Boiler Lockouts and Fault Codes

Things you can try yourself to get your boiler back up and running.

When a boiler locks out or displays a fault code, there are some basic checks that you can perform yourself.

However, If these checks don't resolve the issue, contact us on 01382 50 50 92 and one of our professional engineers can diagnose and fix the problem effectively.


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Power Supply

Check if the boiler has power by ensuring that the power switch is on and that the fuse hasn't blown.

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System Pressure

Check the pressure gauge to ensure it's within the normal range (1-1.5 bar). If the pressure is too low, you can try repressurising the system following the manufacturer's instructions.

Boiler Lockout

When an oil boiler locks out, it typically means there was an issue with the burner and has shut down for safety reasons. To reset the burner, locate and press the reset button. This usually is red or flashes when the fault occurs.

If the boiler continues to lockout after 2-3 attempts, or there is any unusual sounds or smells coming from the boiler, contact us so one of our engineers can inspect and repair the boiler.

Frozen Condensate

Another common issue could be a frozen condensate pipe, especially during colder months. You can try thawing the pipe using warm (not boiling) water. It's also important to check if there are any error codes displayed on the boiler and consult the manual to understand what they mean.

Overheat Thermostat

Resetting an overheat thermostat on an oil boiler is a relatively simple process that can help restore proper functionality to your heating system. First, locate the reset button on your boiler, this can be found in your boiler manual. Press and hold the reset button for a few seconds until you hear a click. This action will reset the overheat thermostat and allow the boiler to restart.


Before attempting to reset the overheat thermostat, it's important to identify and address the root cause of the overheating issue to prevent future problems. Common causes of overheating in boilers include airlocks, low water pressure, or a faulty pump. If the issue persists after resetting the thermostat, it may be necessary to contact one of our engineers for further inspection and repairs.