Cold Radiator - possible blocked pipe?????

1 May 2010
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United Kingdom
I have a cold radiator.
My system is run off a Bosch greenstar 35di combi and the radiator in question is piped up with a lsv at either end (no trv).
I have checked over the sytem and ascertianed the following -
1. every other rad heats up fine and the system is not airlocked.
2. The flow into the rad is fine and the lsv is fine
3. The return from the rad is fine and the lsv is fine.
I think that the problem is a blockage in the pipework between the return lsv and the return main pipework.
Question is can I use a restorer/chemical to try to unblock this.
I have a mix of copper and hep20 pipework throughout the system
How much would I need and how long do I leave in .
Thanks in advance
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have u closed down the other rads to see if it will then flow throu this rad?
Are both LSV's open enough, if both valves fully open and rad not working now but did before, it's going to be be air or muck.

If there is no flow through the radiator and it's muck, cleanser wont help.
yes i have tried this and also had the valves off and ran the sytem through and the rad is fine. the block is definately in the pipe. I just dont want to have to rip the floor up to get to it. any ideas??
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Just a thought for you,
I had same problem yesterday after having new heat exchange in boiler, running cleanser for 2 weeks and one new rad fitted on existing pipework previous worked fine but was old school, so I messed about for hours taking valves off, sticking a coil drain unblocker to move sediment or air, nothing?? untill I can across This site WHAT A BONUS............... ::
Followed tips
Isolated radiator by tuning all others off, boiler did not like it as there was a clear obstruction somewhere.
Turned on rad in next room with boiler going and all of a sudden there was a big gurgle and air moving and radiator got hot on top only for a few seconds then no more heat? It had to be blocked but where??
So again this time I took off trv and valve body AGAIN and Im not joking when I tell you what I found, a 6 inch piece of cleaning cloth that had been rolled up like a pipe cleaner stuck under valve body!!!!!!!!!!!!!!!!!
Bingo!! but who left it there that is that question...
Upon forensic inspection it looked a lot like that strong blue paper towel stuff that so called tradesman use to wipe there hands with?
Sabotage or what I dont know but without help here it would have cost me at least another visit from SO CALLED PRO WITH GASSAFE REG>
has it got an trv on one side ? is the pin moving up and down freely when u push it (havin taken the trv head off) ?

if still no joy i would take off the rad , attach a hose downstairs and open drain valve...then attach a hose to each valve (one ata time) and let mains pressure shift what ever u might have blocking it
If I tried to flush it with the mains would this not have the potential to damage my boiler?
You sure it's a combi with a sealed system - they make an open vented version of this boiler..?

Take off the rad

Open valves to see which side is blocked.

Close valves

De pressurise system

Remove the valve on the blocked side.

Connect a 15mm compression fitting to the olive & backnut on the pipe, onto a short length of 15mm copper pipe, jubilee clipped onto hosepipe fed out of nearest window.

Ramp up fill pressure of system as high as it will go. You won't get more than 3 bar into system without firing PRV.

If that doesn't clear it you'll be having to enter that marvellous subterranean void beneath the floorboards....

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