Mystery radiator - help!

[frenziedmonkey]

One of my radiators isn't following the same rules the others are sticking to: it's permanently cold. I've bled it a couple of times but there's no trapped air - cold water runs out, despite all other radiators being hot.

The only change to the system has been the addition of a new radiator in the loft; this was fitted to existing pipework that had been run up there for that purpose a year before, with the radiator itself being fitted about two months back.

All radiators worked after the new pipework was put in and as far as I'm aware even if the new radiator was fitted the wrong way round, that shouldn't affect just one downstairs.

It's hard to say whether the problem arrived at the same time as I've only recently put the heating on.

What am I missing folks?

 

[footprints]

Has it got a thermostatic valve? They often stick over the summer.

 

[frenziedmonkey]

It has... I've turned it on full and couldn't feel any resistance suggesting the internal valve was jammed.

 

[Gasguru]

No, take the thermostatic head off and check the pin underneath on the valve is free to move up and down.

 

[footprints]

Take the head off turn off all other rads and chances are it will pop up.
If not a couple of sharp taps on the side of the valve should free it

 

[frenziedmonkey]

Ok thanks both, I'll give that a go. Cheers for the advice.

 

[footprints]

Just to be clear run the system with the head removed and other rads off and also run it while tapping, just a sharp tap with a screwdriver head or the handle of an adjustable spanner no big hammers

 

[Gasguru]

That's gonna depend which way the water flows through the valve. Gentle taps on the pin often does the trick.

 

[DIYTom]

You can sometimes get a serious airlock that ordinary bleeding doesn't clear. What my plumber showed me to do was to (with the system running) turn both radiator valves all the way off, then remove one of the bleeding valves. With a bucket to catch the water slowly turn one of the valves back on. If there is an airlock there'll be a lot of clunking and the sputtering water before it runs free. Shut the valve back down, then try the other one to make sure. Finally put the bleeder back in, then open both valves and you're sorted.

 

[frenziedmonkey]

Well the good news is that the radiator fills when the head's off, good call folks.

The moment I put the head back on though we're back where we started. I can see that the core of the head is sprung and it's quite stiff so presumably it's just holding the pin down once in place, regardless of the setting. I'll try a new one, see where we go from there.

Thanks again