Radiator cold at bottom - hot at top

chopps

One of my radiators is not evenly hot (cold at bottom).
I have read that this can be caused by a faulty TRV or sludge at the bottom reducing flow.
Some questions though -

1. Can I 'fix' it by opening the lockshield valve to allow more water to flow through ?
2. What temperature range do TRV's operate at ? meaning if it's on the highest setting (no.5) should it still be 'open' if the room temperature was say around 24 C ?
3. how do you correctly set up all the lock valves to 'balance' the system ?

cynicalgit_2

Have you tried bleeding the rad?

chopps

cynicalgit wrote: »

Have you tried bleeding the rad?

No, because it's hot at top and cold at bottom - not the other way round which is when bleeding is indicated.

keystone

chopps wrote: »

One of my radiators is not evenly hot (cold at bottom).
I have read that this can be caused by a faulty TRV or sludge at the bottom reducing flow.
Some questions though -

1. Can I 'fix' it by opening the lockshield valve to allow more water to flow through ?
2. What temperature range do TRV's operate at ? meaning if it's on the highest setting (no.5) should it still be 'open' if the room temperature was say around 24 C ?
3. how do you correctly set up all the lock valves to 'balance' the system ?

I think you have sludge in it. Particularly if the shape of the cold area is roughly parabolic. Isolate it. Drain it. Take it off. Take it outside. Flush through with a hose. Put back on. Refill.

Opening the lockshield valve will just upset the balance of your system.

Depends on the spec of your TRV. TRV obviously functioning or none of the rad would get hot.

Don't go there unless you want someone here to write you a "how to epistle" or you have time to do it. Googling the process might be easier to get a handle on it.

Cheers

chopps

Thanks for the info.
It probably is sludge as it's one of the two radiators downstairs and does seem to have the curved pattern of heating you described.
The radiator is a standard design double panel measuring approx.
48x24 inches - how much water does it hold ?

redpete

chopps wrote: »

1. Can I 'fix' it by opening the lockshield valve to allow more water to flow through ?

The sludge has to go somewhere and it is a closed system. If you flush it out of this radiator by increasing the flowit will go somewhere else, into another rad or the boiler. Best to disconnect the rad and flush out with a hose. I'd then put some anti-sludge stuff in the system to help control the problem.

You should be able to drain it into a washing-up bowl or similar, emptying the bowl a time or two if necessary.

shut both the valves (having noted the position of the lock valve so you can open it to this position when you replace the rad). Undo one of the valve connections with a bowl underneath it, open the bleed valve and the water should flow.

Put plenty of newspaper or rags under the valve to soak up any spillage, the water and especially the sludge can make a real mess if it gets onto carpet. Also be very careful when carrying the rad through the house, black drip marks through to the back door are not an attractive look.

diywhynot

chopps wrote: »

T
The radiator is a standard design double panel measuring approx.
48x24 inches - how much water does it hold ?

See page 8.

chopps

Thanks, about 6 litres it seems - quite heavy too at 30-35 kg.

chopps

So I took it outside and flushed it out in all directions with a hosepipe. Some black coloured water came out but no sludge.
Put it back and filled it up with about 6litres of water (it's a double panel) with some sentinel 100 added to avoid diluting what was already in the system.
Turned it on (no leaks !) but no improvement - still cold at bottom.
Could it be the TRV not fully opening ?
TRV is at top right and lockshield at bottom left corner.
The lockshield valve setting was fully open on this radiator.
TRV valve is a wax pellet type ? Honeywell and quite a large device mounted horizontally on top (return?) pipe.

Myser

Some of the older wax sensor TRVs aren't as reliable as liquid sensor ones.

Try taking the TRV head off completely and see it it makes a difference.

Also check if the TRV pin is stuck underneath by pushing it down with a flat-bladed screwdriver a few times. It should spring back up each time.

chopps

Tried that and the TRV seems ok as pin moves freely and in and out.
Could it be that system needs rebalancing if the 3 upstairs radiators (which are closest to the boiler) are provding an easier water flow than the 2 downstairs ?