Filter Drier — Replace whenever refrigerant system is
exposed to atmosphere.
Protective Devices
COMPRESSOR PROTECTION
Overtemperature — Each compressor has an internal pro-
tector to protect it against excessively high discharge gas
temperatures.
Overcurrent — Each compressor has internal line break mo-
tor protection, except the circuit no. 1 on the 50TJ028 unit.
Compressor no. 1 on the 50TJ028 unit uses an electronic
module located with the compressor junction box, to pro-
vide motor protection. This electronic module monitors wind-
ing and discharge temperatures. If these temperatures reach
the trip values, the module interrupts the control line and
causes the compressor to switch off.
Crankcase Heater — Only the 50TJ028 unit is equipped with
a 70-watt crankcase heater to prevent absorption of liquid
refrigerant by oil in the crankcase when the compressor is
idle. The crankcase heater is energized whenever there is a
main power to the unit and the compressor is not energized.
IMPORTANT: After prolonged shutdown or servic-
ing, energize the crankcase heaters for 24 hours before
starting the compressors.
Compressor Lockout — If any of the safeties (high-pressure,
low-pressure, freeze protection thermostat, compressor in-
ternal thermostat) trip, or if there is loss of power to the
compressors, the CLO (compressor lockout) will lock the
compressors off. To reset, manually move the thermostat
setting.
EVAPORATOR FAN MOTOR PROTECTION —A manual
reset, calibrated trip, magnetic circuit breaker protects against
overcurrent. Do not bypass connections or increase the size
of the breaker to correct trouble. Determine the cause and
correct it before resetting the breaker.
CONDENSER-FAN MOTOR PROTECTION — Each
condenser-fan motor is internally protected against
overtemperature.
HIGH- AND LOW-PRESSURE SWITCHES — If either
switch trips, or if the compressor overtemperature switch ac-
tivates, that refrigerant circuit will be automatically locked
out by the CLO. To reset, manually move the thermostat
setting.
FREEZE PROTECTION THERMOSTAT (FPT) — An
FPT is located on the top and bottom of the evaporator coil.
It detects frost build-up and turns off the compressor, allow-
ing the coil to clear. Once the frost has melted, the com-
pressor can be reenergized.
Relief Devices — All units have relief devices to pro-
tect against damage from excessive pressures (e.g., fire). These
devices protect the high and low side.
Control Circuit, 24-V — This control circuit is pro-
tected against overcurrent by a 3.2-amp circuit breaker. Breaker
can be reset. If it trips, determine cause of trouble before
resetting.
Replacement Parts — A complete list of replacement
parts may be obtained from any Carrier distributor upon
request.
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