Carrier 50XP manual Controls, Operating sequence

CONTROLS

Operating sequence

Cooling — When the system thermostat calls for cooling, 24 V is supplied to the “Y” and “G” terminals of the thermostat. This completes the circuit to the contactor coil (C) and indoor fan board. The normally open contacts of C close and complete the circuit to compressor motor (COMP) and to outdoor (condenser) fan motor (OFM). Both motors start instantly. The IFM starts according to the selection pin set-up on the Easy Select Board.

On the loss of the thermostat call for cooling, 24 V is removed from both the “Y” and “G” terminals (provided the fan switch is in the “AUTO” position) de-energizing the compressor contactor and opening the contacts supplying power to compressor/OFM. After a preselected delay, the IFM shuts off. If the thermostat fan selector switch is in the “ON” position, the IFM will run continuously at speed selected on Easy Select Board

50XP

Heating — If accessory electric heaters are installed, on a call for heat, circuit R-W is made through the thermostat contacts. Circuit R-G is made which energizes the IFM. If the heaters are staged, then the thermostat closes a second set of contacts (W2) when second stage is required. When thermostat is satisfied, contacts open, deenergizing the heater relay. After a preselected delay, the IFM shuts off. If the thermostat fan selector switch is in the “ON” position, the IFM will run continuously at speed selected on Easy Select Board.

NOTE: On units with a Time Guard® II device: Once the compressor has started and then stopped, it cannot be restarted again until 5 minutes have elapsed.

The indoor blower operation with a call for fan operation (G) in cooling mode will perform by the on/off delay profile selected at start up on the Easy Select Board.

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