035-18550-001-A-0902
20
Unitary Products Group
8.
Supplemental electric heat (if installed) will be con-
trolled by second stage TH2 of the thermostat. The
supplemental electric heat circuit is controlled
through low voltage terminals W, 60 and 66. The
standby portion of electric heat (controlled through
low voltage terminal 53) cannot operate because
relay RY1 is energized, opening the circuit to termi-
nal 53, whenever the compressor is operating.
9.
When second stage heating TH2 is satisfied, the
supplemental heaters will be de-energized.
DEFROST CYCLE
When condensate freezes on the outdoor coil during
heating operation, it must be defrosted before it blocks
the flow of air across the coil.
1.
A defrost cycle will be initiated by the defrost con-
trol board's timed defrost feature.
2.
When the defrost cycle is initiated, the unit oper-
ates as follows:
a.
The reversing valve solenoid is energized through
the defrost control board causing the unit to switch
to the cooling cycle.
b.
Defrost control board de-energizes 2M contactor,
causing the outdoor section fan(s) to shut down.
c.
Supplemental electric heat (if installed) will be ener-
gized through defrost control board. Only that por-
tion of electric heat controlled through low voltage
control terminal 66 will be energized by the defrost
cycle. The operation of supplemental electric heat
during unit defrost will prevent cold drafts in the con-
ditioned space.
3.
The defrost cycle will be terminated when:
a. the liquid temperature exceeds 55°F, or
b. 10 minutes have passed since defrost initiation.
The 10 minute cycle time (independent of liquid line
temperature) is controlled by the defrost control board.
4.
At defrost termination, the unit returns to the nor-
mal heating operation.
OPERATION BELOW 0°F OUTDOOR TEMPERATURE
1.
At 0°F outdoor temperature, the low temperature
compressor cutoff thermostat 1TH contacts 1 and 3
will open, de-energizing contactor 1M which shuts
down the compressor. Contacts 1 and 2 of thermo-
stat 1TH are closed when contacts 1 and 3 are
open. This feature allows the standby electric heat
(if installed) to operate under control of first stage
heating TH1 of the room thermostat whenever the
compressor is shut-down by the 1TH control. The
supplemental electric heat will continue to be con-
trolled by the second stage TH2 of the room ther-
mostat same as described under Item 8 of
HEATING OPERATION.
2.
The indoor section blower operation will be con-
trolled by the first stage heating TH1 of the room
thermostat if the fan switch is in the “AUTO” posi-
tion.
EMERGENCY HEAT OPERATION
When the system switch on the room thermostat is
placed in the EMERGENCY HEAT position, operation
is as follows:
1.
The emergency heat light on the room thermostat
will be energized.
2.
Compressor will not operate because the Y circuit
of the room thermostat cannot be energized.
3.
Supplemental and standby electric heat (if
installed) will be controlled by first stage heating
TH1 of room thermostat.
4.
Indoor section blower will also be controlled by first
stage heating TH1 if fan switch is in the “AUTO”
position.
SAFETY FEATURES
1.
All condenser fan motors have inherent protection
with automatic reset.
2.
Every compressor is internally protected against
over current, excessive temperature and primary
single phasing.
This protection is provided by a line break motor
protector that is mounted inside the compressor
housing and is connected between each winding
and the common terminal.
3.
Every compressor is protected by crankcase heat-
ers to prevent refrigerant from accumulating in the
crankcases of the compressor during an “OFF”
cycle.
4.
All condenser fan motors and the secondary of
every transformer is grounded.
