Boiler Lockout Main Reasons and How To Fix Boiler Lockouts

A boiler lockout is a safety feature which will only kick in if there is something wrong with your boiler. The problem is that your boiler can lockout for a variety of different reasons. Lots of people struggle to work out what the problem is and the best way to fix it. In this guide, we will explain the main reasons why boilers lockout and advise you on the best course of action to take.

If your boiler decided to lockout, it means there is a problem somewhere. A lockout is a safety feature that only happens if the boiler has identified an issue with a component or something wrong in the system.

The problem is working out what that problem might be and how to fix it. There are lots of issues that can result in a lockout.

In this short guide, we will highlight the main ones and tell you how to fix them. We will also explain how you can figure out exactly why your boiler is in lockout and what to do about it.


Explaining boiler lockouts

If you are new to all this, you might well be wondering what exactly a boiler lockout is. The answer is quite simple; it is a failsafe mechanism designed to protect your boiler and you if there is a suggestion of a problem with certain key aspects of the boilers functions.

Boiler lockouts can be caused by all sorts of things including:

  • High pressure
  • Low pressure
  • Low/No fuel
  • System blockages
  • Power issues
  • Failing components

The lockout is essentially intended to stop the boiler working. This helps to prevent issues from becoming dangerous and should rule out the risk of boiler explosions, fires, and long term damage to components.

How to identify a boiler lockout

The most obvious distinguishing factor of a boiler lockout is that you will find you have no hot water or central heating in your home.

If you take a look at the boiler itself, you are likely to see a flashing light someone on the display panel. This is usually red or green but this will depend on the make and model of boiler you have.

If you have a newer boiler, your display panel is also likely to be showing a fault code. This will be a combination of letters and numbers that isn’t usually displayed and is the boiler’s way of telling you what the problem is.

What to do if your boiler is displaying a fault code

If you have a fault code showing on your boiler display panel, you will need to figure out what it means. There are a few ways to do this:

  • Check your boiler manual – this will usually list all possible fault codes and explain what they mean.
  • Check the internet – Your boiler manufacturers website should also have a list of fault codes and their causes.
  • Call your boiler manufacturers customer support line – If you can’t find details of your code anywhere else, call your boiler manufacturers customer support line. They will be able to explain what is causing the problem.

Once you know what is causing the problem, you can then figure out what is the best way to fix the issue. A lot of people will try resetting their boiler and then carrying on as normal. This might work for a short time, but the problem will almost certainly reoccur and is not a long-term solution.

The best thing to do is to find a solution that will solve the underlying cause of the fault.

Common causes of boiler lockouts

Every boiler is different is every boiler problem could be caused by a variety of things. But there are some common issues that we see occurring again and again which will usually lead to a boiler lockout. These are:

  • Pump issues

Central heating pumps can easily develop faults, blow seals, or become blocked and seize up. If the pump in your boiler isn’t working properly, a boiler lockout is likely to be the result.

  • High/Low water pressure

Your boiler should be operating at a pressure of around 1.3 bar (check your manual for the precise details for your boiler). If this pressure goes up too much or drops too low, your boiler is likely to lockout as a precaution.

  • Ignition problems

If the ignition on your boiler fails three times, it is highly likely that it will be programmed to lockout.

  • System blockage

It is quite easy for boilers to become blocked with sludge or other debris from your heating system. Equally, the condensation pipe that vents outside can also freeze or become otherwise blocked. If your boiler detects this, it is likely to lockout.

  • Heat Exchanger Blockage

The heat exchanger can get blocked up with limescale. This will usually result in your boiler making a whistling noise. It is likely to result in temperatures within the boiler rising too high and thus triggering a boiler lockout.

  • No Power

A power failure can be caused by a faulty display board, a blown fuse, tripped electrics or a more serious problem with your boilers printed circuit board. Whatever the cause, it will almost certainly cause your boiler to lockout.

  • Fan issues

The fan inside your boiler is critical for venting potentially toxic gases outside your home through the flue. If the fan isn’t working properly, your boiler could become dangerous so a failsafe will kick in and your boiler will most likely lockout.

Resetting your boiler

If you have a fairly modern boiler, it is likely to have a reset button or function. This will usually be located somewhere on the display board and require you to press or hold down the button for a few seconds in order to force your boiler to reset.

Older boilers will have a reset function but you will need to consult your boiler manual to find out what process is required.

Simply resetting your boiler after it has gone into lockout will not solve the underlying problem, so it is advisable to identify the issue and resolve it before resetting. If the problem is a major one, it is likely that the boiler will lockout again quickly in any case.

Resolving the underlying problem

There are a few basic checks you can run on your boiler to see if you are able to resolve the problem that is causing it to lockout yourself. Anyone can try these things, but if you are in any doubt, it is advisable to get a qualified gas engineer to come and check over your boiler for you:

  • Check the pump is working

When your boiler is reset, open the casing and place your hand on the pump. If you can feel small vibrations and hear a humming noise, that indicates that the pump motor is working. If the pump feels hot, it could be blocked. Try tapping it gently to see if you can release the blockage.

  • Check the power

Check that the fuse on your boiler isn’t blown. If it is, plug the boiler in elsewhere or replace the fuse. Also, check that your main fuse box hasn’t tripped too. If it has, reset the switch, then reset your boiler again.

  • Adjust the pressure

If the pressure on your boiler is too high or too low, try adjusting it appropriately to see if this resolves the problem.

  • Check the Printed Circuit Board

If the printed circuit board isn’t working, it is likely that no power is getting to your boiler. You will be able to tell because nothing will be displayed on the display panel.

You will need a gas engineer to check out this issue and it is likely you will need a replacement, which could prove expensive.

  • Monitor the heat flow

Your boiler will have a flow and return pipe underneath it. One should be extremely hot and the other slightly cooler as this water has been around your heating system.

If the return pipe is very cold, this suggests there is a blockage somewhere in your system that is slowing down the flow of water. This will need a heating engineer to come round and flush your system to clear any blockage.

How to solve regular lockouts

If lockouts are a common problem and as soon as you solve one problem, your boiler is finding another, it is likely that your boiler is reaching the end of its life. The best option when things get to this point is to buy a brand new boiler.

When doing this, you will save yourself money on repair bills and also probably on utility bills too since modern boilers are far more energy-efficient than older ones. If you get a long warranty, your boiler will also be covered for any faults that emerge for the next few years.

It is always advisable to get a variety of quotes and we would advise one place to go for a quote is WARMZILLA.

WARMZILLA is an online boiler installation service that offers fantastic boilers from all the top manufacturers at the lowest possible prices. Fill in their quick online form (no personal details required) for a fixed-price quote on the best boilers for your property.

They have some great special deals such as extended 10-year warranties available too.


Boiler lockouts are a safeguarding mechanism that stops your boiler from becoming dangerous or getting badly damaged.

A lockout can be caused by all sorts of different things and it is advisable to identify and fix the underlying problem rather than just reset the system.

In this guide, we have identified some of the most common causes of lockouts. We have also suggested a few tips on how to fix these problems and recommended you try WARMZILLA if lockouts become a common problem and you need a new boiler.

Have you had problems with boiler lockouts? What was causing the issues in your system? Did you manage to fix the problem or did you end up buying a new boiler? Do you have any questions or problems that we haven’t addressed in this guide?

It is always helpful to hear the experiences and questions of readers, so please do share yours with us using the comment box below.

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