On 02/11/2016 21:12, Harry Bloomfield wrote:
brought next idea :
Seems like a chunk of work for something that you might (or might not)
need once every 10-20 years - why not just feel the pipes and measure
the voltage in the relevant locations? That's worked for me on the
rare occasions things have failed.
If you're short of something to do I can find you a few (dozen) jobs ;-)

Well, much more frequently than that, every few years in fact. I derive
great enjoyment from finding ways to make my life easier, such would
make my life easier - call it a hobby or even DIY.

My heating failed yesterday. It took me a while to work out that the
room stat wasn't calling for heat due to its batteries having failed.
This would make it quickly obvious why the heating wasn't working - no
call for heat.

When I did some extension work about 10 years ago I fitted a new boiler
and pressurised DHW cylinder and split my system into 2 heating zones
(with individual timer/stats), 1 towel rad zone (with timer), 1 DHW
"zone" (with timer) and added a DHW recirculation loop (timer integrated
with pump) - all with 2-port valves. Since then the boiler and the
expansion vessel have each failed once and I've changed the stat
batteries once (the LCD display being blank was the hint I needed) but
everything else has been fine.
Apart from this, and in other houses, over forty years I think I've had
to replace two dead pumps, three 3-port valve heads (two of them had
broken microswitches), one room stat, one immersion heater and one ABV.
All were easy to identify and fix.
Based on my experiences, if you've got a 3-port valve and want to
improve reliability you might get more bang for your time by replacing
it with two 2-port valves rather than devising a monitoring system.