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Worcester Bosch Greenstar 4000 Combi fault 2948

No flame signal with low output

Gas boiler

What it means

Burner starts automatically after purging with no flame signal at low output; may be caused by strong winds.

Likely causes

  1. Strong wind effects on flue
  2. Incorrect CO2 settings
  3. Flue integrity issue
  4. Incorrect gas type
  5. Incorrect gas supply pressure
  6. Damaged or blocked flue system
  7. Incorrect gas/air ratio
  8. Faulty gas valve
  9. Misfiring ignition transformer
  10. Power supply issue
  11. Faulty electrodes or cable
  12. Faulty external gas flow monitor (natural gas)
  13. Faulty burner
  14. Faulty seals around the burner
  15. Faulty internal flue seals
  16. Faulty case seals
  17. Flue system integrity problem
  18. Combustion circuit problem
  19. Combustion fault
  20. Damaged or insecure flue joints
  21. Obstructed or damaged terminal/terminal guard
  22. Damaged flue pipes or gaskets
  23. Unauthorised modification of flue gas system
  24. Leaking flue joints

Where to start

  1. Check CO2 settings
  2. Check flue outlet position for effects of excessive wind pressure
  3. Check flue integrity

The full answer, free

  • 55 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 77), 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 Worcester Bosch manual for the Greenstar 4000 Combi. Check the model on the data plate before you order parts.

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