Radiator cold at the bottom

DrPhilG

I've got oil fired central heating, and for the last week or so I've had 1 room with the radiator acting up. It gets just about luke warm at the top third, but the bottom is stone cold.

I assumed that it was blocked up with sludge, so I took it off and flushed it outside with a hose, but it made no difference. Also whilst it did empty out with black water, it wasn't really thick or sludgy like I expected.

So is there any other possible issue? Or was the blockage just too thick to clear out? I've never flushed a rad before so I wasn't sure what to expect. I've been considering replacing the rad in that room anyway with something fancy as we redecorated recently, but no point doing that until I know that there's isn't something else wrong.

Sleeper12

Sludge can be a misleading name. It can be almost solid. A garden hose isn't really a suitable replacement for a power flush. Power flush uses chemicals to soften and break up the sludge.

If trying the hose again it wouldn't hurt to give it a few taps with a rubber hammer. This might help loosen the sludge

DrPhilG

Cheers, figured that might be the case.

If it's not likely to be anything else I might just bite the bullet and get a new one as its on the agenda anyway.

Lenar3556

It may be a circulation / balancing problem.

Try turning off other radiators and see does this one heat up better

DrPhilG

https://www.boards.ie/discussion/comment/121275835#Comment_121275835

I have a Wiser system in place so each rad has its own control valve. I've tried with every other rad in the house off and just this one up full blast and get the same issue.

Lenar3556

https://www.boards.ie/discussion/comment/121276459#Comment_121276459

Have you tried removing the Drayton TRV head with other radiators off? When you have it removed you could try prodding the centre pin on the valve a number of times to make sure it is opening freely.

DrPhilG

https://www.boards.ie/discussion/comment/121276642#Comment_121276642

Yeah have done both. I switched to a regular valve when doing the flush, easier to control the open and close. Then when I turned the heat on afterwards I tried with the non-smart valve on and fully open, the Wiser valve on and open, and with no valve at all.

The pin seems to be working fine if I push it down with something.

Lenar3556

Sounds pretty comprehensive!

Must be a clogged radiator. Would be well worth adding a couple of bottles of inhibitor to the system when you are replacing it.

DrPhilG

The plot thickens...

I noticed today that 2 of the 3 rads in the hallway were doing the same thing. Bit warm at the top but cold at the bottom.

Our of curiosity I blasted up the heat full bore on all 3 hall rads and on in the cinema (the one with the initial issue) and after half an hour they were all nice and hot.

I then knocked the hall rads off again and the cinema went back to the same issue, warm top and cold bottom.

So now I'm more confused. It's not sludge or it wouldn't have behaved at all. Something else is up.

10-10-20

Sounds like a balance issue. Another rad might be opening nearer to the boiler lessening the pressure at these. Try the same again with all other rads closed at the TRV?

DrPhilG

https://www.boards.ie/discussion/comment/121423201#Comment_121423201

So the cinema one on full and all others off?

10-10-20

https://www.boards.ie/discussion/comment/121423328#Comment_121423328

Well, cinema and hallway on and the rest off. Are both of these likely to be the furthers rads from the boiler on this zone? If so you could try balance back off these if they heat up ok.

DrPhilG

https://www.boards.ie/discussion/comment/121423407#Comment_121423407

Boiler is in the garage away on the other side of the yard.

I had knocked on the cinema rad earlier, getting the same issue.

Just knocked on the 3 hall rads now.

DrPhilG

Update

* turn on the cinema rad only, warm top and cold bottom

* cinema rad on, hallway rads on, cinema rad heats fully

* turn on cinema & hallway, cinema heats. Turn off hallway again, cinema cools a bit at the bottom but not as bad as if the hall was not on for a while.

tikka16751

How many rads are in the cinema?

listermint

Have you balanced the entire system ? Start from square 1 tomorrow spend a while and just balance end to end.

DrPhilG

https://www.boards.ie/discussion/comment/121524690#Comment_121524690

Just 1

DrPhilG

https://www.boards.ie/discussion/comment/121524692#Comment_121524692

I haven't, I'll have to take some time over Christmas and figure that out (I've never done it).

When I say I've never done it, it has been done just not by me. Pretty sure a plumber who was doing some work a few years back balanced the whole place.