York Heat Pump: Cooling

Re: Hi Pressure Fault + Hi Discharge Temperature Fault

When checking the fault history, the Yorkguard VI shows both a High Pressure and High Discharge Temperature fault.

A High Pressure Lockout is indicated by the following LED pattern on the outdoor unit control board:

• Green = Off
• Red = 1 Flash (Not in Lockout) or 2 Flashes (Lockout)

A High Temperature Lockout is indicated by the following LED pattern on the outdoor unit control board:

• Green = 5 Flashes
• Red = On

X/L Output

• 2 Flashes at Thermostat = Soft Lockout
  • Switch opened two times in 6 hours.
  • Reset by cycling thermostat or jumping Test pins.
• 3 Flashes at Thermostat = Hard Lockout
  • Four Soft Lockouts in 12 hours.
  • Reset by cycling 24VAC power to the board.

CHECKOUT:

1. Check Outdoor Unit

• Make sure the thermostat is set correctly and calling for Cool.
  • Unit Operating → Step 2. Check Contactor
• Remove the access panel of the outdoor unit.
• Check the Yorkguard VI for any active diagnostics.
  • Reset if necessary by removing 24V  R  and  Y  from the board, the reconnecting.
    • Speed-up the Anti Short-Cycle Delay timer by jumping the Test pins.

2. Check Contactor

• Cycle power to the contactor by removing the wire from the "M" or "M1" terminal on the Yorkguard VI board.
  • If the contactor fails to disengage = Stuck Contactor
• Disconnect high voltage power to the outdoor unit by pulling the service disconnect.
• Look at the contact points of the contactor to see if the contactor is burnt and might be sticking.

3. Check Refrigerant Pressures

• Hook-up refrigerant gauges to the pressure ports on the unit.
• Allow the unit to run at least 10 minutes.
• Monitor pressures and temperature as the system operates.

4. Check Superheat and Sub-Cooling

• Superheat
• Check the Suction Line Temperature near the outdoor unit.
• Record the "Evaporation Temperature" from the Suction pressure gauge.
  • Superheat = Suction Line Temperature - Evaporation Temperature
    • Normal Superheat = 8 - 18 deg.
• Sub-Cooling
• Check the Liquid Line Temperature near the outdoor unit.
• Record "Saturation Temperature" from the discharge pressure gauge.
  • Sub-Cooling = Saturation Temp - Liquid Line Temp
    • Normal Sub-Cooling = 3 - 12 deg. (Sight-Glass Clear)
• Normal Suction Pressure + Normal Superheat + High Head Pressure + High Sub-Cooling (Clear Sight-Glass) = Refrigerant Over-Charge
• Low Suction Pressure + High Superheat + High Sub-Cooling (Clear Sight-Glass) = Bad I/D Expansion Valve
  • Examine I/D Expansion Valve: An under-feeding valve should be frosting at the valve.

5. Check Discharge Temperature

• Connect a temperature thermistor to the compressor discharge line near the discharge sensor.
• Allow the system to run for about 10 minutes and watch the actual discharge temperature.
  • Normal Discharge Temperature = 130 - 180 deg F.
  • Trip Point = 250 deg. F.