Carrier 50SZ Series, Данные о продукции

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27
CONTROLS
Sequence of operation
When power is supplied to unit, the transformer (TRAN) is ener-
gized.
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 in-
door--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 30 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 RG 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 sup-
plemental 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
30 seconds.
Defrost
⎯
Defrost board (DB) is a time and temperature control,
which includes a field--selectable time period between checks for
defrost (30, 60, 90, and 120 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 mo-
tor 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 re-
started again until 5 minutes have elapsed.
50SZ