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Worcester Bosch Greenstar 4000 Combi fault 284

Opening air/gas ratio control valve/oil solenoid valves

Gas boiler

What it means

Fault category O (operating message, not a fault). Gas valve is opening.

Likely causes

  1. Incorrect gas type
  2. Incorrect gas supply pressure
  3. Damaged or blocked flue system
  4. Incorrect gas/air ratio
  5. Faulty gas valve
  6. Misfiring ignition transformer
  7. Power supply issue
  8. Faulty electrodes or cable
  9. Faulty external gas flow monitor (natural gas)
  10. Faulty burner
  11. Faulty seals around the burner
  12. Faulty internal flue seals
  13. Faulty case seals
  14. Combustion fault
  15. Restricted gas supply
  16. Livestock stables or storage rooms for fertilisers near appliance
  17. Permanent ammoniac concentration in installation area

Where to start

  1. Check the gas type
  2. Check gas supply pressure against allowed table values
  3. Check the flue system; clean, repair or replace if required

The full answer, free

  • 47 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 74), 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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