Is your boiler getting super hot? If so, there's certain things you'll want to check over in order to cool it down.
An overheating boiler is something to address as soon as possible.
In the worst-case scenarios, an overheating boiler runs the risk of exploding, which needless to say could result in injuries or worse.
So, what are the signs to look out for that your boiler is overheating?
Moreover, what causes this and how can it be fixed?
Let’s take a look!
Boiler old, unreliable and costing a fortune in repairs? Simply answer these questions, get your fixed price and you could get a new one installed as quick as tomorrow.
Why Do Boilers Overheat?
First and foremost, modern boilers come with safety features which should trigger a boiler lockout before your boiler can overheat.
When this happens an error code will usually appear along with the boiler lockout.
In some cases, this error code will correctly tell you what the cause of the lockout is, whereas it’s also possible that as the boiler nears overheating, the boiler triggers a lockout, but the incorrect error code comes up on display.
However, these safety features can fail. In most cases, when a boiler overheats it's because the built-in safety features have failed to do their job.
An overheating boiler can be dangerous for several reasons:
Boiler components may melt which could cause toxic smoke to be released and this could prove dangerous for inhabitants on the property and nearby.
In rare cases, an overheating boiler might literally explode leading to injuries or/and deaths. Thankfully this is very unlikely but the fact it’s possible is enough reason to take an overheating boiler seriously, along with the risk of toxic smoke.
Having your boiler serviced once a year could be key to preventing any of these risks in the first place.
But you are probably here because you are concerned about a potential overheating boiler.
Signs of an Overheating Boiler
What will happen when a boiler overheats will vary from model to model.
With that said, more than likely your boiler will lock out by itself upon overheating or when it nears overheating.
However, if the boiler hasn’t shut down but you see an error code or some other alert on the boiler, go to the manufacturer’s manual and check what this code/alert means.
It may also mean your boiler is overheating or at risk of overheating.
What to Do If I Think My Boiler Is Overheating?
If this happens you should turn the water off. You can do this by turning off the inside stop valve.
This is usually found beneath the kitchen sink, but you may also find it under the stairs, beside the front door or elsewhere.
You can check your water provider’s manual or give them a call if in doubt.
If your boiler is overheating and experiencing a safety failure, water running into the boiler could cause the boiler to explode.
This is because steam accumulating inside your boiler will increase its pressure more and more.
Once you’ve turned off the water, call a heating engineer. If you can, call them on their emergency contact.
However, if you are worried that your boiler may explode, get out of the property and call emergency services.
Overheating Boiler Common Causes
Again, once you’ve turned off the water, you shouldn’t wait around trying to diagnose the issue.
You should contact a heating engineer (ideally on their emergency contact) or if you are worried for your safety, you should call the emergency services.
Therefore, the causes and fixes discussed in this section are just to give you an idea of what might be going on.
However, any of these potential fixes must be undertaken by a qualified heating engineer since an overheating boiler or even a potentially overheating boiler must be dealt with promptly.
You may be interested in Gas Engineer Allen Hart explaining the most common boiler problems and how you can resolve them in the video below:
How to Fix the F1 Fault
Accumulation of limescale
Firstly, it’s possible that your heat exchanger has suffered from a build-up of limescale.
The heat exchange serves the purpose of heating up relatively cool water prior to circulating it through your property’s radiators.
Aside from increasing the danger of your boiler overheating, the accumulation of limescale in general can lower the lifespan of your boiler.
Limescale accumulation in a boiler is also called kettling since it can result in noises which sound like a whistling kettle.
How to deal with limescale build-up
The accumulation of limescale in a boiler can be fixed through power flushing.
While this can usually be done DIY, if there are concerns that your boiler is overheating or may overheat, a heating engineer will do this for you after diagnosing the issue.
This is important because the issue should be fixed there and then, and the heating engineer will need to verify that power flushing 100% fixes the problem.
System Blockage
Strange noises coming from your heating system or/and your radiators failing to heat up as usual generally suggest there’s a blockage of some kind.
A blockage may come in the form of an air blockage or physical blockage.
How to deal with a system blockage
Your radiators may be suffering from air blockages which means they need to be bled.
Alternatively, limescale, rust, and other debris may have built up in your heating system, meaning that hot water cannot circulate correctly.
This can be fixed by power flushing. Again, these must be dealt with by a professional even if they are often DIY-friendly tasks.
Lastly, your boiler may have a frozen condensate pipe. This could happen especially during cold times of the year.
Again, a professional must fix this in relation to an overheating boiler, even if in most cases it would be okay to fix DIY.
An issue with the Thermistor
Your boiler’s thermistor is designed to inform the printed circuit board or PCB whether it needs to bring the temperature up or down based on demand.
The PCB, by the way, is basically the control centre of a boiler.
If the thermistor malfunctions this could result in the water temperature going too high leading to an overheating boiler.
How to fix a broken or faulty thermistor
A qualified heating engineer must fix or replace the thermistor and adjust any other issues found in the boiler or general heating system.
An issue with the Pressure Release Valves
These valves as you can tell are designed to release pressure.
They do so as the boilers get hotter, thus if the pressure release valves stop working it can cause a boiler to overheat.
Some pressure-release valves (depending on the design and brand) are known for suffering leaks.
How to fix a faulty pressure release valve
A heating engineer should inspect them if this is believed to be the issue.
It’s critical that the heating engineer avoids removing the seal to deal with the leak, otherwise, the boiler could overheat more, and the risk of an explosion would increase further.
They will either repair or replace the pressure-release valves.
Pump Fault
Another potential cause of an overheating boiler is a fault with the pump.
A boiler’s pump is used to circulate water throughout a central heating system.
If the pump experiences a fault, hot water will be stuck in the boiler which may cause overheating.
How to deal with a pump fault
A heating engineer may be able to fix the pump but, in most cases, it will have to be replaced.
Cost of Fixing an Overheating Boiler
The overall price of having a boiler fixed that is overheating or may overheat will depend on the nature of the repairs or replacement jobs.
This will consist of both the price of labour and supply costs.
As for the price of labour, heating engineers usually charge between £30 and £60 per hour, however, this would depend on factors such as where in the UK you are based.
This is because labour prices differ from region to region. If you hire a heating engineer in an emergency, you will pay more.
Estimated costs for a repair or replacement job:
Power flushing a heating system
£400 to £500Bleeding radiators
£75 to £150Thawing a frozen condensate pipe
£30 to £120Repairing or replacing a thermistor
£55 to £160Fixing or replacing pressure release valves
£35 to £135Repairing a boiler pump
£30 to £120Replacing a boiler pump
£180 to £300Brand new boiler installation
£800 to £2,800 *
*You may want to replace an entire boiler if your boiler is pretty much beyond economical repair. If it is old and the repair/replacement work required is quite expensive (e.g., replacing a boiler pump), it may be more financially sensible to have your boiler replaced.
This may not apply to power flushing, however, as this would generally apply to the entire heating system.
Either way, if your boiler is particularly old and becoming prone to issues, it may be time to have a new boiler fitted.
Obviously, many households may not have this option right now, at least not in the context of paying for a new boiler upfront.
However, depending on your credit history, you may be able to purchase a boiler on finance.
In other words, you might be able to buy a boiler now and pay for it later. In most cases, you’d have to pay interest, albeit interest-free options do exist.
Get a Quote for a New Boiler Today
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