Cold radiator

[llykstw]

I had a new radiator installed yesterday in the bathroom - it's a Hampton towel rail radiator, see here - http://www.plumbworld.co.uk/0-2438

It replaced an old towel rail that was going a bit rusty and was past its best. Because the new rad was a slightly different size from the last one, there was a little bit of pipe work needed to connect it in, so I got a plumber round to get the pipes connected.

Having refilled the system, there are no leaks (thank God) but the new radiator doesn't heat up properly. All the other radiators are fine, including one on the next floor above the bathroom, and heat up uniformly. The new radiator, however, only heats up across the bottom, and up the left hand side (above the TRV-controlled inlet). If you were to draw a diagonal line across the radiator, from the top-left (above the TRV) to the bottom right (above the lockshield), then only the bottom-left side heats up. The towel rail doesn't heat up at all.

The bleed valve is on the top-right of the radiator (on the towel rail itself), i.e. on the part of the radiator that remains cold. If you open the bleed valve then water comes out, so it doesn't look like there's any trapped air in there.

Does anyone have any idea why half a radiator won't heat up, in the absence of any apparent airlock at the top? The thing did take a knock in transit, and there are a couple of very small dents in one side (the right hand side), but I can't see how a knock can cause this sort of problem.[/url]

 

[MANDATE]

I think I would first ensure the lockshield valve is fully open. Next I would remove the head of the thermostatic valve, there should be a steel pin protruding, which is part of a spring loaded valve. With the head removed you should be able to depress the pin (but you will need to place something hard between thumb and pin coin), because it should be in the fully open position.
Once your happy that it's open try the heating again without the head being fitted.
With respect to the thermostatic head there are usually plastic stops that can be set to limit the movement and stop the valve being set on max.
If it's a new radiator it can't be sediment and if air is bled off it can only leave one of the valves in my opinion. ( apart from the damage)
I would have thought though that bleeding the radiator would make it hot near the bleed valve.
Is it possible the thermostatic valve could be fitted incorrectly. ie against the flow or on the return side. sorry I can't be more helpful.