Boiler Ignition Lockout – Causes & How to Fix

Last updated: November 15, 2023

Often a boiler lockout occurs at the worst possible time, often during running the kids baths or in the depths of winter.

Either way the root cause of why a boiler doesn’t ignite would need to be investigated in order to get the boiler back up and running again.

This guide will cover the most common faults that can occur causing a boiler ignition lockout and provide some troubleshooting steps, where safe to aid getting the boiler re-lit.

As with any boiler issue, if there are ever any doubts in relation to the cause of the issue or your confidence to investigate, always call a qualified heating engineer for assistance.

See local Energy Guide approved installers we recommend for your job:

Wondering which boiler manufacturers performed best? Check out our best boiler brands guide for the full rundown and if you are trying to determine who the best boiler installation company is, check out our Warmzilla and Boxt reviews.

What is a Boiler Lockout?

Firstly, let’s discuss what exactly is a boiler lockout.

A boiler lockout is the term used to describe when a boiler shuts down due to a fault. The lockout process is a safety mechanism designed to protect the boiler, it’s internal components and the household from further damage or even danger.

In the first instance following a boiler lockout, the property owner or tenant can try to re-set the boiler following the manufacturer’s instructions to see if the boiler itself or time passing has resolved the matter.

Always remember to give the boiler plenty of time when resetting to allow the internal parts and processes to restart fully.

If following the initial reset, the boiler does not reignite, the fault could still be at play and therefore further investigation will be required.

Most boilers will display an error code following a boiler lockout, self-diagnosing the cause.

The error codes can be found in the boiler’s user manual or by searching the make and model of the boiler online.

Need a new boiler and interested to know which boiler brand is best? Check out our best boiler brand guide, as well as the best combi boiler models currently available. 

How to Fix a Boiler Ignition Lockout: Common Reasons

There are a number of common reasons of why a boiler can fault and lock out.

Below we discuss the most common faults that often result in a boiler lockout:

#1 Faulty Boiler Pump

The pump inside the boiler can develop a fault for a number of reasons including; debris causing a blockage, a leak starting or a blown seal.

See local Energy Guide approved installers we recommend for your job:

If the error code displayed on the boiler signals a heat pump fault, a Gas Safe registered heating engineer will be required to safely assess the condition of the pump and advise on the next steps.

Did you know the efficiency of your boiler can impact the amount of energy it uses and ultimately impact your heating bill costs? Check out our guide to the best condensing boilers if you are interested to find out more. 

You may also find our review of the best eco-friendly boilers of interest.

#2 High or Low Water Pressure

Boilers have an optimum water pressure level in order to function properly. The setting for your specific make and model of boiler can be found within the manual.

Should the pressure be too low or too high, the boiler will lockout to protect the internal parts from damage.

Should the pressure be too low, the pressure filling taps can be utilised to adjust the pressure. For further guidance on how to use the pressure filling taps, consult the boiler manual.

Should the pressure be too high, bleeding the radiators can help in the first instance. There are videos of how to undertake this available online if you are unsure.

Got a common boiler problem? Check out our quick fix guide on boiler lockout, boiler ignition faults, boiler PCB faults, faulty diverter valves and boiler timer issues.

#3 No Electric Supply

A simple fault can be the loss of power either through a local outage or via a tripped switch within the property.

#4 System Blockage

Other reasons that a boiler lockout can occur is due to system blockages either because of debris within the boiler itself or within the system, or often in the winter months, a frozen pipe.

Unless the cause is an obvious frozen pipe (which can be defrosted manually), a professional heating engineer will be required to safely investigate the cause.

Sometimes blocked parts can be cleaned or other times there is damage caused by the debris and therefore the parts need replacing.

#5 Ignition issues

Most boilers will attempt to ignite three times before locking out for safety purposes. If the boiler does not ignite, the cause could be due to a fault within the electrode and ignition lead.

In this scenario a Gas Safety registered heating engineer will need to be called out to test the electrode and ignition lead and replace if necessary.

Considering a new boiler and wondering what size boiler you need? Or are you wondering which boiler installation company is best?  

#6 Faulty Boiler Fan

There is a fan built inside the boiler that pushes out the emissions and gases that the boiler produces, into the boiler flue and then disperses them into the atmosphere.

Should a boiler detect that its fan is not working correctly it will shut down for safety purposes.

This cause may be noticed by the homeowner or tenant as often the fan inside the boiler would normally make a slight noise when in operation.

If this cannot be heard, a faulty fan may be the reason behind the boiler not starting and therefore a specialised heating engineer will need to be called out to confirm the diagnosis and investigate fixing the fan.

See local Energy Guide approved installers we recommend for your job:

Usually, a replacement fan is an expensive part to source, so if the professional heating engineer advises that a new fan is needed, depending on the age and condition of the boiler itself, may mean that a new boiler is a more cost-effective option.

What size boiler is right for your home? If you are thinking about a combi boiler, it is largely determined by the number of radiators in your home.

Check out our complete guide to new boiler installation here if you are wondering about the best type of boiler for your home. 

How much may a new boiler cost? Are you considering converting from a conventional to a combi boiler? Use our boiler installation cost calculator to get an estimation.

#7 No Pilot Light

Inside a fully operational boiler, the pilot light should be lit, however should the internal electrode and ignition lead develop a fault and stop working the pilot light may go out and not re-light.

In this scenario a specialised heating engineer will need to be called to investigate the cause and advise the most appropriate next steps.

The above are the most common issues however there could be other issues at play such as a gas or carbon monoxide leak.

Gas leaks may be detected by regional suppliers, an error code on the boiler or by a household member due to the distinctive smell, whereas carbon monoxide is odourless and therefore detectors should be installed.

Either leak can be very dangerous and must be treated as an emergency by leaving the property immediately and calling the necessary authorities.

In addition to gas leaks, there may be, on the rare occasion a gas outage resulting in no gas supply to the property.

If this could be the case check if other gas appliances have a supply or check with neighbours to see if there is a local issue. If so, keep up to date with details of the outage by checking the appropriate regional supplier’s website.

The following are issues that can cause a boiler to lockout are rather straightforward although can easily be forgotten:

  • Thermostat setting– The thermostat controls the temperature that the boiler will activate upon (if programmed to be running) and will heat the property to. If the thermostat is set too low, the boiler will not start up.
  • Check the timer clock and programme – As briefly mentioned above, a boiler often has a programme set up controlling when the boiler should operate. If the boiler clock or the programme is incorrect, the boiler will not turn on.
  • Prepayment meter – If the boiler has a prepayment meter associated with it, the homeowner or tenant should check that the meter has a credit balance applied to enable the heating system to work.

How to Fix a Boiler Ignition Lockout Next Steps

We have covered a wide range of boiler ignition issues within this guide, however if the basic troubleshooting hints included do not resolve the ignition problem you are facing, always seek the advice of a qualified heating engineer for further support.

Depending on the cause of the ignition issue, the cost to fix the boiler will vary. Some causes may require labour only for clearing blockages for example whereas other issues could require expensive replacement parts.

If the latter, discuss the option of replacing the boiler with your heating engineer.