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Worcester Bosch Greenstar 4000 Combi fault 2927

Flame failed during burner operation

Gas boiler

What it means

No ionisation detected after ignition; flame failure during burner operation.

Likely causes

  1. Main shut-off valve closed
  2. Appliance isolation valve closed
  3. Low gas supply pressure
  4. Faulty flame sense electrode/lead
  5. Blocked venturi/injector
  6. Poor earth connection
  7. Damaged ignition cable
  8. Faulty gas valve
  9. Incorrect CO2 settings
  10. Flue system fault
  11. Insufficient combustion air supply
  12. Heat exchanger deposits on flue gas side

Where to start

  1. Check the main shut-off valve, open if necessary
  2. Check the appliance isolation valve, open if necessary
  3. Measure the gas supply pressure at the rated heat input

The full answer, free

  • 10 more checks in order
  • 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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