689103-BIM-B-1012
8
Johnson Controls Unitary Products
COOLING OPERATION
During cooling operation, the control will receive thermostat signals at
the Y and O input terminals. The control will energize the M compressor
output terminal. This signal energizes the coil of the compressor con-
tactor causing the compressor to run. The control also delivers power to
the COND FAN terminals causing the outdoor fan to operate. The con-
trol energizes the REV VALVE terminal with 24VAC to switch the
reversing valve.
HEATING OPERATION
During normal heating mode, the control will receive a thermostat signal
at the Y input terminal. The control will energize the M compressor out-
put terminal. This signal energizes the coil of the compressor contactor
causing the compressor to run. The control also delivers power to the
COND FAN terminals causing the outdoor fan to operate. The reversing
valve is not energized in heating mode.
EMERGENCY HEAT
When the thermostat calls for emergency heat operation (W signal with-
out a Y signal), the control will de-energize the compressor and ener-
gize the W1/66 terminal immediately.
PRESSURE SWITCH FAULT & LOCKOUT
The heat pump is equipped with a pressure switch and an optional low
pressure switch that are connected to the control at the pressure switch
terminals. If the pressure switch input opens for more than 40 millisec-
onds, the control will de-energize the compressor. If the pressure switch
closes and a thermostat call for compressor operation is present, the
control will apply the five-minute anti-short cycle delay timer and start
the compressor when the timer expires.
When the compressor is started following a pressure switch fault, the
control will start a six-hour timer based on accumulated compressor run
time. If the control senses another opening of the pressure switch
before the timer expires, it will cause a soft lockout condition. The sec-
ond opening of the pressure switch must be greater than 160 millisec-
onds for the lockout to occur. If the second opening is between 40 and
160 milliseconds, the control will de-energize the compressor but not
cause a soft lockout condition. If the control does not sense a second
pressure switch opening before the six-hour timer expires, the timer and
counter will be reset.
During the soft lockout mode, the control will de-energize the compres-
sor and energize the X/L output with the appropriate flash code.
The control will reset the soft lockout condition when any of the follow-
ing occur following removal of the fault condition.
1. Power is cycled to the R or Y inputs of the control. This will cause
the soft lockout condition to be reset when the thermostat is satis-
fied or when the thermostat is set to SYSTEM OFF and back to
HEAT or COOL mode.
2. The TEST terminals are shorted for more than two seconds.
When the soft lockout condition is reset, the control will stop displaying
the fault code and will respond to thermostat inputs normally.
FIGURE 10:
Defrost Operation Curves
REGION C
TERMINATE CURVE
INHIBIT CURVE
INITIA
TE
CUR
VE
REGION A
REGION B
REGION D
REGION E
AMBIENT TEMPERATURE
LIQUID
LINE
(COIL)
TEMPERA
TURE
Defrost prevented from starting
No call for defrost
Time Defrost (6 hour) prevented
No call for Defrost
Time Defrost (6 hour) allowed
Call for Defrost
Defrost Terminated
