central heating is staying on even when the boiler (heating and hot water) are turned off

[SarahR71]

Has anyone ever had this problem and solved it? My central heating is staying on even when the boiler (heating and hot water) are turned off. I had to open the windows last night the house was so hot… It happened last year when the weather got really cold but then started working properly again. Any ideas? Thanks

A quick Google suggests it could be the anti gravity valve.

Mine does this when the batteries in the wireless thermostat need changing!

Turn it off completely and restart when needed?

This happens with ours sometimes as the PP said it is when a valve remains in the open position. We resolve ours by turning the boiler off at the mains, leaving it for an hour and then turning back on. If that doesn’t work you will need to call out an engineer.

It happened here when the thermostats lost WiFi connection with the control box. But the heating wasn't on permanently. I think the default setting is that it comes on at certain intervals. Maybe something like that?

I had leakage from hot water side to heating side once, had to change a valve, but if both are off it can't be that. I assume no electrical immersion (back up) heater in the hot water cylinder?

As below ours was the diverter valve too, an easy DIY thing to do, no plumbing, but you need to have the hot water on for that to accidentally heat the radiators by that means.

Diverter valve maybe. We had to get ours replaced

I've had this happen twice. It is 100% the motorised valve which is jammed.

You need to locate it, (ours is near our hot water tank in airing cupboard) there will be a toggle switch there which you should move back and forwards. That may fix it or you may need a new motorised valve. We have had two in 25 years here.

It's a little box about 3inches square attached to a pipe.

p.s. We have a Nest thermostat and it would show as all heating/hotwater off, but the radiators would be boiling hot.

Not sure how the rads can be hot if the boiler is actually turned off? What have I missed?

It's the thermostat, not the boiler off. Ours would show 9degrees (we don't have central heating on at night) but the radiators would be boiling.

The motorised valve was jammed in 'on' position

Knackered thermostat, or dead battery in thermostat

Battery in thermostat check that first. Then if not it’ll be the diverter valve (was with a gas engineer for 10 years, I’ve picked up a few tricks) 😂