Rad not heating

Luckysasha

The rad in one of our rooms is not heating up much while the rest of the house is roasting. Rad is in daughters room and has TRV fitted. The pipes going to the TRV side are lukewarm at best while the pipe at the non TRV side is hot to the touch. The rad itself only heats about the top 1/3 of the rad so that rules out an airlock. The bottom 2/3 stay cool no matter how long the rad is on. I swapped the TRV with another one in the house and checked the plunger was moving freely so that's all fine. I opened the vent on the top of the rad and ran the water for a minute or two. The water ran clear so I'm guessing it's not a sludge build up. The system is approx 5 years old

K.Flyer

Turn off all the other rads and allow it to run for a while (20 - 30 mins) and see if that helps.
After turning all of the other rads back on again, see if it stays hot or cools back down.
If it cools down, remove the cap on the valve at the other end of the radiator and turn it a half turn anti-clockwise and see if that improves things.

Luckysasha

Thanks I will try that

Luckysasha

Ok done as suggested. The offending rad only heated up the same amount with all the others off. When I turned all the other rads back on the offending rad stayed the same temp. No change. The non TRV valve is fully open and the pipework going to it got very hot while the TRV pipework stays cool in both situations.

K.Flyer

It does sound like you have a blockage somewhere, even possible that the radiator is half full of sludge.
When you had the trv off, did the pin in the middle of the valve move up and down freely. Did you try it with the trv removed?

Luckysasha

Yep the plunger on the TRV side is free. The non TRV side pipe gets extremely hot but no matter how I adjust the valve on that side the heat won't go through the valve in to the rad. The pipe on the TRV side doesn't get above warm. Would the valve on the non TRV side be faulty ?

Dtp1979

Luckysasha wrote: »

Yep the plunger on the TRV side is free. The non TRV side pipe gets extremely hot but no matter how I adjust the valve on that side the heat won't go through the valve in to the rad. The pipe on the TRV side doesn't get above warm. Would the valve on the non TRV side be faulty ?

Hit the valve a few gently taps.
Did you turn off the balance valve on the cylinder when you had the rads turned off?

Luckysasha

Didn't touch the balancing valve on the cylinder. I presume you mean the red handwheel valve on the pipe going to the bottom of the coil. Its fully open at the moment.

Dtp1979

Luckysasha wrote: »

Didn't touch the balancing valve on the cylinder. I presume you mean the red handwheel valve on the pipe going to the bottom of the coil. Its fully open at the moment.

It shouldn't be fully open at any time. Close it fully and turn off all rads that are heating. Turn on boiler for half an hour. Keep us updated

Luckysasha

Ok I will try that in the morning thanks. Roughly what position should the cylinder valve be at ? If I leave it fully closed Am I right in thinking there will be no hot water in the taps.

Dtp1979

Luckysasha wrote: »

Ok I will try that in the morning thanks. Roughly what position should the cylinder valve be at ? If I leave it fully closed Am I right in thinking there will be no hot water in the taps.

Yes. But only close it for the purpose of getting the rad working. In normal operation, fully close it, and open one full turn

Luckysasha

Great thanks again. I will keep you posted.

Luckysasha

Ok tried as you suggested. The offending rad heated up slightly more than usual but not a whole lot over a 30 min period with the cylinder valve fully closed. However the rad in another room nearest the cylinder wouldn't turn off so this may have affected the results. The rad like all others has a TRV and I set it at zero but the water was being forced in to the rad somehow. I swapped out the TRV but it was still the same. So I set the cylinder valve as you suggested a full turn open and left it at that

Dtp1979

Luckysasha wrote: »

Ok tried as you suggested. The offending rad heated up slightly more than usual but not a whole lot over a 30 min period with the cylinder valve fully closed. However the rad in another room nearest the cylinder wouldn't turn off so this may have affected the results. The rad like all others has a TRV and I set it at zero but the water was being forced in to the rad somehow. I swapped out the TRV but it was still the same. So I set the cylinder valve as you suggested a full turn open and left it at that

If the trv won't close, just close the valve on other side of the rad. You'll probably need a spanner or pliers to do it

Luckysasha

Thanks off I go again !!! I noticed out at the boiler I have an expansion vessel but I can't see a pressure gauge si I presume the system is self regulating

Luckysasha

Ok some progress. With all the other rads off and the cylinder balancing valve closed the offending rad heated up to about 80% after 25 mins. So I turned all the other rads back on and opened the cylinder valve 1 full turn and ran the system for 30 mins. I seem to be back to square one I'm afraid. All other rads warm and the offending rad only about the top 30% lukewarm