Installation guide
Figure13 J Defrost Thermostat
TUBE STUIBcoIL
DEFROST
THERMOSTAT
B. DEFROST CONTROL BOARD
The defrost board is a time/temperature control which in-
cludes a field-selectable time period between defrost
cycles of 30, 60, or 90 minutes (quick-connects located
at board edge, factory set at 90 minutes).
Defrost mode is identical to cooling mode except that out-
door-fan motor stops and second-stage heat is turned
on to continue warming conditioned space.
Initially, the defrost cycle timer starts when the contactor
is energized and a 24 VAC signal is present on the T1 ter-
minal. Then the defrost cycle begins when the defrost
thermostat is closed and the cycle timer times out (30, 60,
90 or minutes).
To initiate a forced defrost cycle, the defrost thermostat
must be closed. This can be accomplished as follows:
1. Turn off power to outdoor unit.
2. Disconnect outdoor fan-motor lead from OF2 on
control board (refer to Figure 14). Tape lead to pre-
vent grounding.
3. Restart unit in heating mode, allowing frost to ac-
cumulate on outdoor coil.
4. After a few minutes in heating mode, liquid line
temperature should drop below closing point of de-
frost thermostat (approximately 32 ° F).
5. Short between speed-up terminals with a flat-
bladed screwdriver (refer to Figure 14). This
reduces the timing sequence to 7, 14, or 21 sec-
onds (30, 60, or 90 minute defrost selection,
respectively).
6. When you hear reversing valve change position,
remove screwdriver immediately; otherwise, con-
trol will terminate normal 10-minute defrost cycle
in approximately 2 seconds.
START-UP PROCEDURE
NOTE: Length of defrost cycle is dependent upon length
of time it takes to remove screwdriver from test pins after
reversing valve has shifted.
7. Unit will remain in defrost for remainder of defrost-
cycle time or until defrost thermostat reopens at
approximately 65 °F coil temperature of liquid line.
8. Turn off power to outdoor unit and reconnect fan-
motor lead to OF2 on control board (refer to Figure
14),
Figure 14 J Defrost Control Board
c_us ol _ _ _:
8
T1 C C O 1 Ip1 J1
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1. Set indoor thermostat selector switch to OFF.
2. Turn ON all electrical disconnect devices.
3. tf unit has a crankcase heater, energize the heater
and wait 24 hours before proceeding.
4. Set indoor thermostat at desired temperature. Be
sure setpoint is below indoor ambient temperature
to call for cooling, or above indoor ambient to call
for heating.
5. Set indoor thermostat selector switch to COOL or
HEAT. Operate unit for minimum 10 minutes, then
check the system refrigerant charge.
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