Boiler not firing up for central heating

Boiler breakdowns or boilers not firing up, always occur at the most inconvenient time! Any amount of downtime can be problematic, and it will be an urgent concern to get the heating system back up and running again.

There could be a number of reasons why a boiler won’t fire up. Throughout this article, we will provide some troubleshooting suggestions for boilers that are not firing up.

Boiler Not Firing Up: Simple Checks

There are a handful of common reasons why boilers do not fire up. To eliminate some basic issues, work through the following list:

  • Thermostat setting is too low – During times when a boiler is scheduled to be running but isn’t firing up the thermostat setting could be the issue. If the room temperature where the thermostat is located is warmer than the setting, the boiler will not turn on.
  • Timer not activated – If the boiler has a time programme, the reason the boiler is not turning on maybe as simple as it’s outside of the time program. However, another reason that the timer may stop the boiler turning on is if the timer unit itself has lost power or has been reset following a power cut for example.
  • A tripped fuse – Sometimes following a power cut or power surge, the fuse will trip for safety purposes. It is always worth checking the fuse box during these troubleshooting steps to eliminate this issue.
  • Prepayment meter – Should a prepayment meter be in situ; it would be worth checking that the meter has credit applied to enable the system to work.
  • No gas supply – It would be worthwhile checking if the gas supply coming into the property, either by attempting to turn on other gas appliances, such as a cooker, or asking of neighbours are having issues. If there is a local issue, contact the emergency gas service.

Should none of the above be able to solve the issue with your boiler not starting, the next step is to try a boiler reset. To do this, refer to the boiler’s manufacturer instructions.

After a reset has been completed if the boiler doesn’t restart, there could be a more serious issue that will require investigation.   The following are common issues that could be the next concerns to investigate.

If you need to reset your boiler too often, it may be a sign of a more significant fault, such as a faulty PCB, a boiler leak or a central heating pump problem, and if your boiler isn’t igniting, it may be time to consider getting a new boiler quote.

Boiler Pressure issues

A boilers pressure will naturally vary when in use as heating water causes expansion which increases the pressure within the boiler.  A healthy, happy boiler will typically have a pressure of between 1 and 2 bars of pressure. Luckily most boilers feature pressure gauges to enable easy identification of the pressure levels inside the unit.

If the pressure is too low the boiler will usually shut down whereas the consequences of high pressure inside the boiler are that the pressure release valve, or PRV, will release the excess water.  If this doesn’t happen the internal parts will fail.

With a boiler pressure issue, there are steps that can be taken yourself to adjust the pressure on the system.  The pressure can be adjusted by the use of the taps, which are usually located underneath the boiler, however, always check with the boiler’s manufacturer manual the source of the taps and the process to make pressure adjustments.

If pressure issues are an ongoing concern in ageing boiler wear and tear on the internal parts may be taking place.  In this case seek the advice of a specialist engineer to review the boiler and advise if there are any improvements that can be made, or if it’s time for a replacement.


Airlocks can cause system performance issues with inconsistent heating with only parts of radiators getting warm or noisy pipework.  In this case, the first step is to bleed the radiators when the system is off and cool.

A bleed key will be required to loosen the nut at the end of a radiator, as well as a container to collect any water that is released when bleeding the radiators.  If you are unsure how to bleed radiators, try looking up a video on how to bleed radiators before you start.

Frozen condensate pipe

During the colder months, a common issue with boilers is frozen pipes.  This issue is particularly frequent with condensate pipes which drain wastewater away from the boiler to an external drain.

Boilers often have a safety mechanism built in to prevent the boiler from starting if it recognises that pipes are frozen.  Should the system pipes freeze, the quickest way to get back up and running is by applying heat sources to the area such as storage heaters to thaw them out.

Burner blockages

Sometimes a non-starting boiler can occur due to internal debris blocking the burner.  In this scenario, a specialised engineer will be required to clean the burner or replace it if damage has been identified.

The pilot light has gone out

Pilot lights are essential for boilers to function, however similar to the burner, the jet that a pilot light comes out from can become clogged with debris.  An engineer is also required in this case to either clean the pilot light jet or replace it if needed.

Is your boiler losing power? Or is your boiler pressure too high? If your boiler is old, past its warranty, it may be time for a new boiler replacement.

Boiler error codes

Thankfully most boilers feature a display window showing the current boilers pressure bar reading and if there are issues, error messages will also be shown. Error messages can take the guesswork out of identifying the problem with the boiler.

Error messages are specific to the manufacturer and therefore it would be worth checking the manufacturer’s website to identify what the error code refers to.

Boiler not firing up the summary

There are a number of reasons that can result in a boiler not firing up.  Some basic issues can be checked yourself using the troubleshooting tips provided in this article, however, if there is any doubt regarding dragonising the concern or confidence to undertake the check, always call a qualified heating engineer.

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