Daikin DAR09 - Page 46

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SYSTEM OPERATION
DEFROST CYCLE - LEGACY MODELS
The defrosng of the outdoor coil is jointly controlled by the
defrost control board and the defrost thermostat.
Solid State Defrost Control
During operaon 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 ming periods of 30, 60, or 90 minutes may be selected
by connecng the circuit board jumper to 30, 60, or 90 respec-
vely. Accumulaon of me for the ming period selected starts
when the sensor closes (approximately 31° F), and when the
room thermostat calls for heat. At the end of the ming period,
the unit’s defrost cycle will be iniated provided the sensor re-
mains closed. When the sensor opens (approximately 75° F), the
defrost cycle is terminated and the ming 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-
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 posion, the “O”
terminal on the thermostat is energized all the me.
Care must be taken when selecng a room thermostat. Refer
to the installaon instrucons 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
ows through the magnec holding coils of the compressor
contactor (CC) and fan relay (RFC).
This draws in the normally open contact CC, starng the com-
pressor condenser fan motors. At the same me, contacts RFC
close, starng the indoor fan motor.
When the thermostat is sased, it opens its contacts, breaking
the low voltage circuit, causing the compressor contactor and
indoor fan relay to open, shung down the system.
If the room thermostat fan selector switch should be set to the
“on” posion, then the indoor blower would run connuously
rather than cycling with the compressor.