Davey wrote:
On Sun, 29 May 2011 12:00:31 +0100

I easily removed a head, and the pin appears to be free, it is
easily moved up and down, with resultant changes in waterflow. But
looking at the Honeywell website, all integral heads seem to be intended
to be mounted horizontally, whereas mine are all vertical. Could this be
the problem? That they are not seeing room air temperature, but are
affected by the heat in the pipe underneath them? If this is the case,
then a one-time drain-down and overall TRV re-orientation may be in
order before winter.
Comments welcome (useful ones, that is).

If it's just the one valve sticking then why not just replace that? If your
system is sealed it's quick and easy to drain down. If not then you can
bung the vent pipe and cold feed at the header tank to create a vacuum
which will allow you (in most cases) to remove the valve concerned, without
draining the system (very little water loss). Better still- new house! Then
take the opportunity to drain down, flush thru, swap valve and refill
adding inhibitor.
Who knows when the previous owners last had it done!

Deano.
--
What else are opposable thumbs for? Get to me at
masterfix{at}btinternet{dot}com