Hmmmmm.... this is getting strange, but your theory below might shed some
light on my latest findings :-

I've just been meddling about with the valve in the garage with a
multimeter.

1. The valve does have free movement albeit limited to about 30° max. Does
that seem right or should it be more like 80-90° ?

2. With the control switch set on 'water plus heat' the motor starts
turning, pressumably to open the valve. Looking at the motor direction of
rotation, this should make the quadrant gear move CCW downwards. At this
point I levered the quadrant down manually to trigger the microswitch, but
nothing happened and the motor kept on turning.

3. Thinking that the microswitch was faulty, I turned my attention to that.
It has three terminals but only 2 wires connected. A black wire underneath
and a white wire in the middle and nothing connected to the top terminal. I
removed the microswitch and tried continuity testing it. Between the two
connected terminals it was a broken open circuit until the switch was
depressed, then continuity was made. When I tested across the two end
terminals I just got a widely fluctuating resistance of 10-70 ohms.

4. ...this is where I loose the plot ! Okay here goes..., with the black &
white wires hanging loose but in a safe position, I switched on the system
and the synchron motor starts turning. I'm not sure why, but I decided to
switch off the system again and connect the black & white terminals together
expecting the motor to stop. But when I switched on the system, the motor
started turning again !!!

My house is a late 60's semi which has a Vulcan boiler , tower 672B zone
valve & 102E randall controller. Some of it was fitted in the 70s and maybe
mods were done in the 80s

Can anyone enlighten me on this as I'm lost

cheers
IJ











"Andy Hall" wrote in message
...
On Fri, 19 Sep 2003 20:15:54 +0100, Ed Sirett
wrote:

BigWallop wrote:


Q11. I've just bought replacement sychron motor, but I can tell
which
position the gear quandrant should be in when I mount the motor in
position.
All I can tell is when the motor is hanging loose and I switch W+H,
then
motor activates without stopping.


A synchron motor, as with any standard motor, will continue to turn
when
energised until told to stop by some kind of switching system. The
small
micro-switch in the motorised valve is such a system.

With the plain 2 port valve the motor simply winds the valve open and
the valve is not able to turn any further so the motor stops - crude but
generally very reliable.



On the subject of these zone or diverter valves with spring returns,
I am sure I can remember that when I installed my first system (late
seventies), the 2 port valves that I used were motorised in both
directions - i.e. no spring return.

IIRC, the motor had two windings or some means of effecting reverse
and there was a live to drive it to open and another to drive it to
close. Then the room and cylinder thermostats were change-over
switches to do this. There was an auxilliary switch as now to
provide the demand live to the boiler.

Do you remember those and when and why they changed? This seems like
a better way to do the job than a motor powered against a spring.


.andy

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