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Understanding The Different Causes of Overheating Boilers

Understanding The Different Causes of Overheating Boilers


For any household, a constantly overheating boiler can lead to some serious problems. That said, it’s important that you can address the situation right away. Boiler problems can be caused by a few reasons, ranging from hardware failure to buildups.

If you find that your boiler has been overheating, check to see whether your model has the built-in safety feature that shuts off the boiler once it reaches a critical temperature. This prevents long-term hardware damage caused by the frequent overheating, or worse, an explosion if enough pressure has built up inside the boiler.

Signs of an Overheating Boiler

Diagnosing a boiler might be tricky for people who aren’t familiar with these kinds of hardware. Generally, if a boiler is overheating you will notice that it will shut down frequently. This is a modern safety feature that prevents pressure buildups. If this happens, the first thing you should do is to turn off the water supply. This reduces the risk of overpressure even further by cutting the boiler’s supply of water.

Afterward, it is best to contact a professional who is familiar with boilers. This is the surest way for you to get an accurate diagnosis of your equipment unless you have experience dealing with modern home boilers.

Causes of an Overheating Boiler

As we mentioned before, an overheating boiler can be caused by a variety of reasons. Because of this, it might take you some time to figure out how to fix the problem—of course, having a professional check out your boiler can certainly speed things up.


A common problem that affects older boilers is blockages. These can be caused by sediments in your water supply. When these happen, the pipes going throughout your boiler are restricted, making it harder for your boiler to function efficiently.

Thermistor Breakage

Boilers will make use of devices called thermistors to monitor the temperature of the water. A failure in a boiler’s thermistor can lead the appliance to develop problems with heating the water, either causing the boiler to heat too much or too little.

In either case, this prevents your boiler from running efficiently and potentially causing it to overheat. To diagnose this kind of failure, a professional will need to assess the thermistor themselves to see if a replacement is in order.

Build up of Limescale

Most water supplies have no control over the limescale buildup caused over years of use. This can happen with any appliance. Boilers will be more likely to experience these more often though due to how they operate.

If limescale has indeed built up inside your boiler, what happens is that it prevents the heat exchanger from doing its job efficiently while also restricting water flow inside the boiler. Combined, these two symptoms can cause serious overheating boiler problems in your property.

Appliance Failure

Of course, there is always a chance that the appliance you received was faulty from the start. There is nothing you can do in these situations except to call for a professional to assess the unit. If they do find a fault in the manufacturing, you would be able to get a refund for your overheating boiler.


We hope this article proves to be useful when it comes to helping you gain a better understanding of why your boilers overheat. Now that you are aware, be sure to keep everything you’ve learned here in mind so that you can keep your boilers in good working condition.

If you’re in need of boiler repair services, then you’ve come to the right place. We here at Bay Area Mechanical specialize in maintenance contract work for commercial and industrial facilities, which includes the servicing, repair, and installation of boilers. For more information on what we can do for you, visit our website today!

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