In an earlier contribution to this discussion,
Mike wrote:


Not quite! You need a water path at all times when the *pump* is
running - including any over-run period *after* the boiler stops
firing - by which time all zone valves may be closed!

Or an electronic sensing pump such as the Grundfos Alpha

I don't see how that helps! It's the *boiler* which needs the flow to keep
going after it stops firing in order to carry the residual heat away and
prevent the over-heat cutout from tripping. No amount of electronic sensing
can maintain the flow if there ain't anywhere for it to go!
--
Cheers,
Set Square
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