Potterton Profile central heating problems

RHYSDAD

Hi there, apologies if this is the wrong area to post this so please feel free to move if need be.

Basically, if there are any knowledgeable central heating experts who might be able to help, we have a problem with our central heating system. We have a Potterton Profile boiler (not sure of exact model) and all was fine up until last year when it seemed to be that the hot water and heating started working independently. What i mean is that we have to have the heating on for a bit, then the water on for a bit, they won't work together. Now i know there is a valve which switches back and forth but i can't think what it's called. Someone told me that's probably the problem. Now, putting some towels away today in the airing cupboard i noticed this silver box and noticed it had a little lever on top:

http://www.flickr.com/photos/48369322@N02/5216973249/sizes/m/




What does this do? Is it meant to be locked in place or does it switch back and forth? When i had a twiddle of it, it was very stiff and wouldn't lock back into the recess you can see but then it did and also it seemed to move back on it's own! Ghostly!! I think i seemed to have both the hot water and heating working together at one point, the water tank on first, then the radiators were getting hot too but when i turned the thermostat down on the hot water tank the boiler just clicked off and therefore so did the heating. When you slide the control off for the water and back on again for the heating, the boiler clicked in. It almost seems that it needs that trigger to set the boiler going again. Is this control valve knackered or am i as clear as mud?!? Any help appreciated if you can fathom what the hell i'm on about.......

macman

It's a motorised valve that is supposed to move on it's own responding to demand for hot water in your tank from the tank 'stat. If it's sticking then you won't get consistent hot water.
If you turn the tank 'stat down then that cuts the DHW demand and so the boiler will shut down, unless the CH side is calling for heat. It could just be sticking, but may need the head gear or the valve replacing. Either way, you should get it sorted, as it's a simple enough job for a plumber to fix (or to DIY).
Put the tank 'stat back up to a minimum of 60C (or as hot as you want your hot water) and then work the lever a few times, it may just be sticking and need freeing up.

Pincher

Access is an issue here.

It seems to be right in the middle of a worktop!

I had a service contract years ago, and that valve failed.
Access was tight, but no fixtures had to be removed.
The engineer made a report, and my service contract could not be renewed, unless the valve was moved!

macman

I think it's just some battens forming a support shelf for clothes drying in the airing cupboard. If so it should be very easy to remove a couple if more access is required.

lozzaman

Definitely sounds like the motorised valve and not the boiler.
Our 3 way valve was sticking all the time - so I took the head off (not the whole valve) and managed to wiggle it free. You do not need to drain the system for this. It has been trouble free for 4 years since.

gas4you

How many pipes does the valve have on it. 2 or 3?

You can only remove/replace the valve head only if there is a raised 'dimple' on the top surface of the valve at one end.