186
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 (48N 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
valve is de-energized. After cooling, the system will reset and
fires gas again. If 4 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 pre
-
vents 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
combustion induced-draft blower. It is a normally open switch
set to close on negative pressure rise. The pressure switch is lo
-
cated next to ignition and modulating gas controllers in the gas
section.
ROLLOUT SWITCH
This switch senses any flame or excessive heat in the main burn
-
er 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 manual
-
ly 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, 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.
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.
Содержание WeatherExpert 48N2
Страница 135: ...135 Fig 18 48 50N Typical Power Schematic Nominal 075 Ton Unit Shown ...
Страница 136: ...136 Fig 19 48 50N Typical Power Schematic Nominal Ton 90 150 Units Shown ...
Страница 137: ...137 Fig 20 48 50N Main Base Board Input Output Connections ...
Страница 138: ...138 Fig 21 48 50N RXB EXB CEM Input Output Connections a48 9307 ...
Страница 139: ...139 Fig 22 48 50N EXV SCB Input Output Connections a48 9308 ...
Страница 140: ...140 Fig 23 48N Typical Modulating Gas Heat Unit Control Wiring ...
Страница 141: ...141 Fig 24 50N Typical Electric Heat Unit Control Wiring ...
Страница 144: ...144 Fig 27 48N Typical Gas Heat Section Wiring Nominal Ton 120 to 150 Units ...
Страница 145: ...145 Fig 28 48 50N Typical Power Component Control Wiring 460 v ...
Страница 146: ...146 Fig 29 48 50N Component Control Wiring 575 v Nominal Ton 075 to 150 Units ...
Страница 147: ...147 Fig 30 48 50N Component Arrangement Power Box ...
Страница 148: ...148 Fig 31 48 50N Component Arrangement Control Box ...
Страница 168: ...168 Fig 47 Sensor and Ignition Position Fig 48 Combustion Blower Details SENSOR DETAILS IGNITION DETAILS ...
Страница 240: ...240 APPENDIX D VFD INFORMATION CONT Fig G VFD Bypass Wiring Diagram WHEN USED ...