Radiators hot at one end and cold at the other.

BruceK · Mar 23, 2019

Hello. I need a bit of advice please about getting heat through to 2 radiators. All the others are piping hot but these 2, in adjacent rooms (bedroom & en-suite) are piping hot right the way up at one end and stone cold at the top at the other end. There's a hot band for the bottom third of the radiators along their length and plenty of heat leaving the radiators at the outlet valve. I've bled them but no more air comes out (obvious really because the top is hot at one end). I've tested them for level/horizontally and they're okay. I've also tried running the Grundfos pump at different speeds (you can hear water rushing through when valves are almost closed so there's plenty of pressure) and finally I've tried different settings on the rad valves to try and balance things out, but without success so far. Could someone suggest a solution please as I've run out of ideas. Thankyou
Bruce K

Riley · Mar 23, 2019

What sort of radiators are they any pics?? Are both non working rads on the same pipes? Can you close all the other rads and force heat to the offending ones?

BruceK · Mar 23, 2019

Thanks for the quick response Riley. They're standard single panel rads, with standard valves on 15mm pipework. They are on the same branch, yes. The ends that do get hot get very hot and the pipework at both ends is too hot to touch.

Riley · Mar 23, 2019

Ever drained em? They look old. What sort of heating system do you have ? Sealed or tank in loft? I’d be thinking mucky inside. You could try removing the radiator and giving it a blast through with a garden hose and seeing if and sludge is obvious

BruceK · Mar 23, 2019

They are quite old Riley but had new valves recently because the knob on one of the old ones sheared off. This involved draining down the system. Not too much sludge. The system is conventional with a tank in the loft. All the other rads on the system (23 altogether) work okay. I was wondering if the flow might be too fast??

Riley · Mar 23, 2019

Unlikely mate. Try and force the heat there first by turning off the other rads

BruceK · Mar 23, 2019

I'll give that a try tomorrow. Thanks for the suggestion. There is plenty of hot water flowing through the radiators though, it's just not rising to the top at one end.

Riley · Mar 23, 2019

Try forcing the heat through but I reckon blocked rad

townfanjon · Mar 23, 2019

Where did the rad valves come from Bruce ?

BruceK · Mar 23, 2019

They came from Travis Perkins. The valves themselves are letting plenty of hot water through and work ok when turned on and off. Trouble is the hot water's going straight out again at the other without having enough time to fully distribute the heat. It's almost like the rad is only half full, except it's hot at one end (inlet end). If the rads were sludged up wouldn't that be likely to affect the bottom more than the top?

Riley · Mar 23, 2019

I’ve had ones where the blockage was top right quarter as you look at it so anything’s possible. I agree unlikely but it could be

BruceK · Mar 23, 2019

I'll keep you updated.

BruceK · Mar 30, 2019

Well it does seem as if too much flow might have been part of the problem anyway. I turned both valves not quite off and heat distribution is greatly improved. We'll see how it goes.

doitmyself · Mar 31, 2019

BruceK said:
Well it does seem as if too much flow might have been part of the problem anyway. I turned both valves not quite off and heat distribution is greatly improved. We'll see how it goes.

Just for your information: the flow through a 1kW radiator is between 0.7 and 1.4 litres per minute - depending on the temperature drop across the rad.

Millsy 82 · Mar 31, 2019

Start with the basics fully open both valves on either end of rad turn them anticlockwise. Then turn off all other radiators which will force water through these. Leave it like that until the rads get hot all over then turn the others back on.

BruceK · Mar 31, 2019

Thanks for the advice 'doitmyself' and Millsy 82. Once they're hot and the others turned back on would you suggest leaving these two fully open or should the valves be closed any?

doitmyself · Mar 31, 2019

BruceK said:
Thanks for the advice 'doitmyself' and Millsy 82. Once they're hot and the others turned back on would you suggest leaving these two fully open or should the valves be closed any?

It sounds as if your system has never been balanced, which means adjusting the lockshield valve (opposite end to TRV) on each rad to produce the correct flow through the rad.

Radiators hot at one end and cold at the other.

BruceK

Riley

Plumbers Arms member

BruceK

Riley

Plumbers Arms member

BruceK

Riley

Plumbers Arms member

BruceK

Riley

Plumbers Arms member

townfanjon

BruceK

Riley

Plumbers Arms member

BruceK

BruceK

doitmyself

Millsy 82

Plumbers Arms member

BruceK

doitmyself

Similar plumbing topics