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SERVICE
WARNING
!
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury
or death.
Before installing, modifying, or servicing system, main
electrical disconnect switch must be in the OFF position.
There may be more than 1 disconnect switch. Lock out and
tag switch with a suitable warning label.
High−Pressure Relief Valve
The high−pressure relief valve is located in the compressor. The
relief valve opens at a pressure differential of approximately 550 to
625 50 psig between suction (low side) and discharge (high side)
to allow pressure equalization.
Internal Current and Temperature Sensitive Overload
The control resets automatically when internal compressor motor
temperature drops to a safe level (overloads may require up to 45
minutes to reset). When an internal overload is suspected of being
open, check by using an ohmmeter or continuity tester.
Pumpdown Procedure
The system may be pumped down in order to make repairs on the
low side without losing complete refrigerant charge.
CAUTION
!
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment
damage or improper operation.
Never open system to atmosphere while it is under a vacuum.
When system must be opened for service, recover refrigerant, break
vacuum with dry nitrogen before opening system.
1. Attach pressure gage to suction service valve gage port.
2. Front−seat the liquid/mixed phase line valve.
CAUTION
!
UNIT DAMAGE HAZARD
Failure to follow this caution may result in equipment
damage or improper operation.
The unit coils hold only the factorydesignated amount of
refrigerant. Additional refrigerant may cause units to relieve
pressure through the compressor internal pressure relief
valve (indicated by a sudden rise of suction pressure) before
suction pressure reaches 20 psig. If this occurs, shut off unit
immediately then front−seat the suction valve and remove
and recover excess refrigerant following accepted practices
3. Start unit and run until suction pressure reaches 20 psig.
4. Shut unit off and front−seat suction valve.
5. De−pressurize low side of unit and recover refrigerant fol-
lowing accepted practices.
High−Pressure Switch
The high−pressure switch, located on discharge line, protects
against high discharge pressures caused by such events as
overcharge, condenser−fan motor failure, system restriction, etc. It
opens on pressure rise at about 670 10 psig. If system pressures
go above this setting during abnormal conditions, the switch
opens.
428 01 9702 01
PERSONAL INJURY HAZARD
Failure to follow this warning could result in personal
injury or death.
DO
abnormalities − high pressures pose a serious safety
hazard.
The high−pressure switch is checked with an ohmmeter. If system
pressure is below 470 psig switch shows continuity.
Crankcase Heater
The crankcase heater prevents refrigerant migration and
compressor oil dilution during shutdown when compressor is not
operating. If the crankcase heater is de−energized for more than 6
hours, both compressor service valves must be closed.
The crankcase heater is powered by the high−voltage power of the
unit. It is connected across the line side of the contactor and is
thermostatically controlled.
PERSONAL INJURY HAZARD
Failure to follow this warning could result in personal injury
or death.
Use extreme caution when troubleshooting this device as
line voltage is continually present.
To troubleshoot:
1. Apply voltmeter across crankcase heater leads to see if heat-
2. With power off and heater leads disconnected, check across
Service Valves
The service valves in the outdoor unit come from the factory
front−seated. This means the refrigerant charge is isolated from the
line−set connection ports. To prevent damage to the valve, use a
wet cloth or other accepted heat sink material on the valve before
brazing.
The service valve cannot be field repaired, therefore, only a
complete valve or valve stem seal and service port caps are
available for replacement.
Defrost Controls
The control, which consists of defrost control board and defrost
thermostat, interrupts the normal system heating operation to
defrost the outdoor coil, if the coil saturated suction temperature
indicates freezing temperatures. Defrost control board can be field
set to check need for defrost every 30, 50, or 90 minutes of
operating time, by connecting the jumper (labeled W1, on the
circuit board) to the spade terminal for the defrost time desired. The
board is factory set for 60 minutes. The defrost period is field
selectable, depending upon geographic areas and defrost demands.
Control board has additional feature that allows unit to restart in
defrost cycle if room thermostat is satisfied during defrost. Defrost
control simultaneously tops outdoor fan, energizes reversing valve
solenoid to return system to cooling cycle (outdoor unit as
condenser, indoor unit as evaporator), and activates accessory
electric heater.
Specifications subject to change without notice.
WARNING
!
NOT
attempt
to
simulate
WARNING
!
er voltage is on. Do not touch heater. Carefully feel area
around crankcase heater; if warm, crankcase heater is func-
tioning.
leads with ohmmeter. Do not look for a specific resistance
reading. Check for resistance or an open circuit, and change
heater if an open circuit is detected.
these
system
5
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