York YHE / YHG Heat Pump: Cooling

Re: High Pressure Fault - Last Mode Heat Pump

The heat pump was running in cooling mode and the high pressure switch tripped.

A High Pressure Lockout is indicated by a 3-Flash LED pattern on the outdoor unit control board.

X/L Output

CHECKOUT:

1. Check Condenser Motor

• Set the thermostat to call for COOL.
• At the outdoor unit, confirm that the outdoor fan starts and operates properly with the compressor.
  • Fan Operates Normally → Step 2. Check Refrigerant Pressures
  • Compressor + No Fan ⇒ Check for a field-installed low ambient kit.
    • No Low Ambient + No Fan = Bad Condenser Motor or Capacitor

2. Check Refrigerant Pressures

• If the heat pump is in lockout, reset by removing 24VAC power to the outdoor control board.
• Initiate a call for COOL from the thermostat.
• Hook-up refrigerant gauges to the pressure ports on the unit.
  • Blue ⇔ "True Suction" Low Pressure
  • Red ⇔ High Pressure (small liquid line)
• Place an insulated temperature probe on the liquid line near the outdoor unit.
• Allow the unit to run for at least 10 minutes.
• Monitor pressures and temperature as the system operates.
  • If pressure exceeds Normal Range and kicks-off on Hi Pressure safety in the first 5 minutes = Bad Overcharge or No Outdoor Airflow
  • If the compressor never kicks on & the control locks-out on Hi Pressure ⇒ Suspect a Bad Pressure Switch

4. Check Sub-Cooling

• Record "Saturation Temperature" from the discharge pressure gauge.
• Subtract the Actual liquid line temperature reading.
  • Saturation Temp - Liquid Line Temp = Sub-Cooling
    • Sub-Cooling > 13 deg. + High Discharge Pressure + Normal or High Suction Pressure = Overcharged
    • Sub-Cooling > 13 deg. + High Discharge Pressure + Low Suction Pressure = Bad I/D Expansion Valve or Refrigerant Restriction
    • Sub-Cooling < 2 deg. + High Discharge Pressure + Hot Liquid Line = Low Outdoor Heat Transfer ⇒ Clean Condenser Coil and recheck pressures.