rad hot at top, cool at bottom

[TonyDav]

The radiator in my lounge, which I think is the last one in the system, is hot at the top and cooler at the bottom. Thinking this could be a build-up of sludge, and as the rad was 24 years old, I replaced it with a convector rad. The problem is till there! Does anyone have experience of the same sort of problem?

Thanks in advance!

Tony

 

[ianniann]

Hot at the top and cold at the bottom indicates a very restricted water flow. What little hot water makes it into the radiator sits at the top. It may not be anything to do with the radiator itself, but could be the pipework that is gunged up.

 

[TonyDav]

Hot at the top and cold at the bottom indicates a very restricted water flow. What little hot water makes it into the radiator sits at the top. It may not be anything to do with the radiator itself, but could be the pipework that is gunged up.

The odd thing is ianniann that all the other rads are working perfectly. I was wondering if perhaps the pump may be failing and just not pushing that last little bit to get the water all round the system?

 

[MANDATE]

I have similar situation, but only when room temperature has been reached and is in a 'longish' cooling down period. With pump not running and no flow its to be expected as hot water rises. With pump running its hot all over.
I don't see it as a problem.

 

[jackthom]

The odd thing is ianniann that all the other rads are working perfectly. I was wondering if perhaps the pump may be failing and just not pushing that last little bit to get the water all round the system?

Is the pump set to maximum speed and has the system been balanced?

If the pump is already running flat out you may need to restrict the flow through some of the other radiators to encourage more hot water to take the longer path via the lounge radiator.

 

[TonyDav]

The odd thing is ianniann that all the other rads are working perfectly. I was wondering if perhaps the pump may be failing and just not pushing that last little bit to get the water all round the system?

Is the pump set to maximum speed and has the system been balanced?

If the pump is already running flat out you may need to restrict the flow through some of the other radiators to encourage more hot water to take the longer path via the lounge radiator.

Have tried running on max speed and also turning it down to 2 but no difference. The rad takes a long time to get heat through from cold. I'll try balancing the system and see what transpires.

Thanks to everyone for their help! Obviously, if anyone else has any ideas, I'd be happy to hear them.

Tony

 

[Biguns]

Have you tried opening the lock shield valve a bit further

 

[TonyDav]

Have you tried opening the lock shield valve a bit further

Sorry to appear ignorant but what is the lock shield valve?

 

[Biguns]

The radiator hopefully has 2 valves. On one side is the valve possibly TRV that you use to control temperature and on and off. The other side is the lockshield, used to increase or decrease flow through the radiator.

 

[jackthom]

Deleted: Beat me to it.

 

[TonyDav]

The radiator hopefully has 2 valves. On one side is the valve possibly TRV that you use to control temperature and on and off. The other side is the lockshield, used to increase or decrease flow through the radiator.

I've tried increasing and decreasing the flow through the rad. It doesn't seem to make much difference. I did realise early on that I'd put the bleed valve on the wrong end of the rad and had to change it round. To do this I had to drain off some water, which I did through the bleed valve, figuring that once the water stopped, the level would be OK to remove the valve. What I did notice, even though both valves were shut off, was that the pipe on the return side of the rad was getting warm, even though it was cold when I started the process.

 

[Biguns]

Turn all other rads off, leave this one on. What happens then?

 

[TonyDav]

Turn all other rads off, leave this one on. What happens then?

OK will try that!

 

[TonyDav]

Well, finally I have a radiator that is hot from top to bottom!

My thanks to all who gave help and advice on this problem.

Tony

 

[Biguns]

I think this needs to be applied

http://www.diydata.com/projects/centralheating/balancing/radiator_balancing.php

Regards Bill