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Worcester Bosch Greenstar 4000 Combi fault 228

Flame signal without flame present

Gas boiler

What it means

Locking fault (Category V). Flame signal detected by control when no flame is actually present.

Likely causes

  1. Damaged ceramic insulator causing spark to earth
  2. Flame sense electrode/lead failure
  3. Faulty earth tags on boiler or electrodes
  4. Siphon fault causing water collection in sump
  5. Faulty gas valve
  6. Faulty control unit or burner control unit
  7. Incorrect gas type
  8. Incorrect gas supply pressure
  9. Damaged or blocked flue system
  10. Incorrect gas/air ratio
  11. Misfiring ignition transformer
  12. Power supply issue
  13. Faulty electrodes or cable
  14. Faulty external gas flow monitor (natural gas)
  15. Faulty burner
  16. Faulty seals around the burner
  17. Faulty internal flue seals
  18. Faulty case seals
  19. Combustion fault
  20. Restricted gas supply
  21. Livestock stables or storage rooms for fertilisers near appliance
  22. Permanent ammoniac concentration in installation area

Where to start

  1. Check the ceramic insulator is not damaged, twist and pull to ensure it is not broken.
  2. Check the flame sense and the lead and replace if required.
  3. Check the earth tags on the boiler and on the electrodes.

The full answer, free

  • 51 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 72), 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.

Other Worcester Bosch Greenstar 4000 Combi fault codes