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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 loca-
tion and prevents the limit from tripping while the unit is oper-
ating at low airflow.
PRESSURE SWITCH (Modulating Gas Units Only) —
This switch senses vacuum to ensure the proper function of
combustion 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 ex-
cessive 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
blockage. Inspect the unit for any obstruction in the flue sys-
tem, for holes in the flue box, a defective hall effect sensor or
pressure switch, a defective inducer motor, or a loose combus-
tion blower.
Compressor Removal — All compressors can be re-
moved from the compressor side of the unit.
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.
IMPORTANT: All compressor mounting hardware and
support brackets removed during servicing must be rein-
stalled prior to start-up.
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