Glow-worm Incomplete combustion / flue gas spillage

Furnace flue terminal shows staining or soot marks on wall

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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

Blocked or misaligned flue on Glow-worm furnace, Incorrect burner setting, Damaged heat exchanger, Poor ventilation (for open-flue models)

How to Fix / Troubleshooting

Danger: Sooting indicates serious combustion issues and potential CO risk. Turn off the appliance and do not use it.

User steps:

  • Switch off the furnace at the isolator and gas supply if safe.
  • Ventilate the area and avoid using the appliance until inspected.

Technician steps:

  • Inspect flue system for blockages, damage, or incorrect installation.
  • Check burner and heat exchanger for damage or blockage.
  • Perform full combustion analysis and rectify any issues.
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Repair Difficulty

Professional Required 5/5

Required Part

Flue System / Burner / Heat Exchanger
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