Should I try to adjust the lockshield valve of a radiator with a TRV?

@TonyC · Oct 20, 2017

When British Gas installed my new boiler, they also put TRVs and new lockshield valves on the radiators in the bedrooms of my house.

I’ve not been very happy with the performance of one of the radiators since then. Even when the TRV is on its highest setting, the radiator does not get very warm. The pipe entering the TRV becomes very hot, as does the small section of the valve leading into the body of radiator, but the radiator itself barely feels warm.

I don’t think the radiator is full of sludge. There has been Fernox MB1 and F1 in the system for as long as I can remember. And, at the annual boiler service, the MagnaClean is inspected and is always practically clean.

I am just wondering whether this radiator is perhaps one of the farthest away from the pump and that opening the lockshield valve a little (half a turn or so) might alleviate the problem. However, I still recall the British Gas installer telling me that the lockshield valves are factory set and should not be adjusted. Logically, that doesn’t seem right to me. It would basically be saying that the radiators with the TRVs do not need to participate in system balancing.

Any thoughts please? Would it be OK to try opening the lockshield valve a little?

steadyon · Oct 20, 2017

1. They are not factory set, although, depending on make, they are often supplied closed.
2. The system should be balanced. Essentially this means that all radiators should get equally hot pretty much in the same time. (There will always be some lag to the ones furthest from the heat source).
3. You could try opening up the lock shield. Remove cap, close it fully, counting the number of 1/8 turns necessary to close, then open back to the original position and open half a turn more. If that doesn't work, try an extra 1/2 turn open, but if that doesn't work return to original setting. You might then need a heating engineer to investigate further and perhaps balance the whole system.
4. If you are a more adventurous / experienced DIYer, look up the sticky thread on balancing.

@TonyC · Oct 20, 2017

steadyon said:
You could try opening up the lock shield. Remove cap, close it fully, counting the number of 1/8 turns necessary to close, then open back to the original position and open half a turn more. If that doesn't work, try an extra 1/2 turn open, but if that doesn't work return to original setting. You might then need a heating engineer to investigate further and perhaps balance the whole system.

Thanks for that. However, why should I first close the valve counting the number of 1/8 turns? Why not simply try opening the valve 1/2 turn? If I know by how much I have opened the valve, I can always return the valve to its original setting.
I have a HomeCare agreement with British Gas, so I can always call them out if necessary.