Bryant 575C, 575B, 541A dimensions Sequence of Operation

LIQUID TEMPERATURE AT LIQUID VALVE (C)

60

54

49

43

38

32

27

21

16

10

Fig. 19A — 575B072 Charging Chart

	140
(F)	130
	ADD CHARGE IF ABOVE CURVE
VALVE
	120
AT LIQUID	110
	100
TEMPERATURE
	90
	80
LIQUID	70
	REDUCE CHARGE IF BELOW CURVE
	60
	50

50	100	150	200	250	300	350	400
		LIQUID PRESSURE AT LIQUID VALVE (PSIG)
344	689	1034	1379	1724	2069	2414
		LIQUID PRESSURE AT LIQUID VALVE (Kilopascals)

Fig. 19B — 575C090,120 Charging Chart

Fig. 19C — 541A180 Charging Chart

SEQUENCE OF OPERATION

I. 575B072 UNITS

When power is supplied to unit, the transformer (TRAN) and crankcase heater (CCH) are energized.

A. Cooling

On a call for cooling, the thermostat completes the following circuits: R-G, R-Y, and R-O. If the compressor recycle delay of 3 minutes is complete, the compressor and outdoor fan start. The reversing valve is energized for cooling and the indoor- fan motor starts.

When the thermostat is satisfied, the circuits are opened, and the compressor, outdoor-fan motor, and indoor-fan motor stop. The reversing valve is deenergized.

B. Heating

On a call for heating, the thermostat completes the following circuits: R-G and R-Y. If the compressor recycle delay of 3 minutes is complete, the compressor and outdoor fan start. The indoor-fan motor will also start.

If room temperature continues to fall, the thermostat completes circuit R-W. If the optional electric heat package is used, the heat relay is energized, and the electric heaters are energized.

When the thermostat is satisfied, the circuits are opened, and the compressor, outdoor-fan motor, heaters, and indoor- fan motor stop.

C. Defrost

Defrost board (DB) is a time and temperature control, which includes a field-selectable time period between checks for frost (30, 50, and 90 minutes). Electronic timer and defrost cycle start only when contactor is energized and defrost ther- mostat (DFT) is closed (below 28 F).

Defrost mode is identical to Cooling mode, except outdoor-fan motor (OFM) stops and a bank of supplemental electric heat turns on to warm air supplying the conditioned space. Defrost mode is terminated when the DFT reaches 65 F.

D. Air Circulation

When the fan switch is at FAN ON, the indoor-air fans oper- ate continuously to provide ventilation. The thermostat operates the other components as described above.

E. Emergency Heat Cycle

If the compressor is inoperative due to a tripped safety device, the second stage of the thermostat automatically energizes the indoor-air fan and the electric resistance heat- ers (if equipped).

II. 575C090,120 UNITS

When power is supplied to unit, the transformer (TRAN) is energized. The crankcase heater is also energized.

A. Cooling

With the thermostat subbase in the cooling position, and when the space temperature comes within 2° F of the cooling set point, 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 continues to rise, the second stage of the thermostat makes, closing circuit R-Y. When compres- sor time delay (5 ± 2 minutes) is completed, 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 contactor (IFC) and starting the indoor-fan motor (IFM) after one-second delay.

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