Why does my boiler fire up randomly?

A boiler is the heart of any home, keeping you warm on cold nights and providing those relaxing, hot baths when you just need some downtime. When your boiler has a problem, it can be a cause for concern. Some boilers can switch on and off and have a mind of their own. Has your boiler been firing up randomly? If so, continue reading our helpful guide to discover what could be causing your boiler to misfire and solutions you can try.

Preheating combi boiler

If you have a combi boiler, you may have noticed that it turns itself on and off intermittently, especially during the winter. Combi boilers do this from time to time as a ‘preheat’ function, heating up water to a required temperature so there’s some ready for when the taps are switched on.

To confirm whether or not this is a feature of your boiler, check the owner’s manual.

However, if your boiler is turning on and off quite regularly – around six times per hour for example – this is an indication that something is not right with the system. You should not attempt to fix this yourself. Instead, with the use of Boiler Cover from toasti, you can hire a qualified professional to examine the boiler and take care of the repair.

Short cycling

In some cases, your boiler could be doing something known as ‘short cycling’. This refers to the cycle switching itself on and off to prevent overheating when the heat it generates cannot disperse quickly enough.

This is a common problem when a powerful boiler has been installed which generates heat at a faster rate than can be dispersed by your hot water or central heating system.

There are other causes behind short cycling, though, and they are:

  • Undersized pipes
  • Pump issues
  • Oversized boiler
  • Radiator sludge
  • Poor system design

High water pressure

Another possible cause for why your boiler is firing up randomly could be high water pressure. When the water pressure in your central heating system is too high, it can cause damage to components and force the boiler to shut down.

Once the water pressure has dropped, the boiler will fire up again and restart the preheat process. And if the water pressure gets too high again, the boiler will shut off.

If you suspect that high water pressure is the problem behind your boiler’s intermittent switching between on and off, try bleeding your radiators to lower the water pressure.

Faulty PCB

Another issue that could be causing your boiler to randomly fire up is a faulty printed circuit board (PCB). The PCB is the heart of your boiler and is in charge of the operation of all the different components to ensure that they’re all working correctly.

If there’s a fault with the PCB, it could fail to recognise the timer settings and result in the boiler switching on despite the timer settings saying otherwise.

A faulty PCB is a problem that only a qualified professional should deal with. Booking a yearly boiler service can help to detect these types of problems early, resulting in an easier fix.

Location of central heating thermostat

The central heating thermostat acts as an on/off switch for the heating system in your home. When the thermostat detects internal temperatures below your settings, it instructs the boiler to switch the central heating on to warm your home. Once the temperature has risen above a set value, the thermostat will then instruct the boiler to switch off.

In some cases, the thermostat could be located in an area of the house that could lead to unnatural readings. Draughty places like next to the front or back door, a fan or washing machine can all lead to the thermostat thinking it’s cooler than it actually is. A breeze through a door could directly affect the thermostat’s readings, leading it to believe that the home’s internal temperature is much lower than it actually is, resulting in the boiler being switched on and off.

To prevent this issue, consider moving the thermostat to the living room or deep into your hallway to provide more accurate readings.

Boiler services from toasti

At toasti, we boast a boiler and heating team of expert boiler engineers to provide top quality service for all our customers.

We specialise in new boiler installations, repair and services for customers across North Yorkshire, Birmingham, Manchester, Merseyside and more. To ensure we consistently deliver a high-quality service, toasti only uses Gas Safe Registered engineers who are highly qualified and extremely trustworthy.

If you require any assistance with your boiler, or would like to get a quote for a new one, contact us today on 0161 527 7326, or email us at info@toasti.co.uk.