Reset a boiler that has locked out

Check your boiler safely, find the reset button, and get heating and hot water working again in minutes.

RB-01Check for gas smell and working carbon monoxide alarm firstBefore touching anything, check you cannot smell gas and that any carbon monoxide alarm in the house is not sounding. If you smell gas, do not touch the boiler or any switch — turn off the gas at the meter, open windows, leave the property and call the National Gas Emergency Service on 0800 111 999. If all is clear, continue.

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Gas leaks and CO alarms are a safety emergency, not a DIY fix. Call the National Gas Emergency Service (0800 111 999) if you smell gas.

RB-02Find your boiler's fault display and manualMost boilers show a fault code or a flashing light when locked out. Find your boiler's user manual (often a PDF online if you search the model name) so you know what the code means before resetting. Write the code down — it helps if you need to call an engineer later.

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RB-03Check the pressure gaugeMany boilers lock out simply because pressure has dropped too low. Look at the pressure gauge on the front of the boiler — it should normally sit between 1 and 1.5 bar (check your manual for your exact model). If the needle is well below 1, low pressure is likely the cause and a reset alone will not fix it for long.

RB-04Press and hold the reset buttonLocate the reset button — it is usually marked with a reset symbol or the word 'reset', and is often a simple button rather than a dial. Press and hold it for the time stated in your manual, typically 5 to 10 seconds, then let go. Do not hold it repeatedly in quick succession — wait between attempts.

RB-05Watch the boiler restartAfter resetting, the display should clear and the boiler should go through its normal start-up sequence, often with a click and the sound of the pump or fan. This can take a minute or two. Stand back and let it run through — do not press reset again while it is trying to start.

RB-06Confirm heating and hot water are workingOnce the boiler settles, turn on a hot tap and check the central heating comes on if it's due to. Give it a few minutes — some boilers take a short while to fire the burner after a reset. If both work normally, the lockout is cleared.

RB-07If it locks out again, stop and call a Gas Safe registered engineerIf the same fault code returns straight away, or the boiler locks out again within a day, do not keep resetting it. Repeated lockouts usually mean a real fault — low pressure that keeps recurring, a sensor fault, or an ignition problem — and gas appliances must only be opened up and repaired by a Gas Safe registered engineer.

RULES

KNOW THE RULES

By law, only a Gas Safe registered engineer can work on gas boilers and their components. Check the engineer's Gas Safe ID card before they start.

RB-08Note the fault for the engineer if neededIf you do need to call someone, note down the fault code, the time it happened, and whether the pressure gauge was low. This saves the engineer time on the visit and can save you money on the call-out.

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Before you start: What gas work can I legally do myself?

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