Why does my boiler keep turning on by itself?

Question

My combi boiler seems to fire up on its own at random points through the day even when no hot water or heating is running. Is this a fault or is it normal?

Daniel · Answer

Hi Peter, with Combi boilers there is a function called preheat that can be selected on or off and will be found in the users instructions of the manual. 
Typically this function would be selected to be on where there is a hot drawer off point on the system it’s of a long distance from the boiler.
So the boiler is coming on periodically during the day to heat up a small amount of hot water so that it is ready to be drawn off making waiting times at the Tap sooner to arrive. 
Personally, I would see this as a waste of energy and turn this function off if you can allow the time for it to get to that tap or us a different tap closer to the boiler for hot water. 
It is also possible that there would be a shorter route to this Tap from the Boiler. 
Hope this is helpful.
Kindest regards, Daniel Frost at Frost Heating and Plumbing.

Daniel · Answer

It's probably a pre heat function, most combi boilers have, it reduces the wait time for hot water to reach your taps you'll probably notice it more in the summer months as your heating won't be on. On most models of boilers it can be turned off and is usually nothing to worry about

Abdurrahman · Answer

This can actually be normal in many cases, especially with modern combi boilers, as they may fire up on their own due to features like the pre-heat function (to keep hot water ready), frost protection, system checks, or pump overrun.

Phil · Answer

It’s a fault most likely your controller is faulty change the batteries if you have a wireless thermostat and reset make sure the green lite is on

Why does my boiler keep turning on by itself?

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