Bottom radiator stopped working

[Stringman_uk]

Hi all
4 story house 8 rads.
I drained down our radiator system yesterday to clean the heat exchanger. I drained the system using the drain valve on one of the bottom radiators.
I topped the system up, bled all the radiators from top floor down.
All the radiators work fine with the exception of the bottom radiator ( the one I used to drain the system) it is stone cold as are both the pipes.
It doesnt have TRV and both valves are fully open.
I tried bleeding the rad again and there was no air. When I loosened off the drain valve water started to come out.

I am most confused as nothing has changed to the rads.

I dont think it could be a balancing problem as I I only opened up the very top radiator valve ( the room rarely gets used so it has been switched off)
Any advice as to what it could be? and how to fix it?
I was looking at doing the bucket test but thought I would ask first.
Many Thanks

 

[terryplumb]

Close all other radiators by their TRV ( or wheel head if no TRV ,don't touch their lockshields )Run heating and see if cold rad now heats up.

 

[Stringman_uk]

terry
thanks for the prompt reply.
Can I just confirm that the wheel head is the "incoming valve" the the lockshield is on the return pipe?

Thanks

 

[terryplumb]

terry
thanks for the prompt reply.
Can I just confirm that the wheel head is the "incoming valve" the the lockshield is on the return pipe?

Thanks

Not necessarily, the lockshield usually has a plastic cap ,to prevent tampering, and the valve for what you use to control the radiator has a handle for ease of turning). Although the lockshield is typically fitted on the return ,it doesn't make any difference on a basic panel radiator, if it's fitted on the flow

 

[Stringman_uk]

terry again thanks
looking at the cold rad the valves look the same, as in they both have plastic covers but one is larger than the other!

 

[terryplumb]

Show us pics of both valves.
Which one do you normally use to turn rad on or off ?
Or have you never needed to ?

 

[Stringman_uk]

sorry for the complete lack of response
work has been mad and I am a way for a couple of weeks.
I will follow up when I am back.
Thanks

 

[Stringman_uk]

Work has finally calmed down a bit but now manflu!!
I had put in some cleaner when I first topped up the system, which now needs to be drained.
Should I try the above tests before draining and refilling or hope that the refilling cures it?

Another question. I have to had inhibitor. but didnt buy the pressurised applicator.
The radiator on the 3rd floor has a speed fit connector. So could I disconnect the pipe and pour the inhibitor in the pipe before re pressurising the system?

Thanks

 

[terryplumb]

If you are going to drain the system and flush out the cleanser,there is no point trying to get one radiator working that currently doesn't ,other than the fact that lack of circulation through that rad would have resulted in the cleanser doing nothing in that rad or the pipe branches to it.
What prompted you to add cleanser in the first place ?

 

[oldbuffer]

Try bleeding again, lowest to highest, with the heating off.

 

[Stringman_uk]

If you are going to drain the system and flush out the cleanser,there is no point trying to get one radiator working that currently doesn't ,other than the fact that lack of circulation through that rad would have resulted in the cleanser doing nothing in that rad or the pipe branches to it.
What prompted you to add cleanser in the first place ?

the whole system was full of gunk and i thought it wouldnt do any harm it was sentinel x400
I am hoping that as I drain ( the drain is on the non working rad) and flush it will cure the problem

 

[Stringman_uk]

Further update,
I drained out the system. mentioned it to my wife and she said "oh the radiator was working fine yesterday"!!!
After draining and refilling ( to flush out) lo and behold the radiator was the only one cold. I bled it- no air.
Thought I would loosen the drain plug. A big gurgle and then the water flowed.
Radiator immediately got hot!
thanks all