CSCF R-22 Service Manual

SYSTEM OPERATION

DEFROST CYCLE

The defrosting of the outdoor coil is jointly controlled by the

defrost timing board, defrost (30/60) control, and compressor

run time.

Solid State Defrost Control

During operation the power to the circuit board is controlled

by a temperature sensor, which is clamped to a return bend

(3/8" coils) or a feeder tube (5 mm coils) entering the outdoor

coil. Defrost timing periods of 30, 60, or 90 minutes may be

selected by connecting the circuit board jumper to 30, 60, or

90 respectively. Accumulation of time for the timing period

selected starts when the sensor closes (approximately 31°

F), and when the room thermostat calls for heat. At the end

of the timing period, the unit’s defrost cycle will be initiated

provided the sensor remains closed. When the sensor opens

(approximately 75° F), the defrost cycle is terminated and the

timing period is reset. If the defrost cycle is not terminated

due to the sensor temperature, a ten minute override inter-

rupts the unit’s defrost period. The new upgraded defrost

control has a 12 minute override interrupt.

W2 DFT

DF1

DF2

HEATING CYCLE

The reversing valve on the heat pump models is energized in

the cooling cycle through the "O" terminal on the room

thermostat.

These models have a 24 volt reversing valve coil. When the

thermostat selector switch is set in the cooling position, the

"O" terminal on the thermostat is energized all the time.

Care must be taken when selecting a room thermostat. Refer

to the installation instructions shipped with the product for

approved thermostats.