Cold Radiator - A real puzzler

Ebe_Scrooge

I know there have been lots of threads on here about cold radiators, and I know all the common causes. But this one has got me stumped.

One radiator is permanently cold. It's an upstairs one if that makes any difference. So far, I've :

Checked that both the lockshield and TRV are fully open.
Checked that the pin on the TRV is operating correctly.
Bled the radiator - all of them, in fact.
Turned off every other rad in the house, left this one fully open, turned heating up to full whack.
Taken off the rad, flushed it through with a hose ( it was clean anyway, as it turned out ).
Before I replaced the rad, I opened the lockshield and the TRV valves one at a time, just to check, sure enough water came blasting out of each one. So no blockages in the pipes leading to or from the rad.
When I refitted the rad and re-opened the valves, it filled up rapidly, so no issues with water flow. The water it filled up with was warm ( as the heating had been on so the rest of the system was warm ).
But then that radiator soon cooled down, and now, weeks later it still doesn't heat up when the heating's on.

I'm stumped as to what the problem could be.

The only other thing to mention, the house is pretty new, only four years old, and this radiator hasn't worked since we moved in. The previous owners were in the forces and rarely at home, when we asked them they said they never used the heating in that room anyway.

So it's *possible* that it's never worked from new. But even so, I can't think what the problem might be. Any bright ideas ?

DVardysShadow

If it has never worked, I would say it is probably plumbed in from flow to flow rather than flow to return.

Ebe_Scrooge

I hadn't thought of that ! Thanks, that's a great idea - looks like it's time to get floorboard-lifting

anotherbaldrick

Could still be that cartridge in the thermo valve has stuck or failed.
Drain the radiator , shut the lockshield valve on the rad return fully , open up the thermo valve fully and also the air vent snifter, then see if the rad fills . If you get no filling or hiss of air the valve is stuck shut, a blow from a heavy hammer might shift it but take it a bit easy.

anotherbaldrick

DVardysShadow wrote: »

If it has never worked, I would say it is probably plumbed in from flow to flow rather than flow to return.

Perhaps if system is flow and return ring main circuit. If rads are on separate runs from manifolds no.

roger196

Some of the older TRV can only be fitted on the flow side. Modern ones are bi-directional. Might be worth checking if other suggestions have not solved the problem. Would be interested in what actually solves this.

Ebe_Scrooge

roger196 wrote: »

Would be interested in what actually solves this.

Thanks for all the helpful suggestions. Having tried all of them, at the weekend I took the bull by the horns and lifted the carpet and floorboards. Sure enough, both sides of the radiator running into the return, nothing into the flow. After much cursing and swearing, managed to re-route the pipework, everything is now working perfectly.

I shouldn't be surprised, really, by all accounts the plumbers that got the contract for our estate were a right bunch of cowboys, loads of our neighbours have had problems of some sort with their plumbing. Apparently the owner of the plumbing company played a lot of golf with the boss of the house-building company .......