How Many Times Is It Safe to Reset a Boiler Lockout?

A boiler lockout is the boiler's own safety switch. It has stopped firing because something is not right, and the reset button is there to clear a one-off interruption, not to override a fault. The safe rule is simple: reset once, and if the boiler locks out again, reset a second time only after you have made the checks below. If it keeps locking out, stop pressing reset and call a Gas Safe registered engineer¹.

Pressing reset repeatedly does not fix anything. It clears the lockout each time, the boiler tries to fire, fails, and locks out again, and you learn nothing about the cause. The fault is still there, and on a gas appliance an unexplained fault is a reason to get a qualified person to look at it, not a reason to keep trying¹.

Before you touch the button, work through the four checks that account for most lockouts an ordinary household can safely deal with: is there gas, is there power, is the pressure right, and has the condensate pipe frozen? If none of those explains it, the next step is an engineer, not another reset³.

Reset once or twice, then stop

A lockout is not a fault code in itself. It is the boiler telling you it tried to start and could not, so it shut itself down rather than keep trying. The reset clears that state and lets it attempt a start again. If the underlying cause has gone, the boiler fires and you are back to normal. If it has not, the boiler locks out again, and that repetition is the message¹.

The method depends on your boiler. On a Baxi boiler with an ON/OFF/SELECTOR switch, the maker's instruction is to turn the selector switch to the R (Reset) position, hold it for at least 5 seconds and release⁶. Other makers use a dedicated reset button, and some use a sequence on the controls. Follow your own maker's instructions, which are usually printed inside the boiler casing or in the manual.

If the boiler locks out again after two resets, treat it as a fault that needs a Gas Safe registered engineer. Network operators are clear that a boiler fault unrelated to a power cut needs a Gas Safe registered engineer to come out and take a look¹. You can find one through the Gas Safe Register website or by calling 0800 408 5500¹.

What the red light or fault code is telling you

On a Baxi boiler, a lockout is identified by the red lockout light on or flashing⁶. That light is the boiler's way of saying it has shut down safely. It is not a diagnosis. The diagnosis comes from the fault code, if your boiler displays one, or from the pattern of when the lockout happens.

The pattern matters more than the code for an ordinary household. A lockout that happens once, on the coldest night of the year, and clears on the first reset points towards a frozen condensate pipe¹¹. A lockout that follows a power cut points towards the interruption itself, and the boiler should recover on its own when electricity returns⁹. A lockout that repeats every few hours with no obvious trigger points towards a component fault, and that is an engineer's job¹.

If your boiler shows a fault code, note it down before you reset, because the code may clear when the boiler restarts. Having the code ready when you call the engineer saves a visit. Our guide to boiler fault codes, flashing lights and lockouts explains what the common codes mean.

Checks to make before you press reset

Work through these four checks in order. Each one is something an ordinary household can safely look at, and together they cover the causes you can deal with yourself.

1. Gas. Is the gas supply on? If there has been an outage and the supply has just been restored, make sure all the gas appliances in the property, including the boiler, cooker and gas fires, are turned off before you turn the gas supply back on¹². If you smell gas at any point, stop: see the warning below.
2. Power. Check the boiler's power supply first⁴. If there has been a power cut, the boiler should work without any intervention once electricity returns⁹. If it does not, check that the boiler's own switch and any fused spur are on.
3. Pressure. Check the pressure gauge. Guidance for one water company says the gauge should be at one bar⁴, and the Gas Safe Register advises checking the central heating system water pressure and topping it up if it is too low, noting that boilers can lose system pressure as they age³. Our guide to boiler pressure and our steps for repressurising a combi boiler cover this in detail.
4. Condensate pipe. In cold weather, check whether the condensate pipe has frozen¹¹. This is one of the simple, safe checks Cadent Gas suggests for minor issues caused by freezing pipes⁵.

Thawing a frozen condensate pipe safely

A frozen condensate pipe is the most common cold-weather cause of a lockout that a household can fix. The boiler produces acidic water as it condenses, and that water leaves through a plastic pipe. If your boiler has stopped working in the cold, check whether the condensate pipe has frozen¹¹.

Thaw it with a hot water bottle, starting from the outlet and working back towards the house⁵. Do not use boiling water, and do not use a naked flame. Once the pipe is clear, the boiler should fire; if it fires up it should work normally, and if it does not, try again. If the pipe remains frozen or the boiler will not fire, call a Gas Safe registered engineer or your gas supplier¹⁴.

To stop it happening again, our guide to stopping a condensate pipe freezing covers lagging and rerouting, and frozen condensate pipes covers the signs in more detail.

When a lockout means calling a Gas Safe registered engineer

Call an engineer when the boiler locks out again after two resets, when there is no obvious cause you can check, or when the fault is clearly not related to a power cut¹. If your boiler is not working but is unrelated to a power cut, you will need to contact a Gas Safe registered engineer to come out and take a look¹⁰. A gas appliance that keeps shutting itself down is telling you something is wrong inside it, and that is not a job for the reset button.

Use the Gas Safe Register to find an engineer, either at GasSafeRegister.co.uk or on 0800 408 5500¹. When they arrive, check their Gas Safe Register ID card¹⁵. Our guide to finding a Gas Safe registered engineer and checking their card walks through what the card should show.

If your boiler is serviced annually by a Gas Safe registered engineer, faults are more likely to be caught before they cause a lockout¹⁵. Our guide to boiler servicing explains what an engineer checks.

Staying warm and safe while the boiler is out

A boiler that will not fire in winter is uncomfortable rather than dangerous, provided you heat and ventilate the home sensibly. Keep warm with blankets and layered clothing, and shut the curtains and doors of unused rooms to keep the heat in¹⁸. If you use electric blankets or portable heaters, use them safely; they can be a good way to stay warm, but only if used with care¹⁹.

Check your carbon monoxide alarms while the heating is out of action. Any alarm that fails a routine test should be returned to the installer or supplier, or replaced²¹. Our guide to heating and cooking without mains power or gas covers the alternatives in detail.

If the boiler is out during a power cut as well, keep fridge and freezer doors closed, switch off appliances like straighteners and stoves, and keep a light on in one room so you know when power returns²². Check on vulnerable neighbours, and notify a friend or neighbour if you are anxious²². Our guide to power cuts covers the wider household steps.

Where to get help: your boiler maker, supplier and the gas emergency line

There are four routes to help, and which one you use depends on what has gone wrong.

• Your boiler maker. For the reset procedure and fault codes specific to your model, the maker's manual is the authority. Baxi, for example, publishes its own reset instructions⁶.
• A Gas Safe registered engineer. For any fault that survives two resets, or any fault unrelated to a power cut, this is the route¹. Call 0800 408 5500 or use GasSafeRegister.co.uk¹.
• Your energy supplier. If you do not know how to turn off your gas, electricity or water, contact your supplier²³. If your prepayment meter has run out and your supply has already stopped, your supplier has to send someone to repair or replace the meter²⁴. Our guide to prepayment meters covers emergency credit and restarting.
• The gas emergency line. For a smell of gas, call 0800 111 999¹². Our guide to the National Gas Emergency Service explains what happens next.

If you are disabled, have a health condition, or are recovering from an injury, ask your supplier about the Priority Services Register. It can give you advance notice of power cuts²⁵, and suppliers may read your meter for you²⁶. You will need to register again if you change suppliers or move home²⁷. Our guide to extra support from networks and suppliers covers what else is available.