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How to reset a boiler

Has your boiler suddenly stopped working? There’s no central heating or hot water, and you don’t know why? On average one in five UK boilers will break down every year, but there’s no need to panic yet, it may just need a quick reset.

It’s likely that your boiler has just gone into ‘lockout’, which means that it has shut itself down because it detected a problem. It’s relatively common, and the good news is that you probably won’t have to call an engineer to carry out repairs, we’ll show you here how to reset it yourself and get your boiler working again.

Why is my boiler not firing up?

Boiler lockout happens for a number of reasons – it’s a safety feature that’s designed to activate when something goes wrong.

If your boiler has gone into lockout mode, you may see flashing red or green lights or an error code on the display screen. They often start with an ‘E’ or ‘F’ and you should read your boiler’s manual to work out exactly what the code means.

Before we guide you through how to rest your boiler, here are some of the most common issues that may have caused your boiler lockout, how to spot them and how you can potentially fix them.

High or low pressure

Your boiler might lockout and show an error code if the water pressure is too high or too low.

Around 80 per cent of modern boilers are combination boilers, which can’t function properly if the pressure isn’t within set parameters.

You can find out if pressure is the problem simply by reading your boiler pressure gauge. Normally it should be around 1.5 bar – and anything below 1 bar is regarded as low pressure.

If the gauge is lower than 1, check through your boiler manual for precise instructions on how to repressurise your boiler.

Your combi boiler gauge needle is pointing up towards 2.5 bar, then your pressure is too high. It’s sometimes possible to rectify this by bleeding your home’s radiators. If that works then your boiler shouldn’t need a reset. But if it still reads around the 2.5 mark, it’s time to call a Gas Safe professional to carry out a boiler repair.

Debris or sludge in your system

Another reason your boiler could lockout is a build-up of debris in the system. Limescale, rust and sludge can stop the heat exchanger and other key parts of your boiler from working properly.

Limescale can really impact boiler efficiency, in some cases by up to 12%. You may notice the problem when your boiler starts to sound noisier and clankier than usual. The best way keep your boiler working and avoid having to reset is to clear out the heating system pipes with a power flush.

Ignition problems

Most modern boilers will lockout if they fail to ignite three consecutive times. Some of the reasons boilers don’t ignite first time could include:

  • Lack of gas pressure
  • Trouble with your ignition lead
  • A fault with your gas valve

If your boiler is still not igniting first time after resetting, you should call a Gas Safe-registered engineer to fix the problem.

If the pilot light on your boiler frequently goes out, or there are sooty-looking stains around your gas appliances, this could indicate a carbon monoxide leak. Carbon monoxide poisoning can be lethal and needs to be fixed immediately. Call a heating engineer, open your windows and doors and do not use the appliance in the meantime.

Finally, if you have a condensing boiler and the weather is very cold, your external condensate pipe could have frozen. Sensors in the boiler will detect the pipe is blocked and stop the boiler from operating. This will need to be thawed out before your boiler will restart.

Is it safe to reset your boiler?

If you’ve checked the electricity and gas supply are both still on and your boiler pressure gauge appears normal, then you may need to reset your boiler. Don’t worry, resetting your boiler is a very simple and safe procedure.

Where is the reset button on a boiler?

Once you’ve located the problem, it’s time to reset the boiler to get your central heating and hot water back in business.

If you don’t know how to reset a boiler, for most models all you need to do is press and hold the reset button for up to 10 seconds. Precisely where your boiler’s reset button is located will depend on the model, so you should refer to your manual here if you’re unsure.

You’ll know that the reset procedure has worked if you see one or all of the following:

  • The error code/fault code disappears
  • A red or orange light turns green
  • The flame ignites
  • A ‘burner’ light turns on

You should hear your boiler fire up again. In order to test if your boiler is now working properly, just create a demand for hot water or heating by opening a hot tap or turning up the thermostat.

Why won’t my boiler turn on after resetting?

Remember, resetting is probably not a long-term solution to your gas boiler problems – it’s simply a quick way to reboot your boiler when a problem has caused it to lockout.

If your boiler reset button isn’t working, check the power and pressure again. Once you’ve tried fixing the problem and resetting a couple of times, if the boiler still isn’t playing ball, it’s time to call a qualified engineer.

If you keep experiencing boiler lockout

If you ask yourself ‘why do I have to keep resetting my boiler every few days?’ then there could be something more seriously wrong with your heating system.

If you’re repeatedly getting error codes and boiler lockouts after you reset it, then consider calling a Gas Safe boiler engineer. And it might also be time to start considering a boiler replacement.

Is it time for a new boiler?

Over time, a new boiler could save you money as it’s likely to be more energy-efficient. Gas boilers that are more than 10 years old will be wasting a lot of energy and just aren’t as efficient when it comes to heating your home or business. Paying for repeated repairs to an old, unreliable boiler can be a huge waste of time and money. You can resolve this by removing your old model and replacing it with a more cost-effective new boiler. Find out more here.

Are you looking for a professional and reliable boiler repair service in Leeds? Woolfoot Heating can service, maintain and repair all types of boiler, no matter how old. With our industry knowledge and expertise, we can diagnose problems, answer any questions you might have and offer you the right boiler solution. We also offer Yorkshire’s longest new boiler guarantee. Find out more here. Call Woolfoot Heating on 0330 113 8555 or email

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