Central Heating Flush

[slid_away]

Hi All
I added a sludge remover to my central heating system 2 weeks ago.
Today I have drained the system and flushed it through and added the inhibitor.
The system is back up and running and all the radiators are extremely hot except the one which I used to flush through. I flushed until the water ran clear.
I have bled every radiator until only water comes through and turned off every radiator except the one which is cold, but still it remains stone cold. Even the down pipes into the radiator are stone cold. I have also taken off the thermostat to check that the pin is not stuck, which it is not.
For info, the cold radiator is down stairs nearest the boiler.
Any help would be greatly appreciated
Many Thanks

[AlBags]

And you are certain the lockshield is clear and open?
No circulation through that rad only, means air lock in hot or return on that rad leg .. Not microbore is it?
Try turning off all rads except that one and running pump full speed.

[slid_away]

I've had all the rad's off apart from the cold one and it is very slowly warming up now. Not sure what mircobore is I'm afraid!! lol
I'm going to keep running it for the next few days, bleeding to make sure and see how I go

[weas]

is the return value fully open , turn the pump up full and leave over night.

[heathfield]

FYI, Microbore is the 10mm and 8 mm sizes of pipe.

[tezestwing]

I think it has clogged up with sludge, I would be inclined to remove the troubled rad very carefully though,place loads of old towels etc down then measure length and remove the tails and manually flush it out with mains hose in the garden tap the sides of the rad with wood as you do it to remove all deposits,(PTFE) tape the tails 10 turns,reinsert into previous measurement, clean cones and unions, then refit ,then refill and vent from flow side only until full of water then open lock shield to balance out,re-pressure combi systems HTH Tez