What to Do When Your Biomass Boiler Stops Working

First: Don't Panic

A biomass boiler that has stopped working is inconvenient, but in most cases it has shut down for a reason it can communicate clearly. Modern biomass boilers have sophisticated self-diagnostic systems and will display a fault code or alarm condition that tells you — or your engineer — exactly what triggered the shutdown.

Before you pick up the phone, work through the checks below. Many boiler shutdowns can be resolved by the operator without an engineer call-out, saving time and money.

Step 1: Check the Fault Code

Go to the boiler's control panel. Every biomass boiler with an electronic controller will display a fault code, error number, or alarm message when it shuts down on a fault. This is the single most important piece of information you can have.

Write down:

• The fault code or error message (photograph the screen if possible)
• The time the fault occurred if the display shows it
• Any recent changes — new fuel delivery, recent weather, anything unusual

Your boiler manual should contain a fault code reference table. If you cannot locate the physical manual, search for it online using the boiler make, model, and the term "fault codes" — most major manufacturers publish their manuals publicly.

Common fault code categories include:

• Fuel feed faults (auger errors, hopper empty, overload): Problems with fuel getting from the store to the burner
• Ignition faults: The boiler tried to light and failed within the permitted attempts
• Temperature faults: A high-limit thermostat, safety thermostat, or over-temperature condition has triggered
• Flue/draught faults: Insufficient or excessive draught in the flue circuit
• Sensor faults: A probe or sensor is reading outside expected parameters
• Communication faults: A component is not communicating correctly with the controller

Knowing which category your fault falls into guides your next check.

Step 2: Check the Fuel Level and Auger

Fuel feed problems are among the most common causes of unplanned shutdowns. Before assuming a mechanical failure, check:

• Fuel store level: Is there fuel in the hopper or store? An empty hopper is an obvious cause of a fuel feed fault, but it is surprisingly easy to miss — particularly in a large store where the surface looks full but the outlet is clear.
• Hopper or auger inlet: Is there an obvious blockage at the point where fuel enters the auger? In pellet systems, check for caked or swollen pellets around the inlet. In chip systems, check for bridging (chip locking together and forming an arch over the outlet).
• Auger reset: Some auger systems have a manual reset button on the motor overload relay. If the auger overloaded and tripped, the motor will not run until the relay is reset — the boiler will keep reporting a fuel fault even though the blockage has been cleared. Check your manual for the location of the motor overload reset.

If there is clearly fuel available and the auger appears clear, move on without manually forcing anything.

Step 3: Check Flue Draught

Some boilers shut down on insufficient draught — the negative pressure in the flue that draws combustion gases up and away from the boiler. Poor draught can be caused by:

• A blocked flue terminal (bird nest, debris, ice in very cold weather)
• A blocked flue draught stabiliser
• Wind conditions causing back pressure at the terminal

If your boiler has a draught fault code, inspect the flue terminal externally — at a safe distance — to check for obvious obstruction. Do not attempt to work at height unless you have appropriate access equipment and training.

Step 4: Try a Controlled Reset

Once you have checked the above and there is no obvious unresolved cause (empty hopper, blocked auger, visible flue obstruction), a controlled reset is the next step.

Most biomass boilers have a reset procedure:

1. Acknowledge the fault on the control panel to clear the alarm
2. Allow the boiler to complete any active cooling or purge cycle — do not interrupt mid-cycle
3. Restart the boiler from the main start command
4. Observe the startup sequence — watch the auger, listen for ignition, observe the display

If the boiler starts and reaches operating temperature without faulting again, make a note of the fault code and when it occurred. Mention it at your next service. A single isolated fault that does not recur may be a transient condition, but it is worth recording.

If the boiler faults again on the same code, or faults on a different code after the reset, do not continue resetting repeatedly. Repeated resets on an unresolved fault can cause secondary damage — for example, repeating ignition attempts with a blocked combustion chamber packs unlit fuel into the burner pot.

Step 5: Know When to Call an Engineer

Call a qualified biomass engineer when:

• The fault code indicates a safety device has triggered (high-limit thermostat, pressure relief valve, overheat condition)
• The boiler has faulted on the same code two or more times after reset
• There is visible smoke coming from around the boiler casing or from places it shouldn't
• There is a smell of burning material (other than normal wood combustion smell)
• The boiler is making an unusual noise (grinding, scraping, or banging)
• You are unsure what the fault code means or what caused it
• The boiler is over 12 months since its last service

Response Times to Expect

For non-emergency faults where the building still has some heating (from a backup system, warm climate, or thermal mass), a response within 24–48 hours is standard from most service engineers.

For genuinely urgent situations — a care home, a property in freezing weather without any alternative heat source, a commercial kitchen with process heating down — contact your service provider on their emergency or out-of-hours number. Reputable biomass service engineers maintain an out-of-hours callout service for exactly these situations.

When you call, have the following ready:

• Boiler make, model, and output (kW)
• The fault code displayed
• A brief description of what happened — what you noticed, when, and what you have already checked
• Your location and any access notes (locked gates, livestock, etc.)

This information allows the engineer to bring the right parts and plan the visit efficiently. A service call where the engineer arrives without knowing the fault code or system spec is slower and potentially more expensive than one where you have provided good information upfront.

After the Engineer Attends

Ask for a written report of what was found, what was done, and any advisory items. If a part was replaced, ask what caused it to fail — component failure without an explanation may indicate an underlying condition that should be addressed. Keep the report with your service records.

If your boiler is registered under the RHI and has been out of service for a period, you do not need to notify Ofgem for short breakdowns — but if the fault has affected your metering or heat generation records, keep your own notes and flag it to your adviser if needed.