Does Your Boiler Fire Up, Then Turn Off? Here’s Why

Are you tired of going back and forth with your boiler as it keeps switching off? Well if your boiler seems to have a mind of its own, it’s probably because it has broken down or become defective. The good news is, that every broken thing can be fixed, and so can your boiler. Here is a guide that will help you get through any boiler issues right from the comfort of your home.

Now there are quite a few potential causes that might be interfering with your boiler system’s functionality. Although some severe issues may need to call for professional help by gas-safe registered engineers, there are few which you may be able to rectify yourself at home. For instance, the “Pre-heat” function in a Combi boiler is a common reason it turns off, which is perfectly normal and does not need assistance.

On the other hand, a reason to scrutinise and carefully look into can be short cycling. To get to the root of the problem and understand why your boiler is acting up, take a look at some of the common reasons this happens.

What is Boiler Short Cycling?

First, we need to understand the basic structure of a boiler. Within your boiler, there is a small reservoir of heated water, which comes into use when hot water is required on demand. After some time when this water begins to cool down, the internal thermostat detects the temperature and reheats the water. Once it is done, the boiler will switch off.

Now, this cycle of reheating keeps repeats whenever the water cools down. The higher the frequency of reheats, the more fuel, and electricity your boiler uses, which eventually burns the heat exchanger out. Cracked heat exchange is every boiler owner’s nightmare as it burns a hole in the pocket and also contributes to carbon emissions.

Coming back to Short-Cycling, if you have an oversized boiler, it will consume more energy, in turn producing more steam than it can condense. This causes short-cycling. A heating engineer will often advise on using oversized boilers due to their high efficiency. The latest Combi boilers on the other hand are 90% efficient which obviates the need for an oversized boiler.

Possible reasons For Combi Boiler Short-Cycling

Let us take a brief and informed look at what causes Short-Cycling.

Valve Issue

If your temperature control valve defects then the water temperature in your boiler will not be regulated. As a result, the water temperature might hike up and hence turn the boiler off to protect it from overheating and getting damaged.

At times the valves present underneath the valve get blocked which blocks the water flow through the boiler. You can prevent this by keeping an eye on the valves underneath. If you don’t notice any problem, then the issue could be with the valve inside the boiler, which can be fixed only by a professional.

Water Pressure

The pressure gauge located in front of your boiler will help keep you track of the water pressure. The steady-state is set at 1.5 bar and if the needle deflects to the extreme left or right, then it a clear red flag. Low pressure can lead to a leak which will turn the boiler off. This leak may originate from a pipe joint, radiator, or from underneath the boiler.

Whatever the genesis is, once fixed, your boiler will return to its healthy state. Another reasonable explanation behind your boiler flaking out on you could be the air trapped. You could try bleeding your radiators to recover from it.

Heat Exchanger

The life expectancy of a heat exchanger is no more than 7 years. If your exchanger has worn out or is damaged, then replacing it is the obvious choice. However, keep in mind that heat exchangers are costly and might not be worth investing in if your boiler is old and burnt out. We would recommend you to buy a new boiler with a registered trademark instead of giving the original one for repair.


A thermostat is used to observe the external temperature of the boiler and if the temperature drops down to a certain point, then it turns itself on. Now that you know what a thermostat does it’s easy to guess that if your thermostat is faulty then it will not monitor the temperature accurately and cause the boiler to shut down.

If your thermostat is old then you should consider investing in a wireless or smart thermostat. This is more economical in the long run as it will cut down your heating bill. A few smart thermostats like Google Nest adjust the temperature by sensing your movement and learning your schedule. This is highly beneficial in terms of money and is more sustainable as well.

Water Pump

A pump is one of the key parts of a boiler system as it regulates the temperature inside the boiler. A damaged water pump will not circulate water around the boiler system which will lead to overheating or worse boiler fires. Thus to prevent further damage, the boiler turns off. This is your cue to get in touch with a gas engineer, who will help you find a new water pump and work this problem out for you.

Fuel Supply

Fuel supply is the first and foremost component required to get your boiler going. If there is a hindrance to the fuel supply, the gas boiler will not function. The first step to knowing whether your fuel supply is compromised is checking the source of it. If something is interjecting it then it will hinder your boiler functionality. Make sure you contact your energy supplier if you’re facing issues with your fuel supply.

Frozen Condensate

Frozen Condensate is a common complaint during winter months when the condensate in pipes gets frozen. In simple terms, a condensate pipe is a drainage pipe used to discard acidic water out from your boiler. If the temperature around this condensate pipe low then this acidic water can freeze. A frozen pipe will block the water flow and as the boiler keeps sending more water, the ice barrier will send it back to the boiler. To fend off the damage, the boiler locks itself and displays an error.

Another way to figure out whether your pipe is blocked is when the boiler makes a gurgling noise as a result of the blockage. You can reverse this blockage by using warm water to free the ice and resetting the boiler.

Frequently Asked Questions

Is it normal for a boiler to turn on and off?

The question depends on how severe the reason behind this fluctuation is. To find out you must first understand why it keeps turning off. For instance, if the issue is with the condensed pipe or an underneath valve, then you can easily resolve the issue right there. On the other hand, if it is the faulty heat exchanger causing the intervention, then it is best you give it for repair or replace it. When dealing with a heating system fault, you need to call a gas safe registered engineer for help.

While there is a myriad of reasons why the boiler could switch on and off which shouldn’t be worried about, you must keep a check on your boiler frequently. Maintaining a boiler is an easy task and if done consistently then it will save you a lot of damage and money in the long run.

What is boiler Short-Cycling?

Boiler short-cycling is when your boiler stops its work to avoid any damage and maintain the central heating system. When the central heating is lopsided, the boiler stops all its work as overheating may cause boiler fires and damaged parts such as the valve, water pump, and internal wiring. Even a tiny fault in the system could cause a Short-Cycling. To prevent this impairment, boilers switch off.

Make sure that you keep your boiler in check as it may lead to permanent damage if not taken care of. Even if it is a small repair that needs to be kept in check, make sure you call gas engineers to solve the issue and guide you for further assistance instead of jumping on to buy a new boiler.

When is the right time to call a gas safe registered engineer?

In short, if your gas boiler is creating havoc and continuously switching off and on, then you need to get in touch with gas boiler engineers. They will free you of the headache and find the fault and fix it immediately. However some issues can be mended at home, so carefully read through the guide above and you will find the answer to your boiler misery in no time.

There are many engineers out there that will come to your rescue when in need, but you must start small and at home to keep your boiler healthy and in one piece. A wise piece of advice would be to keep your boiler system regularly in check to steer clear of any boiler fires and keep the central heating system in its best condition.

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