How do I identify "old" lockshields?


11 Mar 2006
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United Kingdom
I wish to install TRVs on my radiators (except the 2 nearest to the room thermostats). The system dates from ca 1970.
The caps on all the rads are identical at both ends and (square nut approx 7mm) but flimsy and broken and so I cannot turn rads on and off. More importantly, visually there is no difference between the valve and the lockshield. As the system is well balanced at present (all rads heat up well) I would prefer not to change the settings of the lockshields and just touch the valves. How do I easily identify which end is the lockshield and which is the valve?
Any help would be appreciated.
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At that age, given the cost of the valves, you may as well change all the valves. It isn't that hard to balance the valves, and the TRVs will correct any small inaccuracies.
you can easily identify which end is the "flow" where the "wheel head" is fitted, this is also the end where the trv is supposed to be fitted, but it is not now so important with the introduction of reversible flow TRV's, but due to other problems it is best to get them the right way round as it can cause problems which will have been covered on here many times. It is the pipe which enters the radiator which gets hottest first presuming you are on a twin pipe system. Wrap a small bit of tape round this pipe to remind yourself and check it a few times it should always feel hotter than the other side the "return" or "lock shield" end.

Hope that helps

Regards Clive
It is better to put the TRVs on the return end of the rad, they are then less affected by the incoming water temperature. Though that's the theory, it's only domestic heating after all, which as a controlled process is a joke.
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Thank you for the advice on identifying the flow and return ends. On the basis of 2 opinions there seems to be a 50/50 split as to which end the valve should go on and I've noticed from other posts that there seems to be an ongoing debate about this.
So just put them on the end which seems the most sensible in that particular room and don't give it a second thought.

TRV';s are totally inadequate to control the heat in a room anyway, if I had my way all systems would have to be corrctly rad sized and balanced and stop at that. But the powers that bee make me fit trv's.

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