In article ,
writes:
On 10 Jan,
(Andrew Gabriel) wrote:
I use a 3-port valve to switch separate upstairs and downstairs
heating zones. I put downstairs on A and upstairs on B, on the
basis that if it broke I can still heat downstairs, and that
indirectly heats upstairs to some extent. Also, downstairs is
heated more than upstairs, so the valve spends more time powered
off than powered up with the synchronous motor stalled.
I did that for about 5 years (together with a preceding one for HW/CH) until
I got fed up with replacing micro switches.
Funny, I see a few reports on here of unreliability of these
things, but we've never had one fail in mine or any of about
3 other family member's systems yours truely ends up maintaining.
They're all 3-port mid position units. Just checked one of them
which is at least 8 years old and it claims to be a British Gas
one (rebadged I'm sure, but don't know who from). One I fitted
in a new system about 6 years ago was Landys and Steaefa and
going very cheap as old stock. Don't know about the others as
I've never had to pay them any attention.
Since changing to 3 two port valves I haven't had to change anything in the
last 8 years (although I should get round to fixing a slight leak on the
spindle of one of the valves one of these days).
For some reason the micro switches in the 3 port valves seem much less
reliable than in 2 port valves, perhaps the valves hunt slightly with mains
volts when in the mid position. I can't think of any other reason.
In the system I designed, I don't use the microswitch as the
valve is driven by a computer, not one of the conventional
circuit arrangements. (I did use it to confirm the valve was
working initially, but I needed that computer input back for
something more important.) There is a second microswitch which
is used internally to lock in mid position.
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]