ClimateMaster Heat Pump: Cooling
Re: Code 5 / LT2 Fault
Code 5 = Low Air Coil Temperature (FP2)
- The FP2 thermistor temperature must be below the selected low temperature limit setting (30 deg. unclipped) for 30 continuous seconds during a compressor run cycle to be recognized as a FP2 fault.
- The FP2 input is bypassed for the initial 120 seconds of a compressor run cycle.
- FP2 is set at the factory for one try. Therefore, the control will go into lockout mode once the FP2 fault has occurred.
||Low Refrigerant Charge
||Expansion Valve Underfeeding
||Bad FP2 Sensor
||Low Air Flow (Filter or Coil)
||Low Air Flow (Fan Speed)
1. Check Operating Conditions
- Hook-up refrigerant gauges to the pressure ports in the unit.
- Blue ⇔ Low Pressure Port (typically the middle line of the reversing valve)
- Red ⇔ High Pressure Port (on the compressor discharge line)
- Place an insulated temperature probe on the liquid line between the indoor coil and expansion valve.
- Unplug the HWG pump motor (if the HWG piping is hooked-up and active).
- If the heat pump is in lockout, reset by removing 24VAC power to the control board.
- It can take up to 10 minutes for the heat pump to restart.
- Set the thermostat to call for cool and ensure that the unit is running at full capacity (Y1 & Y2 Energized).
- Allow the unit to run for at least 5 minutes.
- Check and record the Water Pressure Drop through the geothermal unit.
- Check and record the Entering Water Temperature and the Leaving Water Temperature.
- Check and record Refrigerant Pressures.
- Check & Record Sub-Cooling.
- Sub-Cooling = Saturation Temp (from gauge) - Liquid Line Temp
- Check and record the Air Temperature Drop through the unit.
► Be sure to re-connect the HWG pump before closing the unit.
2. Compare to Unit Performance Chart
- Use Flow Sheet to convert pressure drop to GPM and then GPM per Ton.
- Compare actual conditions to Unit Performance Chart.
- Low Suction Pressure + High Sub-Cooling + Low Air Temp Drop = Under-Feeding Expansion Valve
- Low Suction Pressure + Low Sub-Cooling + Low Air Temp Drop = Low Refrigerant Charge
- Low Suction Pressure + Normal Sub-Cooling + High Air Temp Drop = Low Air Flow
3. Check FP2 Sensor
- Turn off power to the unit.
- Unplug the FP2 sensor (Violet) from the CXM board.
- Check the resistance of the sensor & compare to Sensor/Resistance Chart (standard 10K ohm sensor)
- Compare sensed temperature to actual temperature.
- More than 5 deg. difference = Bad FP2 Sensor