What are the signs of a boiler overheating?
The most common signs that your boiler is overheating include:
- A boiler shutdown / cutting out is the most important and obvious sign that there is an overheating issue with your boiler.
- Radiators are cold at bottom (indicating a blockage in system)
- Boiler displaying an error code on the digital display (typical on modern boilers) - this sign must be dealt with quickly to prevent any extensive damage or danger.
Why do boilers overheat?
A common reason why boilers overheat and cut out is when hot water that needs to be sent to the cylinder, taps or central heating system is not circulating effectively. Normally, this is due to a failing pump or blockage in the system such as a build-up of limescale. Additionally, there may be a thermistor issue causing this overheating.
What can cause a boiler overheating and cutting out?
Most often, the cause of an overheating boiler is safety features failing. Modern boilers are designed to cut out when the system detects signs that the boiler temperature is too high to prevent serious damage. Typically, the unit will display an error code and will identify (on the digital display) what is wrong.
Is it dangerous when boiler temperature is too high?
A boiler temperature being too high isn’t always a huge cause for concern or a safety threat, but it must be dealt with promptly to prevent any extensive damage.
However, with overheating there is a small risk that an explosion may occur or indeed components within the unit melting and releasing toxic smoke. If you have a modern boiler, this is much less of a concern as the unit will typically lockout before becoming dangerously hot.
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How to fix an overheating boiler
To prevent serious damage and eliminate any risk of explosion, seek a gas safe engineer for unit repair.
If the reason your boiler is overheating is limescale build-up somewhere in the system, your central heating system may just need a chemical flush to eradicate the blockage and get things running smoothly again. This build-up is often called ‘kettling’ as it sometimes sounds like a whistling kettle.
If the issue is on an even smaller scale and the blockage is minor, your radiators may just need bleeding.
You can also detect if this is the problem, by checking your radiators to see if they're colder at the bottom than the top.
If a failing pump is your diagnosis, you will need a heating engineer to either repair or replace the pump depending on the extent of this damage. A thermistor issue will also require the assistance of a professional.
How to prevent your boiler temperature getting too high
To stop overheating from occurring; you need to start with prevention and good central heating system maintenance. Having an annual boiler service will give you peace of mind that the model is working well and reduce chances of an unforeseen expensive repair.
If your boiler is more than a decade old, it is seriously worth considering a replacement. As aforementioned, newer boilers are a much safer and smarter appliance. They can detect issues earlier and lockout before the unit explodes. Buying the right boiler can sometimes be overwhelming, consulting our new boiler guide will help you find the best model for your household with ease.