In article , OldScrawn
wrote:
the modern ones can be used with ordinary taps with the expansion
being taken up by the feed pipe if long enough, or expansion
vessel if not.

Not sure about that. The one I just fitted has a 3 bar pressure
relief valve which you are supposed to vent somewhere safe

That's there as a safety measure if things go wrong (i.e. the stat
fails or you haven't provided the required length of feed pipe or
expansion vessel) not to handle normal expansion

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
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