This is most likely a frost protection feature or it could just be a fault but its not all combi boilers that do it & if it is a frost protection you should be able to disable it 

I think it might be a fault as I remember I noticed this happening with my parents’ gas boiler a few summers ago, firing up for no reason. Maybe needs checking with your friendly boiler engineer? I think a switch of some sort was replaced??

Hi all - thanks for your ideas.

I phoned Worcester/Bosch, boosted by your suggestions.

He said if you don’t press the eco button after you have switched the boiler back on,

it stays by default in pre-heat mode, and keeps the boiler (heat exchanger?)

at 54C no less, so when you take hot water it arrives at the tap a bit faster.

So you’re burning gas 24/7 to avoid those precious painful extra seconds

of waiting for your hot water to arrive!

And that’s not the opt-in setting, it’s the default!

I’ll check the eco setting stops this happening, and count those extra seconds

for your informed decision-making.

Hoping all boilers that do this can be undone,

and everybody who has one doing it realises it and solves it as easily.

As for the regular silt-avoiding pump stints, the man said it’s not good

for them not to take place, but you can’t stop punters switching their boiler off.

Cheers!

Wow, that seems very wasteful ! and yes, a bad idea as a default. I suppose it’s an example of how we got used to cheap gas so burning a bit more just to make life comfortable.

Last summer was the first time I turned off my pilot light when I realised how much it was burning, even though the heating wasn’t on for 3 months  I’d let it burn every summer for years !!!

Thanks - so how much was your pilot light burning?

I would say about 4kWh per day.

Wow I would say that sounds too much, but if you’re down to zero

without the pilot that’s it! Again how wasteful manufacturers are

when nobody knows about it.