Climatemaster - Code 4 / LT1 Fault - Heating

Article ID: 239
Last updated: 08 Feb, 2023

ClimateMaster Heat Pump: Heating

Re: Code 4 / LT1 Fault

Code 4 = Low Water Coil Temperature (FP1 or LT1)

  • The LT1 thermistor temperature must be below the selected low temperature limit setting* for 30 continuous seconds during a compressor run cycle to be recognized as a LT1 fault.
    • *JW3 Clipped = 10 deg. Unclipped = 30 deg.
  • The LT1 input is bypassed for the initial 120 seconds of a compressor run cycle.
  • LT1 is set at the factory for one try. Therefore, the control will go into lockout mode once the LT1 fault has occurred.

Qty Possible Causes:
4 JW3 Not Clipped
3 Expansion Valve Underfeeding
2 Low Refrigerant Charge
Low Water Flow
1 Stuck Compressor Contactor
Bad FP1 Sensor


1. Check JW3 Jumper

  • The JW3 jumper on the control board should be clipped in all applications with ground well piping.
  • Locate the JW3 jumper on the board and confirm that it is clipped.
    • Not Clipped ⇒ Turn off power to the unit and clip the jumper.

2. Check Operating Conditions

  • Turn the thermostat to the "Off" position and ensure that the compressor stops operating.
    • Compressor Continues to Operate = Stuck Compressor Contactor
  • Set the thermostat to call for heat and ensure that the unit is running at full capacity (Y1 & Y2 Energized).
    • If the contactor is energized but the compressor is not operating ⇒ Check for a Stuck Compressor Contactor
  • Unplug the 3-wire heater connector from the control board to prevent aux heater operation.
  • Allow the unit to operate for at least 5 minutes.
  • Check and record the HWG Inlet and Outlet Temperatures (if present).
    • Cold HWG temperatures drastically affect operating conditions and can cause excessive unit operation.
    • Make sure bottom heating element of water heater is operational and thermostat is set for approx. 120 deg.
  • Unplug the HWG pump motor (if the HWG piping is hooked-up and active).
  • Check and record the Water Pressure Drop through the geo-thermal unit.
  • Check and record the Entering Water Temperature and the Leaving Water Temperature.
  • Check and record Refrigerant Pressures.
  • Check and record the Air Temperature Rise through the unit.

► Be sure to re-connect the 3-wire heater plug and HWG pump before closing the unit!

3. 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.

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Article ID: 239
Last updated: 08 Feb, 2023
Revision: 28
Views: 2940
Comments: 0
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