Biomass Boiler Common Faults & Essential Information 2018 UPDATE

Top list of the most frequent Biomass Boiler common faults & breakdowns that we get called out to which could often be simply rectified by the client.

Please adhere to all safety precautions, warning notices and wear suitable PPE (if required) when carrying out any works on Biomass Boiler systems.

Work should only be undertaken by a suitable component person.

If you are unsure about any fault with your Biomass Boiler system then please phone our 24 hour technical support team on 01228 318900

Fault 1 – Water Over Temp  – No Heat to property  (Boiler hot)  – No Circulation 

  • Check the system water pressure gauge (usually at the back of the boiler). This should be a minimum of 1  Barr pressure on a pressurised system. (see picture below)
  • Ensure all system automatic air vents are opened to expel excess air in system. (if weeping water close after air has came out)
  • Top up system pressure using system filling loop (usually a 1ft long metal braided hose with a small black lever tap on either end of it). The system pressure should be topped up to 0.5-1 Barr when cold or 1-2 Barr when hot. (see pictures below)
  • If system is still not circulation or the boiler is hot and not getting rid of the heat then the circulation pump or valves may have failed.

Fault 2 – No lights on boiler display

  • Check to see if the circuit breaker or main switch has tripped.
  • Check if boiler has an indicator light on the fused spur at the back of boiler (if installed)
  • Touch display (if touch screen) to see if the display is in sleep mode.
  • Switch power off to the boiler, wait 10 seconds, switch power on again (if the system is not burning)
  • If none of these solves the problem then you may need to check the electrical supply to the boiler and then check for lights on the man circuit board

Fault 3 – Vacuum System timed out – suction timed out (no fuel at boiler) 

  • Is vacuum motor functioning at all? (check in system relay test)
  • If vacuum motor is running but no pellets flowing check pellets in the hopper.
  • If pellet hopper is full try moving the isolating slider on the bottom of bin to agitate pellets while the vacuum is running.
  • if vacuum pipe is full of pellets remove vacuum pipe at the end closest to blockage and shake until free.
  • In recent years we have seen many vacuum pipes fail and wear through. This generally occurs on the corners on the pipe furthest from the bin. It would be prudent to check for pellet dust build up around these bends.
  • If a new pipe is required please contact us for details.

Fault 4 – System fuel/feed Auger not functioning

  • Most auger motors will have a safety trip device installed within 1.5 meters of them. Check for this device and see if device has tripped. (reset if required)
  • Carefully check to see if the motor casing is hot which could suggest that the motor is overloaded due to foreign bodies or large pieces of fuel.
  • Check fuel store for foreign bodies or large pieces of wood (especially if on chips) is these could cause augers to jam up.
  • If the motor trips a second time then check the auger for foreign bodies and ensure to avoid any moving parts that are unisolated.
  • If trip device is not installed or has not tripped then check the supply to the motor. (1ph motors can have failed capacitors inside causing poor startup, these can be replaced at a low cost)

Fault 5 – Pellets or half-burned fuel in ash chamber

  • Check to see the condition of burner grate in the boiler if visible or accessible (usually through ash chamber door or burn chamber door). Some boilers such as Solar Focus can require a replacement burner grate every 6-18 months depending on usage so it is always good to keep a replacement spare.
  • Replace grate according to boiler manual if required or attempt to close gaps and straighten grate if possible. This will stop the pellets falling through.
  • Check for the free passage of air throughout the boiler. Restriction of the emissions can cause poor combustion and lead to issues with fuel burning.
  • Check the feasibility of the temperature probes within the boiler


For any further assistance with the above scenarios or for breakdown assistance please phone our dedicated 24hr technical support and call out team on 01228 318900.