Bryant 601A - Manual (Page 26)

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SEQUENCE OF OPERATION
When power is supplied to unit, the transformer (TRAN) is
energized.
On units with crankcase heater, heater is also energized.
Cooling — With the thermostat subbase in the cooling position,
the thermostat makes circuit R-O. This energizes the reversing
valve solenoid (RVS) and places the unit in standby condition for
cooling.
As the space temperature rises, the thermostat makes, closing
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, energizing the indoor-fan relay (IFR)
and starting the indoor-fan motor (IFM) after a 1-second delay.
When the thermostat is satisfied, contacts open, deenergizing C.
The COMP and OFM stop, and the IFM stops after a 60 second
time delay.
Heating — On a call for heat, thermostat makes circuits R-Y
and R-G.
A circuit is made to C, starting COMP and OFM. Circuit R-G also
is completed, energizing IFR and starting IFM after a 1-second
delay.
Should room temperature continue to fall, circuit R-W is made
through second-stage thermostat bulb. 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. The IFM is controlled by a time-delay relay
that keeps the fan on for 60 seconds.
Defrost — Defrost board (DB) is a time and temperature control,
which includes a field-selectable time period between checks for
defrost (30, 50, and 90 minutes). Electronic timer and defrost
cycle start only when contactor is energized and defrost
thermostat (DFT) is closed.
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.
NOTES:
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.
CONTROLS