York Heat Pump: Yorkguard VI

Re: Low Discharge Temperature (Heating)

The status lights on the module will indicate as follows: Red = On, Green = 6 Flash.

• If, after energizing the compressor contactor for 1 hour, the Yorkguard module senses a compressor discharge temperature lower than 90 deg. the unit will enter a Low Discharge Temperature lockout which disables compressor operation.
• This code is intended to indicate a compressor not running, but other issues that may result in a low discharge temperature reading may be the cause.

CHECKOUT:

1. Check Outdoor Unit

• Make sure the thermostat is set correctly and calling for Heat.
  • Unit Operating →  Step 4. Check Pressures & Temperature
• Remove the access panel of the outdoor unit.
• Check for 230V inlet power on the compressor contactor.
  • No Power →  Step 2. Check Disconnect, Breaker & Compressor
  • Power Present ⇒ Check Diagnostic Light on Board
    • Diagnostic Present ⇒ Reset by removing  R  and  Y  from the board, then re-attaching.

2. Check Disconnect, Breaker & Compressor

• Confirm the disconnect switch is inserted in the "ON" position.
• Pull the service disconnect switch.
• Check resistance between each leaving leg of the compressor contactor & ground.
  • Any resistance = Electrical Short ⇒ Check Compressor Windings
  • No Short ⇒ Check Capacitor
• Check the unit breaker at the breaker panel and reset if necessary.
• (If no electrical short) Re-insert the service disconnect plug to restore power to the outdoor unit.
• Re-check for 230V on the contactor inlet.
  • No Power = Loose or Burnt Wires in Disconnect or Bad or Tripped Breaker
  • Unit comes on and operates normally →  Step 4. Check Pressures & Temperatures

3. Check Contactor

• Look for signs of burnt contacts (possible sticking contactor).
• Contactor Pulled-In + No Compressor Operation:
  • Check for 230V across the leaving legs of the compressor contactor.
    • Inlet Power + No (or low) Outlet Power = Bad Contactor
    • Inlet Power + Outlet Power + No Compressor = Compressor off on Internal Overload or Burnt Compressor Terminals
      • Check compressor winding resistance
      • Visually inspect the compressor terminals 

4. Check Pressures & Temperatures

• Turn off power to the outdoor unit by pulling the service disconnect or turning off the breaker.
• Hook-up refrigerant gauges to the pressure ports on the unit.
  • Blue --> "True Suction" Low Pressure (Not the Suction Line)
  • Red --> High Pressure (either refrigerant line)
• Hook an insulated thermistor to the compressor discharge line and monitor temperature.
• Re-apply power to the outdoor unit.
• Start the compressor with a call for heating from the thermostat.
• Allow the system to operate for at least 10 minutes.
• Observe refrigerant pressures + Discharge Temperature as the system operates.

• Normal discharge temperature = 130 to 160 deg.
  • Actual Discharge Temperature Below 100 deg. ⇒ Contact Supervisor

5. Check Discharge Sensor

• Pull the service disconnect switch.
• Power off the Yorkguard VI by disconnecting the  R  wire.
• Remove the discharge sensor wires from the board.
• Set the mulit-meter for 200K Ohms.
• Check the resistance across the sensor (see York Sensor Resistance Chart).
• Compare the sensor temperature to the actual compressor discharge temperature.
  • Sensor Temperature 10 deg. higher or lower than Actual Temperature = Bad Discharge Sensor
• Re-power the board by re-connecting the  R  wire.

► If necessary, you can disable the discharge temperature sensor and the associated fault codes. (Confirm with Supervisor first.)

• Power off the Yorkguard VI by disconnecting the  R  wire.
• Disconnect the two discharge sensor wires from the Yorkguard board (tape-off the ends).
• Re-power the board by re-connecting the  R  wire.
  • This will cause the Yorkguard to ignore the Discharge Temperature.