Immersion heater/boiler HELP please

[DCmum95]

Hello!
we have recently moved to a house with an immersion boiler system (very old).

we have just noticed that our upstairs radiators are coming on when we put the hot water on.
we don’t have the heating on at all but we have the hot water on twice a day, for 1 hour in morning then 1 hour in evening. We have noticed that the upstairs radiators are red hot!

google says it could be a faulty diverter valve.

is anyone knowledgable on this stuff by any chance??

we are so clueless and also skint so dreading the cost of a plumber

This used to happen with my also very old system. My gas engineer did explain why it happens, can't quite remember now but it is to do with it being a gravity fed system.

Just turn the upstairs radiators off for the summer and that should sort it?

BTW diverter valves are usually only in combination boilers, not the set up you have.

I have a diverter valve in my system boiler set up.

Oh, sorry. I thought they were only in combis! Shows how much I know.

You might find this thread useful OP (though it does get a bit technical)It does seem to be an issue with older systems.

https://www.diynot.com/diy/threads/gravity-hot-water-heats-upstairs-rads-when-on.525835/

Yes could be a sticking zone valve. I had this once when the radiators were blasting out heat even thought they should have been off.
You can take the motorized head off the valve, spray on some WD40 and waggle it gently with a pair of pliers to free it up.
There are probably videos on YouTube about it.

It was a faulty diverter valve that caused our heaters to heat when the thermostat was turned down low. We also have a system boiler with hot water cylinder.

Did you have a plumber/gas engineer to come and fix it - if so how much did it cost if you don’t mind me asking x

Some really helpful messages here, thank you!!

We have boiler cover with British gas so they fixed it for us

If you you have a combi or system boiler, it will have a diverter valve inside it.

If you have a conventional boiler, it will (probably) have a 3-port valve next to the boiler or next to the HW cylinder. There are a few very old designs that rely on gravity convection to the cylinder, but most have been updated or replaced. Old or large systems may have 28mm pipes which are more expensive than the usual 22mm

It is cheaper and easier to change the separate one because you don't have to take the boiler apart or pay for a boiler-branded part.

Look for something resembling one of these. Honeywell and Drayton are the most usual. There are also cheap brands. They usually last ten to twenty years.
www.screwfix.com/search?search=Port+valve+