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Unitary Products Group
below approximately 31F. If the room thermostat opens dur-
ing defrost, the control will resume operation in defrost when
the thermostat re-closes.
The defrost mode is identical to the cooling mode except that
the outdoor fan motor stops and the first stage of heat (5KW if
electric heat) is turned on through w1/66 to continue warming
the conditioned space. The defrost cycle will be terminated
when the defrost thermostat is opened at 55F or 10 minutes
of compressor accumulated run time, whichever comes first.
Note: the delay in the response of defrost thermostat may
allow the coil temperature to reach 75-80F. The 10 minute
timer will stop if the "Y" signal is dropped during defrost.
TEST PIN:
The "test" terminals are designed for two uses:
1.
Anti-Short Cycle By-Pass — To by-pass the anti-short
cycle feature in the control, jumper the two "test" termi-
nals for at least 2 seconds. If there is a "Y" signal to the
control, jumpering the test terminal will allow the control
to pull in the unit contactor immediately. Note: do not
hold the jumper on the test terminal for more than 9 sec-
onds as the control will go into the defrost mode.
2.
Forced Defrost — To force the unit into the defrost mode
(24V to reversing valve and no fan operation) while the
unit is operating, jumper the test terminals for 2 seconds
if the unit was running (If the unit was not running and
step 1 above was used to start the unit, then the "test"
terminals must be held for at least 10 seconds). When
the short is removed, the heat pump will remain in
defrost until the defrost thermostat opens or 10 minutes
expires. If the thermostat is open when the short is
removed, the heat pump will exit defrost immediately.
INSTRUCTING THE OWNER
Assist owner with processing warranty cards. Review User’s
Information Manual and provide a copy for the owner guid-
ance on proper operation and maintenance. Instruct the
owner or the operator how to start, stop and adjust tempera-
ture setting. The owner should also be instructed about the 5
minute off cycletimer and the defrost operation.
When applicable, instruct the owner that the compressor is
equipped with a crankcase heater to prevent the migration of
refrigerant to the compressor during the “OFF” cycle. The
heater is energized only when the unit is not running. If the
main switch is disconnected for long periods of shut down, do
not attempt to start the unit for 8 hours after the switch has
been connected. This will allow sufficient time for all liquid
refrigerant to be driven out of the compressor. The installer
should also instruct the owner on proper operation and main-
tenance of all other system components.
INDICATIONS OF PROPER OPERATION
COOLING
Cooling operation is the same as any conventional air condi-
FIGURE 10 : TIME / TEMPERATURE DEFROST BOARD
REV
TEST
RUN TIME
RUN TIME
30
90
60
PRESSURE
DEST
M
K2
R3
K1
R7
K3
M
T’STAT
SWITCH
VALVE
6TT-3
PN
031-09104-000
Time Selection
Tap
Reversing
Valve
Pressure
Switch
Defrost
Thermostat
Test Pin
Contactor
Coil
W1/66
W
Y
O
C
R
X/L
