I've decided that one of these auto bypass valves would be a good thing on
my all-TRV system, up til now I've had the TRV head left off the hall
radiator as an uncontrolled bypass rad. So I ordered the Pegler valve from
Screwfix. Before I fit it, is there any trick to calibrate these things
without the use of a pressure gauge? I was expecting some kind of indicator
on the valve to show when it was fully open (I seem to remember seeing some
other model that had this?) and thought that this would provide a good way
of calibrating the thing, but alas, the Pegler valve just has an adjuster
and a confusing calibration chart in the instructions. Well, confusing to
an amatuer plumber without a pressure gauge that is.

Should I send this one back and try and source one with an "open" indicator?
Should I buy expensive pressure measuing kit? Should I just set the control
half way and hope for the best? Should I give up and fit a room stat? :-)

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