E18
EHC Flame Instability / Poor Combustion

Boiler displays E18, burner shuts down shortly after ignition, often with rumbling noises.

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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

Incorrect gas pressure, Blocked burner injectors, Faulty gas valve modulation, Inadequate flue ventilation

How to Fix / Troubleshooting

Safety: This is a combustion-related fault. Only a Gas Safe engineer should adjust gas settings or work on the burner.

User checks:

  • Ensure flue terminal is clear and boiler has adequate ventilation as per EHC instructions.

Engineer checks:

  • Measure inlet and burner gas pressures and compare with EHC boiler data plate.
  • Remove and inspect the burner and injectors; clean or replace if blocked or corroded.
  • Check gas valve modulation control from the PCB and adjust using a flue gas analyser.
  • Verify flue integrity and correct installation.

Do not continue to reset the boiler if E18 persists; unsafe combustion can produce carbon monoxide.

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Repair Difficulty

Professional Required 5/5

Required Part

Gas Valve
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