Boiler turns on briefly throughout the night

Question

We moved house a few months ago and our property either has the same or a very similar boiler to our old house. It's a condensing boiler, a Worcester Greenstar 37cdi and the controls look identical. However, it has an odd behaviour that our old one didn't: it turns itself on, very briefly, at intervals through the night.

Nothing actually comes on. The fire-up only lasts maybe twenty seconds and the radiators don't heat up. It's the middle of summer so the thermostat is turned right down. I think - but I'm not certain - that it does this at fairly consistent times.

The trouble is that where the boiler is positioned underneath two of the bedrooms it sometimes wakes people up with the noise. We'd really like to stop it, especially since the fact our old boiler didn't do it suggests it's some kind of setting.

However, I can't figure out what it might be. Trying to troubleshoot it on google isn't helpful as you get a lot of answers from people whose boilers are coming on full blast during the night, which isn't our problem at all.

Does anyone have any suggestions as to what this might be or what I could try to change to stop it from happening, short of turning the boiler off all night every night?

Answer 1

The boiler has a couple of functions that might explain this:

Preheat keeps a supply of hot water in the boiler at all times. It reduces waiting time when used for hot water supply. The manual explains how to turn that on and off. This could be the cause, even if you're not using it for hot water. Heat loss would cause a cycle of regular heating as you've observed.

Antifrost senses and fights near freezing temps in the boiler. Less likely but if wired incorrectly or if the antifrost sensor is bad this could be the cause.