Carrier 38AQ034 - Manual (Page 9)

SERVICE
Capacity Control is by one electrically actuated
unloader which controls 2 cylinders. Unloader does not
require field adjustment.
Compressor Motor Protection
CIRCUIT BREAKER — A manual reset calibrated-trip
magnetic circuit breaker protects the compressor against
overcurrent. Do not bypass connections to increase size
of breaker for any reason If trouble occurs, determine
cause and correct before resetting the breaker. Circuit
breaker Must Trip Amps (MTA) are listed in Tableó,
Electrical Data.
DISCHARGE GAS THERMOSTAT — A sensor in the
discharge gas of the compressor reacts to excessively high
discharge
gas temperature and shuts off compressor.The
high temperature of discharge gas is a direct indication
of an overtemperature condition in compressor motor.
CRANKCASE HEATER — The compressor has an
electric heater located in the bottom cover, held in place
by a clip. Heater musi be tight to prevent backing out
(heater will burn out if exposed to air). The heater is
wired into compressor control circuit through a relay to
energize only when compressor shuts off. This keeps the
oil at a temperature that will prevent excessive absorption
of refrigerant during shutdown periods. Crankcase heater
is located in a lockout circuit. If crankcase heater is defec­
tive,
the compressor locks off Heat pump remains off
until corrective action is taken. This lockout circuit
cannot be reset by adjusting the thermostat.
Crankcase heater should be energized at all times when
unit is not running except during prolonged shutdown
or during servicing. In these cases, heater should be
energized for 24 hours before unit is restarted.
Fan Motor Protection — Fan motors are inherently
protected, grouped on a single circuit breaker.
Fan Adjustment — When replacing a fan, adjust fan
until top surface of hub plate is below top of orifice ring
as indicated in Fig 11. Then, tighten both setscrews,
located over the keyway of fan hub of motor shaft. Seal
recessed area of fan hub bore with Permagum to prevent
rusting.
Head Pressure Control reduces condensing capacity
under low-ambient conditions. For intermediate season
operation, fan cycling is employed. Fan no. 2 is cycled by
pressure control, with the pressure sensor located in the
liquid line. Fan no. 3 is cycled by an air temperature
thermostat (see Table 2).
Liquid Line Solenoid Valve closes when compressor
is off, and opens when compressor is on. The valve mini­
mizes refrigerant migration during heat pump OFF cycle,
protecting against flooded starts.
Accumulator Oil Return is external. The accu­
mulator drains through an extenal port at bottom of
accumulator. The port feeds an orifice which regulates the
rate of oil and refrigerant returned to the compressor. The
orifice is removable and cleanable when the system does
not
contain refrigerant. The oil return mechanism also
contains a solenoid valve that opens when compressor is
ON, and closes when compressor is OFF. The oil return
solenoid does not allow liquid refrigerant to drain from
the accumulator during the heat pump OFF cycle, pro­
tecting the compressor against flooded starts.
Lubrication
FAN MOTORS — Fan motors have permanently lubri­
cated bearings. No provisions for lubrication are made.
COMPRESSOR — The compressor has its own oil
supply. Loss of oil due to a leak in the system should be
the only reason for adding oil after system has been in
operation.
Coil Cleaning — Clean coils with a vacuum cleaner,
fresh water, compressed air or a bristle brush (not wire).
Set up coil cleaning as part of a planned maintenance
schedule
when units are installed in corrosive environ­
ments. Wash all accumulations of dirt from coil in these
applications. Keep condenser coil drain holes free of dirt
and debris to ensure adequate coil drainage.
UNIT DIMENSION A (in.)
38AO Center Fan End Fan
024 % %
028
034
1% 2%
Fig. 11 — Fan Adjustment