What to check if a boiler is working but with visible smoke?

If an oil boiler is working but there is visible smoke from the flue or a high smoke number, heating engineers should check the following. Please note, it is important to always isolate the electricity supply to the boiler before working on the boiler. 

  • Check whether there is insufficient air supply - check the air damper setting and the condition of the fan.
  • Check that the room ventilation is adequate - please refer to the Boiler Installation Manual.
  • Check the nozzle size and type.
  • Check the fuel pressure which may be too high - please check and adjust if required. 

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