Boiler heating radiators - when not on?

[3sixty]

Good morning all. Firstly I apologise for my non-technical descriptions.

My boiler had a service after I found it to be dripping (not too much of a leak, but enough to make me worried) and the engineer said it needed a new PRV and seals.

I bought them, had them fitted and it has since stopped leaking/dripping down. However, now with the boiler turned off (as its summer), the radiators are getting hot when I use any of the hot water from the taps. It feels like the radiators are on full blast when the shower is on. After a while, the radiators cool as I presume there is not any more flow of hot water getting to them.

Does anyone have any ideas why? It sounds like some of the hot water meant to be going to the taps/showers is being passed round to the 'radiator loop' (technical term ).

Edited by 3sixty on Tuesday 2nd June 08:47

[anonymous-user]

IIRC this is normal, ourscertainly does it & always has.

[Muzzer]

My heating comes 'on' when the hot water is on.

I thought there was something wrong - the thermostat is down to 10 degrees and the heating itself is off. But when the hot water cuts in, the radiators get warm.

Dashed annoying in the summer when it's baking hot anyway.

[3sixty]

I dont remember it doing this before... but its highly annoying going for a shower, then coming to sleep and finding the bedroom is being heated by the radiators.....

[Deva Link]

What is described in the OP is most certainly not normal.

I assume (based on the reference to the shower) that it's a combi boiler? If so then the hot water diverter valve isn't working properly (or at all).

[anonymous-user]

Ours did this, had BG out to fit new divereter valve and still does it. I was told pressure relief??

[3sixty]

That confuses it even more.. as I've had pressure relief valve (the PRV i mention in OP) replaced.

[anonymous-user]

Sorry, i was told the valve will heat the radiators if there is too much pressure. The PRV usually opens and lets water out from an overflow i think??

[Fume troll]

Deva Link said:

What is described in the OP is most certainly not normal.

I assume (based on the reference to the shower) that it's a combi boiler? If so then the hot water diverter valve isn't working properly (or at all).

+1. 3 port valve or its control system has failed.

Cheers,

FT.

[B17NNS]

Sounds like a problem with the diverter valve.

[Ferg]

Most combination boilers will dump heat down the heating circuit when you CLOSE the tap, but it shouldn't be noticeable in the rads...

I'd supect the diverter in the boiler.