In article , Fred wrote:
Thanks Tony, was this a slow or fast thing, my woosh is
pretty fast, say 1Hz.

At a guess I would say that the pressure needle was oscillating
at something like 3-5 times a second: I don't recall any
particular noise but our two boilers feed through a balance
header rather than through the heating circuits.

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