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SYSTEM OPERATION
DEFROST CYCLE - LEGACY MODELS
The defrosting of the outdoor coil is jointly controlled by the
defrost control board and the defrost thermostat.
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 respec
-
tively. 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 re
-
mains 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 interrupts the unit’s defrost period. The
new upgraded defrost control has a 12 minute override inter
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rupt.
HEATING CYCLE
The reversing valve on the DZ11S, DZ13S, DZ14S, DZ16S, DS16
and DZ18 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.
HEATING CYCLE - LEGACY ROOM THERMOSTATS
When the room thermostat calls for heat, the contacts of the
room thermostat close making terminals R to Y & G, the low
voltage circuit of the transformer is completed. Current now
flows through the magnetic holding coils of the compressor
contactor (CC) and fan relay (RFC).
This draws in the normally open contact CC, starting the com
-
pressor condenser fan motors. At the same time, contacts RFC
close, starting the indoor fan motor.
When the thermostat is satisfied, it opens its contacts, breaking
the low voltage circuit, causing the compressor contactor and
indoor fan relay to open, shutting down the system.
If the room thermostat fan selector switch should be set to the
“on” position, then the indoor blower would run continuously
rather than cycling with the compressor.
Summary of Contents for DAR09
Page 59: ...59 SERVICING Table 1 Quick Reference Table...
Page 81: ...81 AIRHANDLERS...
Page 96: ...96 REM OTE SPLITS...