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Glow-worm Energy System fault F.25

Safety shutdown: flue gas temperature too high

Gas boiler

What it means

Safety shutdown triggered due to flue gas temperature exceeding safe limits

Likely causes

  1. Break in plug connection for optional flue gas safety cut-out (SCO)
  2. Break in cable harness
  3. Incorrectly installed flue without sufficient fall can cause condensate to pool, leading to flue blockage or boiler faults
  4. Leak in the flue system
  5. Flue gas recirculation in extended flue gas installations
  6. Obstructed or insufficient air supply to installation room
  7. Combustion air contaminated with sprays, solvents, chlorinated cleaning agents, paint, adhesives, ammonia compounds, dust or similar substances
  8. Chemical substances stored at installation site
  9. Installation in hairdressing salons, painter's or joiner's workshops, cleaning businesses without a separate installation room

Where to start

  1. Measure CO (ppm) and CO2 (%) at max rate and calculate CO/CO2 ratio
  2. Measure CO (ppm) and CO2 (%) at min rate and calculate CO/CO2 ratio
  3. Where possible, carry out a flue integrity check in accordance with manufacturer's instructions and confirm readings are correct

The full answer, free

  • 13 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 System. Check the model on the data plate before you order parts.

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