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Sparks...
(Not an electrician)
"Roger" wrote in message
k...
The message
from The Natural Philosopher contains these words:

That alone won't give rise to the symptoms you describe. If the
system has
been wired properly, then the controller overides any other auxiliary
switches (like the thermostat, the aux switches on the valves) in the
circuit.

I don't think that follows. Surely the microswitch on the valve is fed
from the permanent live and the controller provides a switched live for
the thermostat. (That is certainly the way my controller should be
wired).

It's wired from permanent live on the switched fused spur that should
run the whole heating system..

How come? The microswitch only closes when the thermostat powers up the
actuator.

Unless the actuator is faulty, has stuck on, one side of the microsowitch is
connected to the boiler, and the other is connected to a permanant live - I
am guessing the feed to the valve switch should be connected to the output
from the thermostat, and the other side of the thermostat is connected to
the output of the programmer?

Sparks...