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(Carl) wrote in
om:

Hi all, I am deperate for some help - my controller for my CH and HW
was damaged during some building works. I have bought an identical
controller and fitted exactly as it was but it will only turn on the
boiler for HW.

If I bypass the controller and connect the HW wire and CH wire to the
live - I have both HW and CH fine. But if I connect just the CH to
the live I get nothing??

Any help - I am stuck here!!!

Thanks in advance!

Sounds like a problem with the 3 port valve, if that's what you've got.

When the HW cylinder stat calls for heat, the boiler and pump are
started, as the 3port valve defaults to leave the HW circuit open but
when the room stat calls for heat, the boiler and pump are not started
until the valve has actually diverted to open the CH circuit to the
rads. It's done by the microswitch that is operated at the end of the
valve's travel.

This stops the boiler and pump trying to work into a closed circuit if
the valve breaks.

You may also, if it's accessible, be able to change just the valve's
electric motor; me, I'd buy a new actuator.

You may be able to remove the electric bit from the valve, check that
the valve itself is not seized solid, and replace the motor section,
without disturbing anything wet.

If it's an old valve, (like mine was ;-( ) you'll have to replace the
whole thing - the good news is that they're pretty well interchangeable.

HTH

mike