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Riello NXHM fault E8

Water flow failure

Heat pump

What it means

Water flow failure detected in the hydraulic circuit.

Likely causes

  1. Water filter needs cleaning
  2. Pump speed not set to highest
  3. High resistance in water circuit for pump
  4. Pump fuse or PCB fuse blown
  5. Water pressure at pump inlet too low
  6. Air remaining in water system during first operation causing malfunction
  7. Air trapped in water system after installation or servicing

Where to start

  1. Check if the water filter needs cleaning
  2. Make sure there is no air in the system (purge air)
  3. Check that the pump speed setting is on the highest speed

The full answer, free

  • 16 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