Hot radiators upstairs when hot water is on

[LukeB]

Hi All, I have the following problem heating works okay but when I turn off the rads upstairs stay on if the hot water is on, from reading other posts it sounds like I might have a 3-way valve problem, but I cannot find a 3-way valve on my system, the only motorised valve I can find is on a pipe coming from the bottom of the hot water cylinder but this valve is a straight on/off valve with one pipe in and one pipe out!
The system is a typical system with a header tank in the loft an old Potterton boiler downstairs and a hot water tank on the 1st floor.

Any ideas would be greatfully recieved?

 

[kevplumb]

View media item 11148
is this a new prob

has anything been altered / changed

 

[StephenW]

I guess your boiler has one set of big pipes which go to and from the hot water cylinder and one set which goes to and from the radiators. If you look at the pipes from the boiler which feed the radiators, somewhere on the vertical run you might find a "gravity valve". Not sure what they're actually called but they are about the same size as a normal isolator valve. The idea is that a spring loaded valve inside closes off to stop the hot water rising up the pipe and so heating the upstairs radiators. When using the central heating and the pump comes on then the pressure is sufficient to hold this valve open and let the water through.
It could be that this valve has failed. Mine used to make a knocking sound and was not working as it should so I replaced it with a manual valve which I turn off during the summer.

 

[LukeB]

Kevplumb, its a new prob as far as i'm aware, moved in to the house in March this year we used the heating a few times then and didn't notice the same problem, the only thing that has changed since then is that 2 rads have been off and now back on again, 1 upstairs 1 downstairs.
The motorised valve I can see looks simaler to the one you have shown but it is a Sunvic.

StephenW, yep I can see the sets of pipes but nothing that looks like a valve at all.

Anymore ideas?

PS the boiler is a Potterton Kingfisher 2

 

[StephenW]

Same boiler as mine!

Just to make sure I haven't confused you, here's a link to site with a picture of what to look for. It's still my guess that it's your problem but then again I'm only an interested amateur!
http://www.gasman.fsbusiness.co.uk/gravity_hot_water_pumped_heating.htm

 

[LukeB]

Thanks for the pics, least I know what to look for!
I have looked again but def. can't see one of these valves.

 

[LukeB]

Okay I have a C-plan system but def not a Anti gravity valve on the flow out from the boiler to the upstairs rads, I am planning to fit one myself, hope this works, any thoughts anyone?