York Heat Pump: YZF
Re: High Discharge Temperature Fault (Cooling)
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.
Qty |
Possible Causes: |
1 |
Low Refrigerant |
|
Bad I/D Expansion Valve |
|
Refrigerant Over-Charge |
|
Bad Discharge Sensor |
CHECKOUT:
1. Check Refrigerant Pressures
- Hook-up refrigerant gauges to the pressure ports on the unit.
- Allow the unit to run for 5-10 minutes.
- Monitor pressures and temperature as the system operates.
Normal Pressure Range |
Refrigerant |
55-75 Deg O/D |
75-95 Deg O/D |
R410A |
- 110 - 130 Suction
- 225 - 300 Discharge
|
- 125 - 150 Suction
- 250 - 375 Discharge
|
2. 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)
- Low Suction Pressure + High Superheat + Low Sub-Cooling (Bubbles in Sight-Glass) = Low Refrigerant Charge or Low Outdoor Air Temperature
- 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.
3. 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.
4. Check Discharge Sensor
- Disconnect power to the outdoor unit by pulling the disconnect or turning the breaker off.
- Remove 24V power from the Yorkguard board by removing the "R" wire.
- Unplug the discharge sensor from the Yorkguard board.
- Use the York Resistance Chart to check the temperature of the sensor.
- Sensor Temperature 10 deg. higher or lower than the Actual Temperature = Bad Discharge Sensor