Controls - Carrier Performance 50VT Product Data

CONTROLS

Operating sequence
When power is supplied to unit, the transformer (TRAN) is
energized.
On units with crankcase heater, heater is also energized.
Cooling — With the thermostat in the cooling position, the
thermostat makes circuit R- -O. This energizes the reversing valve
solenoid (RVS) and places the unit
cooling.
As the space temperature rises, the thermostat closes circuit R- -Y.
A circuit is made to contactor (C), starting the compressor (COMP)
and outdoor- -fan motor (OFM). Circuit R- -G is made at the same
time and starts the indoor- -fan motor (IFM).
When the thermostat is satisfied, contacts open, deenergizing C.
The COMP and OFM stop, and the IFM stops after the preselected
time delay.
Heating — On a call for heat, thermostat makes circuites R- -Y and
R- -G.
A circuit is made to C, starting COMP and OFM. Circuit R- -G also
is complted, energizing IFR and starting IFM after the selected time
delay.
Should room temperature continue to fall, circuit R- -W is made
through second- -stage thermostat. If optional electric heat package
is used, a relay is energized, bringing on first bank of supplemental
electric heat. When thermostat is satisfied, contacts open,
deenergizing contactor and relay; motors and heaters deenergize.
in standby condition for
Defrost — Defrost board (DB) is a time and temperature control,
which includes a field- -selectable time period (dip switch 1 and 2
on the board) between checks for defrost (30, 60, 90, or 120
minutes). Electronic timer and defrost cycle start only when
contactor is energized and defrost thermostat (DFT) is closed.
The defrost board is also equipped with a third dip switch for
selecting Quiet Shift operation. The Quiet Shift operation turns
compressor off at defrost initiation and termination. Unit is factory
shipped with quiet shift turned off.
Defrost mode is identical to cooling mode, except outdoor fan
motor stops and a bank of optional electric heat turns on to warm
air supplying the conditioned space.
NOTE:
1. Compressor time delay occurs through the defrost control
board.
2. Defrost control board has built in 5 minute compressor
delay; once the compressor has started and then stopped, it
cannot be restarted again until 5 minutes have elapsed.
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