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Riello NXHM fault ED

Inlet water temp. sensor (Tw_in) malfunction

Heat pump

What it means

Fault with the inlet water temperature sensor Tw_in.

Likely causes

  1. Sensor resistance out of range
  2. Tw_in sensor connector loosened
  3. Tw_in sensor connector wet or has water ingress
  4. Tw_in sensor failure
  5. Volume of tank too small
  6. Location of water temperature probe (T5) not high enough
  7. Rapid temperature change during initial heating of underfloor heating screed

Where to start

  1. Check the resistance of the sensor
  2. Check if Tw_in sensor connector is loosened
  3. Check if connector is wet or has water in it

The full answer, free

  • 9 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 64), 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