sure is sufficient to close the capacity control switches.

ALL UNITS Ð When the fan switch is set for automatic (AUTO) operation, the indoor-fan contactor (IFC) is cycled with the lead compressor. If the fan switch is set for con- tinuous (CONT), the IFC is energized as long as the unit power is on.

Restart After Stoppage by Safety Control Ð The high-pressure switch, compressor discharge gas thermostats, and the oil pressure switch must be reset manually by break- ing the control power supply at any of the following points: control circuit fuse, fan motor circuit breaker, or the ther- mostat. Restart follows the Time Guard control delay.

Stoppage by low-pressure switch results in Time Guard control delay, then unit attempts normal restart.

The compressor motor overcurrent protectors are manual- reset circuit breakers. Reset of control circuit may also be necessary.

Independent Refrigerant Circuit Controls Ð Each refrigeration circuit is controlled by independent circuitry. Therefore, it is possible to maintain partial cooling capabil- ity even if one compressor is inoperable.

NOTE: The 38AH044-084 optional single-circuit units do not have independent control circuitry.

NOTE: Black denotes closed contacts.

Fig. 47 Ð Timer Cycle

Unit Control Box Ð (See Fig. 48.) Viewed facing com- pressors, the control box is at left end of the unit. All in- coming power enters through the control box. The control box contains power components and electronic controls. Outer panels are hinged and latched for easy opening. Remove screws to remove inner panels. Outer panels can be held open for service and inspection by using door retainer on each panel. Remove bottom pin from door retainer assembly, swing re- tainer out horizontally, and engage pin in one of the retainer ears and the hinge assembly.

Condenser Fans Ð Each fan is supported by a formed wire mount bolted to fan deck and covered with a wire guard. The exposed end of fan motor shaft is protected from weather by grease. If fan motor must be removed for service or re- placement, be sure to regrease fan shaft, and reinstall fan guard. For proper performance, fan should be 7¤8 in. (22 mm) below top of venturi on the fan deck to top of the fan hub for 60-Hz units, and 1¤2 in. (13 mm) for 50-Hz units. (See Fig. 49.) Tighten set screws to 15 ± 1 ft-lbs (20 ± 1.3 N-m). Figure 49 shows proper position of mounted fan.

IMPORTANT: Check for proper fan rotation (clock- wise viewed from above). If necessary to reverse, switch leads.

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