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120
110
100
90
80
70
60
50
40
30
20
10
0
0
10
20
30
Compressor Unloaded Run Time (Minutes)
*Times are approximate.
NOTE: Various factors, including high humidity, high ambient temperature, and the
presence of a sound blanket will increase cool-down times.
Fig. 98 — Recommended Minimum Cool-Down Time
after Compressor Is Stopped*
Crankcase Heater
Each compressor has a crankcase heater to prevent absorption of
liquid refrigerant by oil in the crankcase when the compressor is
idle. Since 115-v power for the crankcase heaters is drawn from
the unit control circuit, main unit power must be on for the heaters
to be energized.
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 cor-
rect it before resetting the breaker.
CONDENSER-FAN MOTOR PROTECTION
Each condenser-fan motor is internally protected against over-
temperature. They are also protected against a severe over-current
condition by manual reset, calibrated trip, magnetic circuit break-
ers on a common circuit. As with the circuit breakers, do not by-
pass connections or increase breaker size to correct trouble. Deter-
mine the cause and correct it before resetting the breaker.
HIGH-PRESSURE SWITCHES
Settings for these switches are shown in Tables 121 and 122. If ei-
ther switch trips, that refrigerant circuit will be automatically
locked out by the controls. To reset, set ALARMS
YES.
Table 121 — Pressure Switch Settings (psig)
SWITCH
High
Table 122 — Pressure Switch Settings (kPa)
SWITCH
High
Temperature Relief Devices
All units have temperature relief devices to protect against damage
from excessive pressures caused by extreme high temperatures
(i.e., fire). These devices protect the high and low side.
Control Circuit, 115-V
This control circuit is protected against overcurrent by a 10 amp
circuit breaker. Breaker can be reset. If it trips, determine cause of
trouble before resetting.
40
50
60
70
80
R.CUR =
CUTOUT
CUT-IN
650 10
500 15
CUTOUT
CUT-IN
4482 69
3447 103
Control Circuit, 24-V
This control circuit is protected against overcurrent by two
10 amp and four 3.2 amp circuit breakers. Breakers can be reset.
If a breaker trips, determine cause of trouble before resetting.
Gas Heat (48P Only)
LIMIT SWITCHES
The maximum supply-air temperature is controlled by a limit
switch located in the gas section. The limit is designed to trip at
100°F above the maximum temperature rise.
When the limit trips, 2 flashes occur on the IGC board. The gas
90
valve is deenergized. After cooling, the system will reset and fires
gas again. If four trips occur, the system shuts down into Lockout
and 4 flashes occur on the IGC board. The system must then be
manually reset by power down and power up of the unit.
LIMIT SWITCH THERMISTOR (STAGED GAS UNIT ONLY)
The limit switch thermistor is a factory-installed component. It is
located next to the lower limit switch. The limit switch thermistor
senses temperature at limit switch location and prevents the limit
from tripping while the unit is operating at low airflow.
PRESSURE SWITCH (MODULATING GAS UNITS ONLY)
This switch senses vacuum to ensure the proper function of com-
bustion induced-draft blower. It is a normally open switch set to
close on negative pressure rise. The pressure switch is located next
to ignition and modulating gas controllers in the gas section.
ROLLOUT SWITCH
This switch senses any flame or excessive heat in the main burner
compartment and deenergizes the gas valve. If this occurs, the gas
heating system is locked out (7 flashes on IGC board) until the
rollout switch is reset manually. Reset rollout switch manually by
powering down and powering up of the unit.
When the rollout switch trips, it usually indicates a flue block-
age. Inspect the unit for any obstruction in the flue system, for
holes in the flue box, a defective hall effect sensor or pressure
switch, a defective inducer motor, or a loose combustion blower.
Compressor Removal
All compressors can be removed from the compressor side of the
unit.
IMPORTANT: All compressor mounting hardware and support
brackets removed during servicing must be reinstalled prior to
start-up.
1.
Disconnect power to unit; lockout power to compressor.
2.
Close suction and discharge service valves.
3.
Relieve refrigerant pressure into a refrigerant recovery
system.
4.
Disconnect power wires at terminal box and disconnect
conduit.
5.
Disconnect wires from crankcase heater.
6.
Lift compressor off mounting bolts and remove.
Compressor Replacement
Perform the following:
1.
Reverse procedure in Compressor Removal section.
2.
Leak-check and evacuate system, recover refrigerant.
3.
Recharge system per pre-start-up and start-up sequences.
Recheck oil levels.
4.
Energize crankcase heater for 24 hours prior to restart of
system.
185
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Troubleshooting
