no hot water, heating won't go off

[MattWills]

Friend of mine has a Baxi back boiler, hot water cylinder, and 3-port valve (not sure if diverter or mid-position until I see it, though guessing mid-position).

She says that she stopped getting hot water yesterday, and the heating won't go off when she turns the programmer to CH off. I'm guessing the motorized valve has probably seized in CH position. Sorry I don't have any more details about the system at the moment, but does that sound like a reasonable assumption?

If the valve has seized, does it make sense to change the whole valve rather than just the actuator?

Thanks in anticipation!

 

[mogget]

Sounds about right.

If the valve has a replaceable head, I would buy a complete valve and first try swapping just the head. If that didn't work I'd drain down and change the valve body (reuniting it with it's actuator).

The pro's on here may see it a different way of course.

 

[gas4you]

Does sound like the 3 port jammed on ch, but before changing it a simple check that the programmer is working correctly and that the valve is not getting a permanent live feed to the ch wire.

 

[seco services]

if the valve was seized in ch position and ch is turned off at programmer and hw is still calling for heat the water will take the ch route through the valve as its seized in ch.
or if the hw is off at programmer or satisfied it will still run as the grey wire will be live and the valve is ativating the micro switch giving power to the boiler etc.

if you isolate the mains power to the whole system the valve should fall to its relaxed position.
giving resistance on the lever on the end of the valve.
if the lever is floppy then the valve is still in ch only position.

 

[MattWills]

Thanks all, that's really helpful.