Climatemaster - Code 5 / LT2 Fault - Cooling

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.

CHECKOUT:

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