Heating off but radiators hot

herman2811

Does anyone have any suggestions please:

We obviously have our heating off at the moment, but every time the boilers kicks in to heat our water, we are finding that our radiators get hot as well. This only seems to happen for a few minutes, but does happen every time the boiler is active.

Turning each radiator off has "fixed" the issue for the moment, but for example, in the autumn/winter we would want to leave the radiators on and wouldn't want this to happen every time the boiler kicks in.

A google search indicated there may be a valve that is sticking/faulty, but I can't find any such valve.

Our set up is that we have a boiler in the kitchen, a thermostat downstairs to control the whole system, and a hot water storage tank in the upstairs bathroom which also has a timer on it. Both the downstairs thermostat and storage tank timer are currently set to off.

Any help/advice would be much appreciated - I don't really want to pay someone a call-out charge if I can help it!

sickparrot

Yeah the diverter valve could be stuck open, usually due to black sludge in the system. Diverter valve repair kits are usually available for any specific boiler but it's usually a fairly big job stripping one down, cleaning it out and fitting the new parts. It's do-able (I've done a few) but only if you're reasonably confident and have a bit of general plumbing experience.

Crinkmeister

Can you feel the pipes on each affected radiator and tell if the return pipe is hotter than the flow on any of them? If so, you have a common problem caused by poor pipework layout. If flow is hotter than return on every affected rad - ie as it should be - then you have a control valve fault.

What boiler model is it?

herman2811

sickparrot wrote: »

Yeah the diverter valve could be stuck open, usually due to black sludge in the system. Diverter valve repair kits are usually available for any specific boiler but it's usually a fairly big job stripping one down, cleaning it out and fitting the new parts. It's do-able (I've done a few) but only if you're reasonably confident and have a bit of general plumbing experience.

Where would this diverter valve be?

Crinkmeister wrote: »

Can you feel the pipes on each affected radiator and tell if the return pipe is hotter than the flow on any of them? If so, you have a common problem caused by poor pipework layout. If flow is hotter than return on every affected rad - ie as it should be - then you have a control valve fault.

What boiler model is it?

Doubt it's a layout problem, as I haven't seen the issue before, and our house is about 12 years old.

Off the top of my head, I think the boiler is a Potterton Suprema 40L.

2013yearofthehouse

We had this problem last year (our system is about 40 years old though). We needed a new 3 way motorised valve - it looks a bit like this: http://www.gwsupplies.co.uk/p7228/drayton-central-heating-motorised-valve-3-port-ma1-679-3-22mm.htm ours is in the upstairs airing cupboard, where the hot water tank is (boiler used to be in there too, but it was moved to the kitchen years ago).

sickparrot

herman2811 wrote: »

Where would this diverter valve be?

Sorry I just had a look at the manual it doesn't look like there is one, or I can't find it anyway without reading every page. There's a heat exchanger though so ??? dunno, it looks like everything is external to the boiler unit. I've only had experience with combis where everything is in the same box.

zaax

The diverter valve is stuck an easy, DIY fix. But it might be worth getting the whole system serviced, and / or pay monthly fee to the likes of British gas - £16 is not bad for a boiler service and piece of mind

Gloomendoom

There may not be a diverter valve if the system is gravity hot water and pumped heating.

southcoastrgi

Gloomendoom wrote: »

There may not be a diverter valve if the system is gravity hot water and pumped heating.

which it won't be if it's only 12 yrs old

mid postion valve fault would be my guess

herman2811

zaax wrote: »

The diverter valve is stuck an easy, DIY fix. But it might be worth getting the whole system serviced, and / or pay monthly fee to the likes of British gas - £16 is not bad for a boiler service and piece of mind

southcoastrgi wrote: »

which it won't be if it's only 12 yrs old

mid postion valve fault would be my guess

Where are these valves likely to be? I can't find anything - are they likely to be enclosed within the boiler or storage tank?

southcoastrgi

it won't be inside the boiler, it will look something like this, normally quite close to the pump