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Riello NXHM fault EA

Discharge temperature sensor (tp) error

Heat pump

What it means

Fault with the compressor discharge temperature sensor Tp (note: listed remedy text matches communication fault wording, likely a table formatting error in the source manual).

Likely causes

  1. Wire doesn't connect between main control board PCB B and main control board of hydraulic module
  2. Communication wire sequence is not right
  3. High magnetic field or high power interference
  4. Inlet water temperature too low
  5. Ambient temperature too low causing target leaving water temperature to be too high
  6. T5 (DHW tank temperature) too low or ambient too low causing target T5 too high
  7. Rapid temperature change during initial heating of underfloor heating screed

Where to start

  1. Connect the wire
  2. Reconnect the wire in the right sequence
  3. Check for nearby interference sources

The full answer, free

  • 4 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 66), 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