Lukewarm radiator

[Parcival]

I have posted on here before about this but now have a further question I would like advice on please......

In summary......
We have a modern 4 storey house with gas central heating provided by a Vaillant system boiler.
On the ground floor we have a radiator in the hall that gets very hot and another in the kitchen that barely gets lukewarm (it has always been like this). All the rads on the other floors get properly hot. All the rads have Drayton TRV's except the one in the hall.

The system has been checked and balanced by various plumbers over the years without ever being able to get heat into the kitchen radiator. The TRV on the kitchen rad has been checked and the pin moves up and down freely.

The TRV on this kitchen rad seems to be on the wrong side but I am assured this makes no difference. Where the hot water comes into the kitchen rad (opposite end to the TRV) the pipe is very hot so hot water appears to be there but very little gets into the rad. The rad itself is a double and the rear panel gets warmer than the front panel.

Question is - could the TRV have some internal workings that prevent the hot water getting in to the rad even though the pin moves up and down.....

 

[Dean744PiN5]

what model vaillant?

 

[gasmanstu72]

best thing to do would be to change the TRV. it could be stuck even though the pin is moving.
shut down the rad valves and take the rad off, have a bucket handy and then open the valves to see if water comes out at a decent rate, if it just trickles out this would suggest you have a blockage.

 

[it's not that hard]

I am sure that a plumber will have tried this but just incase, the first thing to try with any radiator not getting hot is to shut off all the other rads,letting the water circulate around this one,it could push any air out,
but it's strange that one side is getting warm and not the other side,I'm starting to think there could be a blockage maybe some paste just inside where the valve is stopping the front from circulating.

 

[Parcival]

Thanks for your replies.
I am not sure what exact model the boiler is apart from the fact it is an EcoTec.
Think it's best to get the rad off to have a look and get rid of the TRV as it's not really required anyway.

 

[Dean744PiN5]

Thanks for your replies.
I am not sure what exact model the boiler is apart from the fact it is an EcoTec.
Think it's best to get the rad off to have a look and get rid of the TRV as it's not really required anyway.

The exact model could be a very important part in finding out the problem.

 

[WabbitPoo]

Take off the rad and flush it with a hose.....10 minute job which might yield a simple solution

 

[Parcival]

The boiler is a Vaillant EcoTec Plus 630. It is in the garage which is on the same level as the lukewarm rad in the kitchen. It also has a Magna Clean by the side of it.....

 

[Dean744PiN5]

the 30kw vaillant system boiler takes up the majority of the available pump head , leaving very little capacity for the radiators, most likely the kitchen rad is your index rad and there is not enough capacity in the boilers pump to get full flow through the radiator.

 

[Parcival]

Thanks - not sure I understand what this means. I would only add that we live in one of 6 identical town houses all with the same radiator configuration and boiler. None of the others have the same issue.
To a laymen it seems odd that fully heated water gets to the entrance of the rad but very little gets into the rad itself...

 

[hazetimesfive]

there is a blockage, kind of obvious.

 

[Agile]

Water is flowing through your rad.

Its not a matter of the hot water getting there and going no further.

It is going further but so slowly that it loses its heat so the return and the rad is cooler.

As suggested do the bucket test.

Tony