I have just had the heating back on for about two weeks, all the
radiators have been bled but one remains cold and the pipes to and from
the radiator are also cold, I am a diy novice, and give as much detail
as I can think off in the hope somebody has a simple solution. The
radiator is a standard type with a lockshield on the left handside and
a themostatic valve at the right hand side. I thought that maybe it was
full of sludge so I took it off today and although the sludge didnt
seem that bad I took it outside and flushed it with a power hose until
thoroughly clean.
I then thought I check the that the valves were working so I turned on
the thermostatic valve but no water came out as I was expecting (the
central heating was on) but I wasnt sure if it was meant to so I then
put the radiator back on and opened up the lockshield and thermostatic
valves. Imediately the radiator started heating up, this got me
thinking that maybe the radiator was filled from the lefthandside which
seemed the wrong way round but I wasnt too concerned because the
radiator was getting hot, I bled the radiator as it filled up and 90%
of the radiator got very hot except the top right hand side (above the
thermostatic valve), however i never got to the stage when water came
out of the bleed valve, it just stopped bleeding air.

Then I checked it about half an hour later, and was disappointed to
find it was cold/lukewarm throughhout and the pipes to and from the
radiator were also cold, what has gone wrong ?

thanks Paul

"ijabz" wrote in message
oups.com...
I have just had the heating back on for about two weeks, all the
radiators have been bled but one remains cold and the pipes to and from
the radiator are also cold, I am a diy novice, and give as much detail
as I can think off in the hope somebody has a simple solution. The
radiator is a standard type with a lockshield on the left handside and
a themostatic valve at the right hand side. I thought that maybe it was
full of sludge so I took it off today and although the sludge didnt
seem that bad I took it outside and flushed it with a power hose until
thoroughly clean.
I then thought I check the that the valves were working so I turned on
the thermostatic valve but no water came out as I was expecting (the
central heating was on) but I wasnt sure if it was meant to so I then
put the radiator back on and opened up the lockshield and thermostatic
valves. Imediately the radiator started heating up, this got me
thinking that maybe the radiator was filled from the lefthandside which
seemed the wrong way round but I wasnt too concerned because the
radiator was getting hot, I bled the radiator as it filled up and 90%
of the radiator got very hot except the top right hand side (above the
thermostatic valve), however i never got to the stage when water came
out of the bleed valve, it just stopped bleeding air.

Then I checked it about half an hour later, and was disappointed to
find it was cold/lukewarm throughhout and the pipes to and from the
radiator were also cold, what has gone wrong ?

thanks Paul


What type of system do you have?

Sealed - You will have a pressure gauge near or on the boiler and a filling
loop (Flexible pipe connecting between the mains water and the central
heating pipes (usually near the boiler)
If so, you need to add more water to the system (Removing the radiator, then
refilling it will have depressurised the system)

Or do you have a vented system - this has a small water tank in the loft to
keep it topped up.

If so, try and bleed the radiator again, if no joy, check this tank has
water in it!


As for your not getting hot problem...

Sort the system out so you can bleed the offending radiator first, then try
and remove the head of the thermostatic valve, there is usually a ring at
it's base you unscrew, this will enable the head to come off to reveal a pin
(Water shouldn't leak out when you remove the head!) - does this cause the
radiator to get hot - if so, the head needs replacing, if not I would guess
the valve is knackered.

As a lat resort you can try turning off all the other radiators in the
house, set the system to heating only (If you have a hot water tank) and see
if that sorts it.

Sparks...

What type of system do you have?

Sealed - You will have a pressure gauge near or on the boiler and a
filling loop (Flexible pipe connecting between the mains water and the
central heating pipes (usually near the boiler)
If so, you need to add more water to the system (Removing the radiator,
then refilling it will have depressurised the system)


I forgot to say, if your system is sealed, it should be at around 1 bar when
cold.

Sparks...

On Nov 4, 11:05 pm, "Sparks" wrote:
What type of system do you have?

Thanks for quick reply

It is a Vented System ( probably 20 years, small copper pipe
connectors). i think I see where youre coming from with the bleeding,
there may not be enought water in the system to fill the radiator, even
after removing the air, i think I have had this problem from time to
time with other a few other radiators when I have bled them (although
they stayed hot), I wil check this first thing tommorrow.

Ill then see if I can remove the head of the valve, I assume what is a
happening is the radiator is getting hot but then the valve is
calculating the temperature incorrectly and telling the radiator to
cool down again ?

"ijabz" wrote in message
ups.com...


On Nov 4, 11:05 pm, "Sparks" wrote:
What type of system do you have?

Thanks for quick reply

It is a Vented System ( probably 20 years, small copper pipe
connectors). i think I see where youre coming from with the bleeding,
there may not be enought water in the system to fill the radiator, even
after removing the air, i think I have had this problem from time to
time with other a few other radiators when I have bled them (although
they stayed hot), I wil check this first thing tommorrow.

Ill then see if I can remove the head of the valve, I assume what is a
happening is the radiator is getting hot but then the valve is
calculating the temperature incorrectly and telling the radiator to
cool down again ?

Possibly, but as you said in your original post, "I turned on
the thermostatic valve but no water came out" I expect the head or valve is
broken/full of crud - Did you turn it full on?

I expect the heating while filling was due to the rad filling via the
lockshield, I assume you had the heating on at this point, if so, it would
be filling with hot water ;-) but it would go cold soon if there wasn't any
water circulating in or out via the Thermostatic Radiator Valve (TRV)

If either of the valves are off, then the rad will fill from the other, even
if it is normally the outbound flow valve.

You just said "It is a Vented System ( probably 20 years, small copper pipe
connectors)" How small is small?

If this rad was sludge up, then there could be a plug of crud blocking the
TRV - this may be pushed through if you turn off all the other rads in the
house and leave this one full on (on the TRV and the lockshield)

Do you have any inhibitor in the system - you really ought to!

Sparks...

Thanks very much Sparx, the problem appears to be solved, Ill explain
what exactly I did in case of use to other novices

I tried turning off all the other radiators, I couldn't turn off the
hot water because the central heating only works when the hot water is
on, no change, i then tried bleeding the raidator no air or water came
out at all.

I then went up into the loft and there was plenty of water in the
expansion tank (it was 3/4 full), I also checked the temperature it was
warmer than I expected 25%Celcius, but this matched the temperature of
the loft so i guess that is alright, there was also quite alot of noise
from the pipes going into the expansion tank.

I then look at the thermostic valve, our is mounted horizontallly
rather than vertically. I Unscrewed a screw and was then able to pull
the head off. Underneath was a nut with a pin in it, I wasnt sure what
to do so I unscrewed the nu a bit and then took it completely out, a
little bit of sludgy water came out but nothing else much happened. I
then tried twisting the pin with a pair of pliers, suddenly it popped
out about an extra 5mm and the radiator started getting hot at that end
immediately I bled the radiator and the air came out much more quickly
this time, and I now have radiator that has ben hot for an hour now !,


Do you have any inhibitor in the system - you really ought to!
The pipes are 10mm diameter I guess this makes them more suspectible to
sludge, I did think about using corrosion inhibitor but I was worried
about using it because I had read it can make the early signs of
corrosion worse, also I was not really to sure how to train the system
properly, we dont have any draincocks and I was worried about
introducing airlocks.

Paul