How to Tell If a Boiler is Overheating

Professional plumber checking a boiler control panel

There are many faults that can affect how well a boiler works, several of which may also cause overheating. If you think that your boiler might be overheating, there are a few ways to check what the issue might be.

In this article, we’ll explain more about what happens when a boiler overheats to enable you to identify an overheating boiler at home.

We’ll discuss the main causes of an overheating boiler and give you some tips and advice on what you should do if your boiler is overheating.

What Are the Signs of Boiler Overheating?

There are a few telltale signs of an overheating boiler. If your boiler keeps cutting out or turning itself off at unusual times, then excess heat could well be the problem.

In some cases, boilers will not switch off if they have overheated. Modern boilers will display an overheating error code, making the task of identifying the problem that bit easier.

Boiler Overheating Causes

Boilers can overheat for a number of different reasons. Some of the most common causes of overheating are listed below.

Remember, in almost all cases, these faults can be avoided with regular servicing and maintenance. Looking after your heating system is key.


In the vast majority of cases, a buildup of limescale is to blame for an overheating boiler. That’s because limescale accumulates in pipework and in the heat exchanger itself. This causes the water inside to get too hot and, therefore, the boiler to overheat.


Over years of use, pipework can become rusty, and that rust can soon start to cause problems within the heating system. As rust and other debris build up, blockages will start to form.

These blockages tend to result in rising pressure in the system. When paired with a problem in the pressure relief valve, this inevitably results in overheating.

A Pump Fault

The pump is responsible for pushing water through the heating system, taking hot water where it needs to go to keep radiators warm.

But when the pump is affected by a fault, water won’t be moved as it should, and hot water can continue to be heated far beyond desired temperatures.

Thermistor Fault

Heating systems use what’s known as a thermistor to measure the temperature of the water and communicate with the boiler so that water is always heated to the correct temperature in the most efficient way possible.

When this part fails, it can easily result in overheating, as this vital communication ceases to work as it should.

How to Stop Your Boiler Overheating

Overheating is a problem that can often be easily remedied. It’s just a case of identifying the cause of excess heat in the system and working on that particular fault.

Take a look at some of the most effective ways of stopping an overheating boiler below.

Get An Engineer to Perform a Powerflush

Using plenty of pressure, a powerflush can rid a heating system of the damaging limescale and other debris that causes overheating. A qualified engineer will be able to advise you on whether a power flush would solve your problem.

Check the Condensate Pipe

If it’s a blocked condensate pipe causing your boiler to overheat, you may be able to remove the blockage by warming the pipe.

This will defrost any ice that has become stuck, allowing the condensate pipe to work properly again.

Replace the Pump

A faulty pump will usually require a replacement, and a qualified engineer will be able to do this for you.

Pumps can often be replaced with minimal disruption, so if it’s a problematic pump that’s causing your boiler to overheat, your engineer will complete this boiler repair for you.

Use a Scale Reducer

If your heating system is becoming damaged by limescale, it’s possible to combat the buildup of harmful limescale by installing a scale inhibitor. Speak to your engineer about whether a scale reducer would lengthen the lifespan of your boiler.

Get Advice on Boiler Overheating Problems

If you’re struggling with a boiler that keeps overheating, just give our team a call. We can assist with anything and everything to do with overheating, from helping you with how to tell if a boiler is overheating to solving all kinds of boiler overheating problems.

Contact our team to find out more about the signs of boiler overheating and what you can do to get your boiler back in full working order.

Give us a call, and we’ll soon have your heating and hot water working as they should.

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