3 port diverter valve - is this correct?

Should not be a problem - it means the heating circuit will have a bigger share of the available flow from the pump.

No

All the valves I've seen move through 90 degrees from HW to CH - with the mid-position being at 45 degrees.

Sounds like someone has designed an 'improvement' into yours which gives a bit more flow to the CH than to the HW when both are demanded at the same time. I doubt whether it's a fault - it actually sounds like quite a good idea.

Did it come with a leaflet which describes its operation? If so, what does

Unfortunately the instruction leaflet is rather vague and just has the wiring diagram and port positions. Can't find it on the web either the box says Landis & Staefa but the valve itself is branded Siemens. Model no appears to be MA-V322C. Think I'll just give it a try, should soon be apparent if the HW is starved of flow.

Landis & Staefa is now part of Siemens Building Technologies, and not too easy to find. There is what might be a similar model to yours here; CMV? 22 and 28mm 3-port motorised valves.

Phil

The literature refers to a 'wedge' type actuator. Anyone know what that means?

Where did you find that literature Roger? I couldn't find anything further on that site. Mark says of his "its like a rubber wedge".

Phil

Phil The uk.d-i-y FAQ is at

I was referring to the second reference which you gave. If you click on the Flow Control bit, it shows pictures of 2 and 3 port valves, with a list of features. 'Wedge type adtuator' is one of the features listed.

Ahh, right. Saw those... just glanced and went looking for the detailed download - nowt there!! Siemens have seriously dumbed down the old Landis & Gyr/Staefa site.

Phil