Lockshield Valve MUST be on Radiator Output?

10 Jan 2016
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United Kingdom

I'd class my DIY skills and knowledge and reasonably advanced but need some advice about a bog-standard Thermostatic Radiator Valve and Lockshield Valve set that I've just bought from Wickes, their item 11400.

The instructions for these valve state that the Lockshield MUST be fitted on the output/return side of the radiator. My question is why? This would seem to infer that these valves require the flow in one specific direction only, is that right?

The positioning of the pipes, radiator and best position for the TRV might make it more desirable (to avoid crossing-over pipes) to have the Lockshield on the input/flow side of the radiator. What would be the consequences of doing this?

Thanks in advance for any help.
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Valve shutting off properly and flow through valve causing less restriction on how it's made.
Also if some cheaper TRVs are fitted in wrong direction of flow they will "chatter/vibrate" when closing off as pump pushes against spring in valve.
.Thermostatic Radiator Valve and Lockshield Valve set that I've just bought from Wickes, their item 11400.
That item number is not correct. Do you mean 114000?

If so they seem to be contradicting themselves as they say:

This thermostatic radiator valve is designed to be fitted in any orientation and with water flowing in either direction, the valve must not be directly exposed to sunlight and curtains or decorative elements must not stop the air from circulating freely. The loose Tap head or return valve (lockshield) must be fitted on the output side of the radiator.

If the TRV can have water flowing in either direction, that means it is bidirectional and can be fitted on the return. Lockshield valves are nothing special, so I don't see any reason to restrict them to the return. I suspect that, whoever wrote the document was under the impression that the LS valve had to be on the return to work properly; this is not true. The job of an LS valve is to set the maximum flow through the radiator, which it will do whichever end it is on.

Put the valves on how you want.

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