035-17421-000 Rev B (700)
Unitary Products Group
11
option out-door thermostat can be used to turn on only the
first stage of electric heat if the temperature is above the set-
ting tempera-ture. If gas/propane furnace is used as the sup-
plemental heat, add-on control kit (2AC02700701) must be
used. See the add-on control installation instruction for the
system operation.
EMERGENCY HEAT:
When switch on thermostat is placed in emergency heat posi-
tion:
1.
Emergency light is energized.
2.
Compressor circuit is locked out. (No "R" to "Y")
3.
Supplemental and standby heaters (if installed) will be
controlled by first stage of heating thermostat.
4.
Indoor blower will operate on demand for heat and cycle
off with the last heater element when in “AUTO” position.
SAFETY LOCKOUT MODE:
The lock out control opens the circuits to the compressor con-
tactor, stopping the compressor in respond to 400 +/-10 PSIG
high pressure limit switch opening for more than 40 millisec-
onds. The compressor will remain off until the high pressure
switch recloses and a 5 minutes antishort cycle timer has
expired. When the compressor re-starts, a six hour timer shall
be initialized to accumulate the compressor run time. If the hi
pressure switch opens during his six hour run time, the com-
pressor will be locked-out. If the high pressure switch does
not open during this run time, the unit continues with normal
operation. During locked-out, the defrost relay and the com-
pressor contactor remain de-energized.
If the control detects a high pressure switch opening then it
will send an output to turn on a fault indicator light at the ther-
mostart through X/L terminal. Code flashed will be either 2
flashes if the pressure switch opens during cooling or heating
mode or 3 flashes if the pressure switch opens during the
defrost mode.
To reset the lock out mode:
1) Remove the 24V power from the Y or/and R for more than
2 second (turn off the system from the thermostart or power
to the indoor air handler)
2) Connect a 1000 Ohm or smaller jumper across the "test"
terminals for more than 2 seconds
The control has the capability to sense a low voltage condi-
tion. If the voltage drops below 18 VAC, the control will not
energize the compressor relay. If the unit is running when the
voltage drops, the contactor will remain closed until it drops
below 16 VAC. The antishort cycle timer will be initiated and
the control will not bring the compressor back until the anti-
short cycle period is complete and the voltage is above
18VAC.
DEFROST CYCLE:
The defrost control is a time/temp control which includes a
field-selectable time period between defrost cycle (30, 60, or
90 minutes). Factory set at 60 minutes. See figure 10.
The electronic timer will accumulate the compressor run time.
At the end of the setting cycle time(30. 60, or 90 minutes), the
control will check the defrost thermostat status. If the defrost
thermostat is closed, the defrost cycle will be initiated. The
defrost thermostat is closed when the liquid temperature falls
FIGURE 9 : HEAT PUMP FLOW DIAGRAM
FLOW
RATER
(cooling)
INDOOR COIL
COMPRESSOR
4-WAY
REVERSING
VALVE*
SUCTION
ACCUMULATOR
OUTDOOR
COIL
COOLING CYCLE FLOW
HEATING CYCLE FLOW
* SHOWN IN COOLING POSITION
FIELD CONNECTED LINE
FIELD CONNECTED LINE
LIQUID
SENSOR
FLOW RATER (heating)
FILTERDRYER
(solidcore).
