Why is my boiler not firing up?

3 October 2023

Having a boiler that refuses to fire up can be quite frustrating, especially during the cold winter months when you really need it. Various factors can contribute to this problem, ranging from simple user error to more complex technical issues. 

In this article, we’ll explore some common reasons why your boiler may not be firing up and provide some troubleshooting tips to help you out.

It’s worth noting that modern boilers come with a whole host of electronic and physical sensors, valves and switches that are designed to shut the boiler down before something serious happens. 

These faults are usually accompanied by an error message on the readout, if it has one – it’ll be something like F1, E3 or similar. Your manual will have a page or two dedicated to decoding these messages. 

That might mean it’s something you can fix yourself (e.g. low or high pressure), or it could be a sign that you need to call out a plumber specialising in boilers.

In some cases, there could be a problem that the sensors are unable to detect, in which case the boiler will simply stop working without an error code. If this happens, it’s a good idea to turn it off so that pumps aren’t running, and get in touch with a heating engineer. 

If there’s a visible leak, turn off the boiler’s water supply if you know where it is. You shouldn’t turn the gas off unless you can smell gas, and even then, you should prioritise opening windows, getting out of the house and calling the gas emergency number on 0800 111 999.

So, if your boiler isn’t working, it could be for one of the following reasons.

The thermostat is set too low

Before diving into more complicated solutions, ensure that your thermostat is set to the correct temperature and is in the heating mode. If it’s set to something like 15 degrees, the boiler will probably never fire up because the house may well be at that temperature naturally. It may sound obvious, but sometimes even the simplest mistakes can cause headaches. 

If you have a wireless thermostat, check the low battery indicator – you may simply need to replace them. 

Insufficient Gas Supply

A common reason for a boiler’s failure to ignite is an inadequate gas supply. Check if your gas supply has been interrupted, if not there could be a fault with the gas valve. 

A quick way to check is to make sure all other gas appliances in your home are working correctly – that can help identify if the issue is isolated to your boiler or more widespread. If you have no other gas appliances, ask a neighbour if theirs is interrupted. If so, call your gas supplier.

Pilot light problems

Older boilers, particularly those with a pilot light, may experience issues with ignition. If your boiler has a pilot light, check to see if it has gone out. 

If so, follow the manufacturer’s instructions for relighting it. Remember to follow safety precautions and avoid any gas leaks. If you are unsure or uncomfortable working with gas, it’s best to call a professional heating engineer to assist you. 

Faulty ignition system

Note that most modern boilers don’t have a pilot light – they spark up electronically. If your boiler has an electronic ignition system, a faulty igniter or control module might be the culprit. In this case, there’s nothing you can do – call a professional engineer to diagnose and repair the issue. Attempting to fix the ignition system yourself could further damage the boiler or pose a safety risk.

Pressure loss

Some boilers have a pressure gauge that indicates if the system’s pressure is too low. If the pressure is below the recommended level, your boiler may switch itself off when it’s on, or not fire up at all. 

You can check the pressure gauge, typically located on the front or underneath the boiler, and consult your boiler’s manual or manufacturer’s instructions on how to adjust or top up the pressure. It’s likely that your pressure readout will be on a digital display rather than a pointer-style gauge. You might need to cycle through a few settings to reach it – consult your manual. 

Blocked condensate pipe

Modern condensing boilers have a condensate pipe, which removes waste water and condensation from the boiler. If this pipe becomes blocked or frozen, your boiler won’t fire up for safety reasons. Inspect the condensate pipe for any obstructions or signs of freezing. If you find a blockage, try thawing it gently using warm water or a hot water bottle. 

If freezing condense pipes are an issue for you please let us know as we can install Condensate Pro which is brilliant to resolve this issue.

Electrical issues

Sometimes, a boiler may not fire up due to electrical problems. In the absence of power, your display and any lights will probably be dead. 

Ensure that the boiler’s fuse or circuit breaker hasn’t tripped and reset it if necessary. If the issue persists, it is advisable to contact a qualified electrician or boiler specialist to examine the electrical connections and identify any faults. 

Age and Wear and Tear

Boilers, like any mechanical equipment, have a limited lifespan. If your boiler is quite old or has been experiencing frequent breakdowns, it may be time to consider a replacement. A professional heating engineer can assess the condition of your boiler and provide recommendations based on its age and functionality.

As you can see, if your boiler is not firing up, there can be various reasons behind it. Start by checking simple things like the thermostat settings, gas supply and pilot light (if you have one). Ensure the pressure is correct and inspect for blockages or frozen pipes.

If these troubleshooting tips don’t resolve the issue, it’s best to contact a professional heating engineer or specialist plumber. Remember that working with gas and electrical systems can be dangerous, so it’s better to seek expert assistance to avoid any risks or further damage.

Stay warm, and let’s hope your boiler is in proper working order for a comfortable winter season!