A boiler that keeps switching off is usually protecting itself. The most common reasons are low pressure, a frozen condensate pipe in cold weather, a thermostat in the wrong place or a part that’s starting to fail. Some of these you can check in a few minutes. Others need a boiler repair from a Gas Safe registered engineer. It’s one of the most common calls I get in winter from homes around Bognor Regis and Rose Green.

Switching off or short cycling?

It helps to know which you’re dealing with.

• Switching off and staying off. The boiler stops and shows a fault code or warning light. It has locked out because something isn’t right.
• Short cycling. The boiler fires up, runs for a minute or two, turns off, then starts again. Over and over.

Both are worth sorting. Short cycling wastes gas and wears parts out faster. A lockout leaves you without heat.

Common causes you can check

Low pressure

If the pressure gauge reads below about 1 bar with the system cold, many boilers will cut out. Top it up following your manual. If it keeps dropping, there’s a leak or a faulty part somewhere, and that needs an engineer. My post on why boilers lose pressure explains the usual causes.

Frozen condensate pipe

In a cold snap, the plastic condensate pipe that runs outside can freeze. Waste water backs up, and the boiler gurgles and shuts down. If the pipe is at ground level and easy to reach, pour warm (not boiling) water over the outside section, then reset the boiler once.

Thermostat problems

A room thermostat in a warm spot, such as near a radiator, in sunlight or in a hallway above the boiler, can tell the boiler the house is warm when it isn’t. Flat batteries in a wireless thermostat can cause the same thing. Try new batteries and check where the thermostat sits.

Radiators all turned down

If most of the radiator valves are turned down or off, the boiler heats a small amount of water very quickly, gets too hot and switches off. Open up a few more radiators and see if it settles.

Causes that need an engineer

• Faulty pump. If water isn’t moving round properly, the boiler overheats and shuts down
• Blocked heat exchanger or filter. Sludge and scale restrict flow, with the same effect
• Faulty sensors or thermistors. The boiler gets the wrong reading and stops
• Fan or flue problems. If the boiler can’t clear its flue gases safely, it locks out
• Gas supply problems. Low gas pressure can make the flame fail

None of these are DIY jobs. Don’t remove the boiler casing or try to reach any parts inside. If the boiler keeps locking out after one reset, leave it off and book a Gas Safe registered engineer.

If you smell gas, open the windows, don’t use electrical switches, turn off the gas at the meter if it’s safe, leave the house and call the National Gas Emergency Service on 0800 111 999.

Boilers cutting out in Bognor Regis and Elmer

Plenty of homes on this part of the coast have their boiler in a kitchen or utility room with the condensate pipe running down an outside wall. On the exposed side of a bungalow in Elmer or Middleton on Sea, that pipe takes the full force of a cold easterly wind. That’s why frozen condensate pipes are such a common winter cause of boilers switching off here. Insulating or rerouting the pipe can help.

Frequently asked questions

Is it dangerous if my boiler keeps turning off?

Usually it’s the boiler doing its job and shutting down safely when something isn’t right. That said, a boiler that locks out repeatedly shouldn’t be ignored. If it comes with a smell of gas, sooty marks or a carbon monoxide alarm going off, switch it off and get help straight away.

Why does my boiler only cut out in cold weather?

Cold weather points to the condensate pipe first. When the outside section freezes, the boiler shuts down. It can also be the boiler working harder than usual, which shows up weak parts such as a tired pump or a partly blocked heat exchanger. If thawing the pipe doesn’t help, get the boiler checked.

How many times can I reset my boiler?

Once, if your manual says it’s safe. If the boiler runs and keeps running, keep an eye on it. If it locks out again, stop there and book an engineer. Repeatedly resetting won’t fix the cause, and with some faults it can make things worse. Note any fault code before you call.

Boiler still switching off?

If you’ve tried the simple checks and your boiler still keeps cutting out, give me a call on 07545 916929 or drop me a message and I’ll come and find out what’s causing it.