E17
Remeha Sensor mismatch / temperature differential error

Boiler shows E17 and cycles on and off rapidly

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Flow and return sensors reading unrealistic difference, Air lock in primary circuit, Blocked or partially blocked heat exchanger, Pump running at incorrect speed

How to Fix / Troubleshooting

Safety first: Allow the boiler to cool before bleeding or opening any components.

  • Bleed system thoroughly: Remove air from radiators and any high points. Re-pressurise the system as needed.
  • Check pump setting: On models with adjustable pump speed, ensure the pump is set according to system requirements (usually medium or auto).
  • Engineer tasks: Compare flow and return NTC readings via diagnostics, clean or flush the primary heat exchanger if blocked, and verify correct pump operation and sizing.
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Repair Difficulty

Hard 4/5

Required Part

Primary Heat Exchanger
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