Heating not on, one radiator is

[Saucery]

We have a combi boiler (no hot water tank). The heating is on a timer but all the little switches are down, have been for weeks.
The bathroom radiator is happily pumping out heat.
Is it a poltergeist or something more horrific like an expensive boiler repair visit?

diverter valve in boiler is worn out.

While waiting for the repair to be scheduled, turn the radiator off. No use to use great force, just turn the knob down finger-tight.

If you don't have TRVs, you may find the next nearest rad rgen warms up. Turn it off. If you have TRVs, just turn them to about 3.

except

some superior installations have the bathroom radiator heated differently so you can always warm or dry towels on it.

This is unusual with a combi, but not impossible.

How weird! I've been meaning to start a thread about this for ages. Thanks PJ and OP.

Thank you so much, PigletJohn. No exorcism needed then
It definitely isn't a superior installation. We are not sure when it started doing it tbh but certainly not set up to work that way and hasn't always done it. Will book a non urgent call from our boiler maintenance people.

Hope you get yours sorted too, JigglyTuff.

PigletJohn, do you mean that it's possible to heat a towel rail from the boiler when the rest of the central heating is off? I thought I'd have to resort to having them converted to duel fuel to achieve that.

it's very easy if you have a hot-water cylinder nearby. Superior installations often have a towel rail or radiator that is heated whenever the cylinder is heated, which is typically during and after a bath or shower, so, the best time. Add a TRV to prevent overheating the bathroom in hot weather.

Otherwise, it can be done by zoning, which will be more expensive, but easy enough if it is included in the initial design and installation. More tiresome if you have to pull up floors and lay new pipes.

Otherwise, it can be done by zoning, which will be more expensive, but easy enough if it is included in the initial design and installation. More tiresome if you have to pull up floors and lay new pipes.

PigletJohn, you're a genius! I can see why you're so highly regarded around here.