Top of radiators hot but lower half cool. Why?

[boilerfrustration]

My tenant has rung me to say that he can't get full heat on the radiators. I went to inspect and found that the heat was concentrated at the top half. The bottom off was warm to cold.

There are no boilers in any of the properties which rely on communal heating fed by a master boiler.

I assumed the radiators needed bleeding but found there was no air. I've tried turning all the rads on and off several time but that doesn't work.

I spoke to a couple of my neighbours who said their rads were very hot. The rads in the common areas are also piping hot.

Can anyone tell me what might be the problem?

 

[ChrisR]

Rads heat from the top down, so it could be lack of flow. Is the flow end pipe really hot? The other end shouldn't be much less hot. If it is, the water's too slow, and cooling down..

The other likely cause is SLUDGE. It collects at the bottom of rads. Easiest way to deal with that in the situation would be to take a rad off and flush it with a hosepipe.

 

[boilerfrustration]

I don't think it's sludge because the rads were newly installed last year.

I'll check the flow end pipe tomorrow to see if it's hotter than the other side. If lack of flow is causing heat deprivation, how do I resolve the problem?

 

[MANDATE]

by opening the lockshield valve a little more. Thats the valve on the opposite side to the on/off valve fitted with plain plastic cap

 

[boilerfrustration]

I've just opened the lock shield valve on all but one radiator. The heat to the top half of the rads has increased but only marginally to the bottom half.

Oddly, one radiator in the flat has always been piping hot from top to bottom but it's the other 3 that are the problem.

I'm totally baffled as to the cause.

 

[boilerfrustration]

I've now opened the lock shields on all the radiators except the first in the chain which is piping hot. The top half of the others is a bit hotter but still the bottom is only warm.

The pipe to the valve is cool but the pipe to the lock shield is hot (although not piping hot).

Any more suggestions?

 

[MANDATE]

OK so you've got lockshield valves on one side.
Are the valves on the opposite side of a similar type or are they thermostatic radiator valves which may not be fully open or even fitted the wrong way round
If the problem is not the radiators or the valves it suggests a partial blockage in the pipe work.
It might be an idea to remove a radiator, then run off some water from each valve. You may notice a difference in flow and it might even flush out some sludge,
You could try closing off three radiators to see the effect on one of the problem radiators.
If one radiator is OK it does not suggest a pump problem

 

[boilerfrustration]

It definitely isn't a pump problem because the radiators in the rest of the building which is 6 stories high are piping hot. My flat is raised ground floor and I do have at least one radiators working perfectly.

I'm going to do as you suggest and turn off all but one rad to see what effect it has on the others.

Thanks.

 

[BingoBongo]

are they top feed radiators by any chance i.e trv at the top?

 

[boilerfrustration]

They are fed from the bottom and the pipes feeding the radiators are only warm.

 

[boilerfrustration]

Other than the rad which is working properly, I switched off all the other rads bar one which heated up more at the top but is still struggling to heat up from half way down onwards.

 

[boilerfrustration]

Is is possible that the thermostatic valves are damaged and preventing hot water from entering the radiators?

 

[MANDATE]

I would say yes!
But also some have plastic pins that can be lifted in order to limit the amount of opening and closing.
It may be you can't open them fully until the pins are lowered.

 

[plstering]

why not flush the lot m8
drain it take the rad off then flush the lot using a out doors mains tap se fenox fill it let it run as there mite be **** in it from the refit as you said its not that old when it was fitted was it drained and flushed and checked