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LG Therma V fault CH20

Electric heater strange overheat

Heat pump

What it means

The heater output water temperature exceeds a specific threshold, indicating the electric heater has overheated beyond safe operating limits.

Likely causes

  1. Wiring is wrong or imperfect
  2. Fuse of electric heater is blown due to overheat

Where to start

  1. Check if the harness is properly connected on PCB at CN-SOLAR. If not, connect harness properly so that it clicks into place.
  2. Remove CN-Solar connector and check open/short with a tester. If not within spec, replace Thermo switch or Electric heater.
  3. For 1Ø Model: Manually reset by pressing the button on the thermo switch.

The full answer, free

  • 11 more checks in order
  • The readings and component tests from the manual
  • How to put it right, step by step
  • The manual page for this fault (page 94), right under the answer
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Safety: Isolate the outdoor unit and any backup heater, and give the inverter capacitors time to discharge before you open the electrics. Anything on the refrigerant circuit needs F-gas certification.

From the LG manual for the Therma V. Check the model on the data plate before you order parts.

Other LG Therma V fault codes