Daikin ComfortNet DX7TC Service Instructions Manual page 33

SYSTEM OPERATION
When the thermostat is satisfied, appropriate commands are
sent to the UC control. The compressor relay and outdoor
fan relay is de-energized. The compressor high stage solenoid
is de-energized if it was energized. The UC control sends an
appropriate command to the indoor unit to de-energize the
indoor blower motor.
DEFROST CYCLE - COMFORTNET™ MODELS
The defrosting of the outdoor coil is jointly controlled by the UC
PCB and the outdoor coil temperature (OCT) sensor.
The OCT sensor is clamped to a feeder tube entering the outdoor
coil. Defrost timing periods of 30, 60, 90 or 120 minutes may
be selected via the dipswitch settings on the UC PCB. In a
communicating system, the defrost timing periods can also be
selected in the communicating thermostat user menu. During
operation, if the coil temperature is low enough (approximately
31°F), the microprocessor will accumulate the compressor run
time. When the total compressor run time reaches 30, 60, 90
or 120 minutes, and there is a call for heat, the PCB will initiate
a defrost cycle. When the microprocessor detects the coil
temperature to be high enough (approximately 75°F), or 10
minutes of maximum defrost cycle time has elapsed, whichever
occurs first, the defrost cycle is terminated and the timing period
is reset. The field service personnel can also advance a heat
pump to the defrost cycle by simultaneously pressing the "TEST"
button and the "RECALL" button on the UC board.
Use the dipswitches to select defrost time interval (30, 60, 90 or
120 minutes) See chart below
ADDED FROM RS6200007r2 During operation, if the coil
temperature is low enough (approximately 31°F), the
microprocessor will accumulate the compressor run time. When
the total compressor run time reaches 30, 60, 90 or 120 minutes,
and there is a call for heat, the PCB will initiate a defrost cycle.
33