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How to reset a boiler

two people sat on a wall talking

What you'll learn

  • Where is the boiler reset button?
  • How to reset a boiler
  • Why won’t my boiler turn on after resetting?
  • Why you might need to reset your boiler
  • How do you reset a boiler when the gas runs out?

If a boiler detects a fault, it will shut itself down as a safety precaution (also known as a ‘lockout’). In terms of protection, this is an ideal way to stop unnecessary damage to your central heating system, though it can be frustrating if you’re not sure what to do next. Most importantly, you’ll need to know how to reset the boiler in order to gain back your heating and hot water.

Keep reading to find out how to reset a boiler and common reasons which may be causing your boiler to lockout.

boiler in the kitchen cupboard with other kitchen appliances

Where is the boiler reset button?

To reset your boiler, you’ll first need to locate the boiler reset button. The most common place to look will be close to the display screen, however some boilers will use a reset dial rather than a button, so make sure to check your instruction manual for specifics.

How to reset a boiler

Before attempting to reset your boiler, you must first make sure that you have resolved the cause of the lockdown. This can be found by checking boiler error code on the display screen and using your instruction manual to understand what issue the code represents. Aside from very minor fixes (defrosting your condensate pipes, bleeding your radiators, or topping up the pressure), all errors should be looked at by a Gas Safe Registered (GSR) engineer.

Once you’re satisfied that the issue has been fixed, you can complete the following steps:

  • Find the boiler reset button
  • Press and hold the reset button for no more than 10 seconds
  • Check if the flame has ignited or to see if the error code has disappeared
  • Test the boiler is working by checking the hot water or turning up the temperature

How to reset a Vaillant boiler

For a Vaillant boiler in particular, you will need to follow the same steps as above, with the only difference being how long you need to press the reset button.

The reset button is located on the boiler’s display and will likely show a flame with a line crossed through it. You will only need to press the reset button for three seconds before the boiler resets and the display screen should change.

It’s recommended to always check your Vaillant boiler manual, as some models may have slightly different reset instructions.

Why won’t my boiler turn on after resetting?

Some boilers will take several minutes to reset or may even require two attempts. If your boiler doesn’t turn on after resetting, or the error code is still in place, you will need to contact a Gas Safe registered engineer.

Why you might need to reset your boiler

If you’ve managed to successfully reset your boiler without any further issues, that’s great - you may have experienced just a minor error or fault. On the other hand, your boiler shutting down can be a sign of significant or serious issues which need to be addressed to avoid damage or further lockouts.

In particular, if you notice that you regularly need to reset your boiler, this should not be the case. Get in touch with a Vaillant installer to find the reason behind the frequent lockouts.

  • Ignition failure or gas supply

    A reason for a boiler lockout could be the gas supply or ignition failure. This could be due to several reasons, though the most common are blockages in the flue, a faulty gas valve, or an issue with the ignition lead itself. Before resetting the boiler, a GSR engineer will need to take a look at the issue.
  • Low pressure

    If the water pressure drops to below 1.5 on your pressure gauge, your pressure is too low. Luckily, this is something you may be able to resolve yourself. You’ll need to repressurise your boiler by following the instructions within the system’s manual. If you have identified a leak, however, this will need to be resolved by a GSR engineer.
  • High pressure

    If your pressure gauge is showing a reading of above 2.5, your pressure is too high. This can be resolved by bleeding the radiators and may not require you to reset your boiler at all. If this fails to fix the issue, you will need to contact your local GSR engineer.
  • Boiler overheating

    Blockages in the system or a failed pump can cause the water to rise above a certain temperature and overheat the boiler. As a safety precaution, the boiler will automatically shut down. Unfortunately, these issues will need to be addressed by a qualified professional and you should not try to resolve this on your own.

How do you reset a boiler when the gas runs out?

If you’re on a pay-as-you-go meter, your boiler may have shut down as you have run out of gas. This isn’t a problem and the same steps can be taken to reset your boiler as soon as you have topped up your meter. In most cases, emergency gas can be added to your meter if necessary.


  • Boilers require resetting after they shut themselves down for safety precautions
  • Error codes must be addressed before resetting the system
  • Resetting usually requires holding down a button for a matter of seconds
  • If your boiler still doesn’t work after resetting, contact a GSR engineer
  • Your boiler may need resetting due to a wider, serious issue which needs resolving by a professional