COOLING SYSTEM
The cooling section is a complete factory package utilizing an
air-cooled condenser. The system is factory-charged with
Refrigerant-22. The compressors are hermetically sealed and
internally sprung.
The compressors also have inherent (internal) protection. If
there is an abnormal temperature rise in a compressor, the
protector will open to shut down the compressor.
PRELIMINARY OPERATION COOLING: After installation has
been completed, energize the crankcase heaters for at least
four hours before operating unit. After this initial warm-up, the
compressors should be given three false starts (energized just
long enough to make a few revolutions) with 5-7 minutes delay
between each start before being put into full time service.
NOTE: Prior to each cooling season, the crankcase heaters
must be energized at least 10 hours before system is
put into operation.
C OO L I N G S E Q U E N C E O F O P E R AT ION: W h e n t h e
thermostat calls for “first-stage” cooling, the low voltage control
circuit from “R” to “G” and “Y1" (wiring schematic) is completed
to energize compressor #1, outdoor fan motor #1 and blower
motor simultaneously.
When the thermostat calls for “2nd-stage” cooling, the low
voltage control circuit from “R” to “Y2" is completed to energize
compressor #2 and outdoor fan motor #2.
After the thermostat is satisfied and opens, all components
likewise stop simultaneously.
The reversing valve is energized thru the "Y1" circuit when the
subbase is in the cooling mode.
The suction line freezestat will cut the compressor out when
the suction line temperature drops below 26
°
F. This is an
automatic reset device.
GENERAL: With the proper thermostat, continuous blower
operation is possible by closing the R to G circuit. This, of
course, alters the sequences for this component operation.
HEATING SYSTEM (HEAT PUMP)
COOLING MODE: Normal heat pump cooling operation. The
reversing valves, compressors, and outdoor fan motors are
energized through the Y1 and Y2 terminals. The indoor blower
motor is energized by terminal G. Two stages of mechanical
cooling are provided.
HEATING MODE - AMBIENT TEMPERATURE ABOVE
BALANCE POINT: The unit will operate in the mechanical
heating mode with both compressors energized through the
heat relay for stage 1 heating (W1). Terminal W2 will have no
affect on the unit in this situation. The indoor blower motor will
be energized by the blower interlock relay K5 on the relay
board. Gas heat will not be energized unless there is a lockout
condition or until the ambient temperature falls below the
balance point setting. One stage of mechanical heating is
provided.
HEATING MODE - DEFROST: When the unit is operating in
the mechanical heating mode and one compressor goes into a
defrost cycle, the gas heat will not be energized. The gas heat
will be energized only when both systems are in the defrost
mode simultaneously. When one of the defrost cycles
terminates, the gas heat will be shut off.
HEATING MODE - AMBIENT TEMPERATURE BELOW
BALANCE POINT: When the ambient temperature drops
below the balance point setting, the controls will disable the
mechanical heat and enable the gas heat. The gas heat will
cycle on first stage (W1) demand with second stage gas heat
available through terminal (W2). After a time delay, the indoor
blower motor will be energized through the blower interlock
relay K5 on the relay board. Two stages of gas heat are
available.
HEATING MODE - EMERGENCY HEAT AT THE ROOM
THERMOSTAT: If the indoor thermostat is set to Emergency
Heat, the unit controls will disable the mechanical heat and
energize the gas heat anytime there is a call for first stage
heating (W1) independent of the ambient temperature and the
balance point. This Emergency Heat mode is enabled by
energizing terminal E. Second stage gas heat will be energized
by terminal W2.
COMPRESSOR LOCKOUT: Anytime a safety switch opens,
the controls will send a signal through the X terminal on TB1 to
the indoor thermostat to indicate a problem. Only the locked-out
compressor will be disabled in cooling, but both compressors
will be disabled in heating. The gas heat will not be energized
by first stage heat (W1) independent of the ambient
temperature and the balance point. Lockout must be reset by
interrupting power at the disconnect switch.
GENERAL: During the installation process, the installer must
set the balance point thermostat which is located behind the
blower access panel in the blower compartment. The balance
point thermostat should be set 5 degrees higher than the
calculated balance point. When the unit leaves the factory, the
balance point thermostat will be set to 50
°
F (the highest
setting).
OPERATION
511.17-N2W
Unitary Products Group
11
