In an earlier contribution to this discussion,
Ian Cornish" "icornish at talk21 dot com "icornish at talk21 dot com"
wrote:

Apologies for probably not using the right technical terms...I'm not a
plumber.

However, I appear to be having issues with the motorised valve thingy
on my heating system. Before calling out a plumber, I'd like to
know more about it, and likely causes of problems.
The problem is that it switches from heating to hot water OK, but no
matter what I try, it will not switch from HW to heating
automatically - I have to use the little lever on it to move it back.

Is this a wiring issue, or just a knackered valve ?

TIA,

Ian

Has it *ever* worked properly? If so, it's probably a dicky motor in the
actuator - which is supposed to motor the valve from the HW-only through the
HW+CH position to the CH-only position. The motor only works in one
direction - the return being provided by a spring.

[If it's *never* worked, it could be wired wrongly. Have a look at the
Y-Plan wiring in http://content.honeywell.com/uk/homes/systems.htm ]

In many cases, you can remove the actuator (the electrical bit) from the top
of the valve, revealing a spindle with a flat bit on it. You should be able
to rotate the spindle through 90 degrees from the HW to the CH position
without too much effort. It *could* be seized, but your problem is most
likely to be the actuator. You can replace the actuator without needing to
drain the wet part of the system - but pay particular attention to the
wiring, and connect the new one up exactly the same.
--
Cheers,
Set Square
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