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Worcester Bosch Greenstar 4000 System fault 2940

System fault burner control unit

Gas boiler

What it means

Low voltage detected at burner control unit.

Likely causes

  1. Low mains voltage
  2. Faulty burner control unit
  3. Faulty ignition transformer
  4. Incorrect gas type
  5. Incorrect gas supply pressure
  6. Power supply fault
  7. Faulty electrodes/cable
  8. Faulty flue system
  9. Incorrect gas/air ratio
  10. Faulty external gas flow monitor (natural gas)
  11. Faulty air/gas ratio control valve
  12. Faulty non-return valve in burner hood assembly
  13. Faulty seals around the burner, internal flue seals or case seals causing abnormal O2/CO2 readings
  14. Flue system integrity failure
  15. Combustion circuit fault
  16. Use or storage of cleaners containing chlorine or hydrogen halide (spray cans, primers, cleaners, paint, glue) near appliance
  17. Build-up of dust

Where to start

  1. Restart appliance
  2. Check the ignition transformer function for misfiring in the Function check menu Ignition test
  3. Check the gas type

The full answer, free

  • 39 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 76), 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 System. Check the model on the data plate before you order parts.

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