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Glow-worm Energy Combi fault S.42

Flue non-return flap closed

Gas boiler

What it means

Status display indicating the flue non-return flap is closed.

Likely causes

  1. Flue non-return flap closed, possibly obstructing flue path
  2. Leak in the flue system
  3. Flue gas recirculation due to extended flue gas installation
  4. Obstructed or insufficient air supply to installation room, especially in cupboard installations
  5. Combustion air contaminated with sprays, solvents, chlorinated cleaning agents, paint, adhesives, ammonia compounds, dust or similar substances
  6. Chemical substances stored at installation site
  7. Installation in hairdressing salons, painter's or joiner's workshops, cleaning businesses or similar locations without a separate chemical-free installation room

Where to start

  1. Check flue non-return flap operation
  2. Measure CO content
  3. Measure CO2 content

The full answer, free

  • 15 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 51), right under the answer
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Safety: Isolate gas and power before you open the case. If you have been into the gas side, do a tightness test, and a combustion and flue check before you hand back. Gas Safe (UK) or RGI (Ireland) work only.

From the Glow-worm manual for the Energy Combi. Check the model on the data plate before you order parts.

Other Glow-worm Energy Combi fault codes