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Riello NXHM fault HE

Communication error between main board and thermostat transfer board

Heat pump

What it means

Communication failure between the main board and the thermostat transfer board when RT/Ta PCB is set to valid.

Likely causes

  1. RT/Ta PCB is set to be valid on user interface but thermostat transfer board is not connected
  2. Communication between thermostat transfer board and main board is not effectively connected

Where to start

  1. Check communication wire connection between thermostat transfer board and main board
  2. Secure electrical wiring with cable ties as shown in figure
  3. Verify no external pressure is applied to terminal connectors

The full answer, free

  • 1 more check 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 65), right under the answer
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Safety: Isolate the heat pump 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 Riello manual for the NXHM. Check the model on the data plate before you order parts.

Other Riello NXHM fault codes