York Heat Pump: YZF
Re: High Discharge Temperature Fault (Heating)
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
- Locked-out 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 O/D Expansion Valve |
| 2 |
Refrigerant Over-Charge |
|
Bad Discharge Sensor |
| 1 |
Stuck Contactor |
CHECKOUT:
1. Check Refrigerant Pressures
- Reset the control if necessary by shorting the "Test" pins.
- Hook-up refrigerant gauges to the pressure ports on the unit.
- Blue ⇒ "True Suction" Port (Not The Suction Line)
- Red ⇒ High Pressure (either refrigerant line)
- Allow the unit to run for at least 10 minutes.
- Monitor pressures as the system operates.
| Normal Pressure Range |
| Refrigerant |
0-30 Deg O/D |
30-50 Deg O/D |
| R410A |
- 75-100 Suction
- 250-320 Discharge
|
- 100-150 Suction
- 250-375 Discharge
|
2. Check Sub-Cooling
- 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 + Low Sub-Cooling (Bubbles in Sight-Glass) = Low Refrigerant Charge
- Normal Suction Pressure + High Head Pressure + High Sub-Cooling (Clear Sight-Glass) = Refrigerant Over-Charge
- Low Suction Pressure + High Sub-Cooling (Clear Sight-Glass) = Bad O/D Expansion Valve
- Examine the Outdoor Expansion Valve: An under-feeding expansion 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 both discharge sensor wires 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
- Re-Connect the R wire to the Yorkguard board.