Cold Radiator

[markbutcher355]

I have a dead radiator. Its the one at the end of the run and the system is plumbed with 15mm pipe. The system pump was replaced two years ago. All the other radiators are fine. The feed pipe is hot to touch but the exit pipe is cold back to the preceding radiator.

The first thing I did was replace the thermo valve. The old one was fine. I opened the valve while I changed it - good flow. Then I took the radiator off and flushed it. Plenty of crud but good flow afterwards. I attached a hose to the exit side pipework and when I opened the valve some crud but again, good flow. I put it all back together bled the rad and expected heat. None. Just the same inlet pipe hot, exit pipe cold, radiator cold.

I removed the bleed and a good strong flow of water filled my bucket. The water got warm after a pint or four. Still no heat. No air lock, no blockage, valves OK. Rest of the system fine. I tried closing all the other rads and turning the pump to full speed, no change.

Anybody any ideas?

 

[sonray ltd]

if you you have flow from the flow/return pipework when rad removed
can't see why your not getting any flow when rad replaced
as you say you have a clean rad, both valves working.

take the trv top of for now and run the system with it off.

you say you have shut all the other rads and left that one open.
so the circulation must be going somewhere.

if you say the rad before it is ok then you shoul be able to shut that one and the heat will go to the cold one.

 

[markbutcher355]

Thanks Sonray.

I am completely stumped. I have flow in the lnlet and outflow pipes with the radiator off. I flushed it and there is flow through the radiator. The valves are fine and manually set open and with the radiator installed and the bleed nipple removed the very healthy flow eventually gets warm.

Just no flow through the radiator even with the others turned off!

 

[buffy27]

whats the craic
when u say 15mm pipe runs do u mean they are individual runs to a manifold.if not the problem may b somewhere else along the system , likely reurn from this rad.. what u are saying is not making logical sence to me.because every thing is working perfectly and still no heat. i think u have over looked some thing small maybe.swap the rad valves.flush whole system and re balance.has this rad ever worked.
where exactly is the circulating pump in relation to this rad.

 

[traineedrip]

drastic but can you not swop the dodgy rad with a known working one? see if the fault follows that rad?

 

[kes36]

buffy is right, has this rad ever worked. balancing the rads should work arter checking there is no blockages in the rad or pipework. is the pump circulating? if so, is it pumping to full capacity. has the rad ever worked? could it be piped up with 2 flows or 2 returns?