Compressor fault and lockout

Card Set Information

Author:
garfigator
ID:
223127
Filename:
Compressor fault and lockout
Updated:
2013-06-09 16:16:30
Tags:
Troubleshooting
Folders:

Description:
Compressor
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  1. Thermostat demand signal Y1 is present, but compressor not running.
    • 1. Compressor protector is open
    • - check for high head pressure
    • - check compressor supply voltage

    2. Outdoor unit power disconnect is open

    3. Compressor circuit breaker or fuses is open

    4. Broken wire or connector is not making connect

    5. Low or high pressure switch open if present in the system

    6. Compressor contractor has failed to close
  2. Compressor is running extremely long run cycle.
    1. Low refrigerant charge

    • 2. Evaporator blower is not running
    • - check blower relay coil and contacts
    • - check blower motor capacitor
    • - check blower motor failure or blockage
    • - check evaporator blower wiring and connectors
    • - check indoor blower control
    • - check thermostat wiring for open circuit 

    • 3. Evaporator coil is frozen
    • - check for low suction pressure
    • - check for excessively low thermostat setting
    • - check evaporator airflow (coil blockages or return air filter)
    • - check ductwork or registers for blockage

    • 4. Faulty metering device
    • - check TXV bulb installation (size, location, and contact)
    • - check if TXV/FIXED orifice is stuck closed or defective

    5. Condenser coil is dirty

    6. Liquid line restriction (filter drier blocked if present)

    • 7. Thermostat is malfunctioning
    • - check thermostat sub-base or wiring for short circuit
    • - check thermostat installation (location and level)
  3. Indicates the compressor protector is open or missing supply power to the compressor
    • 1. High head pressure
    • - check high pressure switch if present in system
    • - check if system is overcharged with refrigerant
    • - check for non-condensable in system

    • 2. Condenser coil poor air circulation (dirty, blocked, damaged)
    •  
    • 3. Condenser fan is not running
    • - check fan capacitor
    • - check fan wiring and connector
    • - check fan motor for failure or blockage

    4. Return air duct has substantial leakage
  4. Compressor is running less than three minutes
    1. Thermostat demand signal is intermittent

    2. Time delay relay or air conditioner control is defective

    3. If high pressure switch is present see flash code information
  5. Compressor has a locked out due to run capacitor short, bearings are seized, excessive liquid refrigerant
    1. Run capacitor has failed

    • 2. Low line voltage (contact utility if voltage at disconnect is low)
    • - check wiring connections

    3. Excessive liquid refrigerant in the compressor

    4. Compressor bearings are seized
  6. Compressor has an open circuit due to power disconnection, fuse is open or other similar conditions
    1. Outdoor unit power disconnect is open

    2. Unit circuit breaker or fuse is open

    • 3. Unit contactor has failed to close
    • - check compressor contactor wiring and connectors
    • - check for compressor contactor failure (burned, pitted, or open)
    • - check wiring and connectors between supply and compressor
    • - check for low pilot voltage at compressor contactor coil

    4. High pressure switch is open and requires manual reset

    5. Open circuit in compressor supply wiring or connections

    6. Unusually long compressor protector reset time due to extreme ambient temperature

    • 7. Compressor windings are damaged
    • - check compressor motor winding resistance
  7. Current not sensed by start transformer
    1. Run capacitor has failed

    • 2. Open circuit in compressor start wiring or connections
    • - check wiring and connectors between supply and the compressor S terminal

    • 3. Compressor start winding is damaged 
    • - check compressor motor winding resistance
  8. Current not sensed by run transformer
    • 1. Open circuit in compressor start wiring or connections
    • - check wiring and connectors between supply and compressor R terminal

    • 2. Compressor start winding is damaged
    • - check compressor motor winding resistance
  9. Compressor always runs
    1. Compressor contactor failed to open

    2. Thermostat demand signal not connected to module
  10. 24VAC is below 18VAC
    1. Control circuit transformer is overloaded

    • 2. Low line voltage (contact utility if voltage at disconnect is low)
    • - check wiring connections

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