Roger Mills wrote:


It depends on exactly what's happened. If the 'wet' part of the valve has
seized, nothing you do to the actuator (the electrical part) will make any
difference. If the actuator has simply got confused (and it *can* happen!),
powering it down completely - at the FCU which feeds the whole system, not
just at the programmer - may 're-boot' it and make it work properly again.
[If you need some help to determine which it is, come back.]


Also, I can't find out what the manual override lever on the valve is
for!!! Is it supposed to set it to "heating only", "hot water only",
or "both on"??


It moves the valve - against the return spring - to the mid (both on)
position, but not all the way to the CH-only position. It makes it easier to
fill the system with water by opening both circuits at the same time. If
it's working properly you'll feel quite a lot of resistance from the spring
and gears as you open the valve, and if you then let go of the lever, you
will hear the gears whirring as the spring closes the valve.

Thanks. In the end I'd guessed that it must be the mid-position as I
eventually discovered from info on-line that the spring defaults to "HW
only".

With regard to my faulty valve, I would have thought it would not be
possible to move the override lever if the valve were physically jammed,
but it moved (with resistance, as expected) and also returned with the
spring. Suppose it depends if the physical connection between valve and
actuator can break or slip if the valve jams?

I've cycled the circuit breaker in the fuseboard and I'll see what
happens...

Michael