Three cold radiators...

[WesleyP]

Hello, it's that time of year again, although I did notice this problem last time we had the heating on before summer. The three radiators in the living room, at the furthest end of the house from the Baxi Combi boiler, don't get warm. The one I can easily get to at the moment..the pipe to the raditaor is hot, but the rad is stone cold. It is switched on! After the heating has been on a while, I also get some knocking sound, like water hammer, which goes with fiddling about with various radiators. I did try bleeding one of the living room rads, didn't make a difference. The system was powerflushed a couple of years ago. Can anybody advise please? Thanks.

 

[PrenticeBoyofDerry]

If the rads have TRV, it could be that they have seized.
This is the easiest job, remove the the of the control knob, this will reveal the head of the TRV. This will need to be pushed up/down to free it.

 

[WesleyP]

They are just ordinary valves

 

[PrenticeBoyofDerry]

They are just ordinary valves

So not thermally controlled then? Still check they are open and not seized closed.
Have you bled them all?

The other not wet thing to do is check the system is balanced. If you close the other radiators off do the cold rads get warm?

 

[WesleyP]

Next job on the list to close all the others and see what happens

 

[WesleyP]

All rads seem to be full of water. All rads closed except the three cold ones in the living room, One of the mas come on good and hot. The other has a warm feed pipe to the isolating valve, the third is still stone cold.

 

[PrenticeBoyofDerry]

Check again for air trapped by bleeding, if still not warming. Then you are going to need to crack some nuts open to check that water is actually getting through and no blockages or sludge. If that is okay then could be faulty valves.