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Crankcase Heater — Each compressor has a crankcase heater
to prevent absorption of liquid refrigerant by oil in the crank-
case when the compressor is idle. Since power for the crank-
case heaters is drawn from the unit incoming power, main
unit power must be on for the heaters to be energized.
IMPORTANT: After a prolonged shutdown or serv-
ice job, energize the crankcase heaters for 24 hours
before starting the compressors.
EVAPORATOR-FAN MOTOR PROTECTION — A man-
ual 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. If the evaporator-
fan motor is replaced with a different horsepower motor, re-
sizing of the circuit breaker is required. Contact Carrier Ap-
plication Engineering.
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. To reset, manually move the thermostat setting.
FREEZE PROTECTION THERMOSTAT (FPT) — An FPT
is located on the evaporator coil for each circuit. It detects
frost build-up and turns off the compressor, allowing the coil
to clear. Once the frost has melted, the compressor can be
reenergized.
Relief Devices — All units have relief devices to pro-
tect against damage from excessive pressures (i.e., fire). These
devices are installed on the suction line, liquid line, and on
the compressor.
Control Circuit, 24-V — This control circuit is pro-
tected against overcurrent by a 3.2-amp circuit breaker (CB4).
Breaker can be reset. If it trips, determine cause of trouble
before resetting.
Control Circuit, 115-V — This control circuit is pro-
tected against overcurrent by a 5.0-amp circuit breaker (CB3).
Breaker can be reset. If it trips, determine cause of trouble
before resetting.
Compressor Lockout Logic — If any of the safe-
ties trip, the circuit will automatically reset (providing the
safety has reset) and restart the compressor in 15 minutes. If
any of the safeties trip 3 times within a 90-minute period,
then the circuit will be locked out and will require manual
resetting by turning off either the unit disconnect or the con-
trol circuit breaker, or opening the thermostat.
Replacement Parts — A complete list of replacement
parts may be obtained from any Carrier distributor upon
request.
Fig. 41 — Cooling Charging Chart,
Sizes 024-034
Fig. 42 — Cooling Charging Chart,
Sizes 038-048
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