In an earlier contribution to this discussion,
Malcolm H wrote:


It's just been pointed out to me that it will be necessary, of
course, also to install a by-pass for the valve which controls the
central heating water flow, otherwise the water will have nowhere to
go!!


That depends on the system design. If it's an S-plan where all the zone
valves will be closed, then yes you need a by-pass. If it's a Y-plan with a
mid-position valve, there is always a path open somewhere - unless *all* the
radiators have TRVs (at least one of which shouldn't have!) and they are all
closed.
--
Cheers,
Set Square
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