Water only, some rads piping hot

I had a similar problem a few years ago which took three British Gas engineers to work out, It turned out to be a small neoprene valve buried deep inside the boiler that had coroded and was allowing a bit of "feedback" into the CH system.

Relatively new boiler (Dec 04) but can ask BG to look at that option.

Just checking around again and it might - repeat "might"! - be that the main bathroom radiator's return pipe is warmer than I'd have expected (it's almost completely covered by a box so not easy to grasp). If that's where the hot water is entering the heating loop then I still can't see why the other rads appear to be warming via the feed pipe.

I accept that my knowledge of CH is substantially lower than many of the posters, so apologies if this all sounds stuoid!

john_n snipped-for-privacy@yahoo.com wrote:

Do you have any evidence to substantiate your statement that the 3-port valve is working fine? This is often the culprit in cases like this - although this would usually result in *all* radiators getting hot - not just those upstairs.

Yes, it seems to be OK....reasons for such confidence are:

- No real heat flow along the pipe that feeds the rads, just a small bit of conduction

- Like you say all the rads would proabbly heat up

- And the man from BG tested it - with me watching!

Roger Mills wrote:

If its leaky rather than jammed open, you tend to get a trickle of hot into the rad system, and then gravity feed does the rest.

I had similar in my old installation..one or two rads would get warm to hot under HW. Since one was the bathroom one, I never bothered to fix it.

It's gotta be right then, if BG tested it!

If the valve *is* ok, it suggests that there's some sort of reverse - or one pipe - circulation going on.

Looks like a floor-boards-up job, to identify exactly where all the pipes go and thus to find where it's been plumbed wrongly.

and less hassle!

Thanks, j