Mid Position Valve (Drayton)?

Hi,

My problem is with my central heating and hot water system. This is a long one!

When I select just hot water, some of the radiators get hot. I removed (from the valve) and looked at the mid postion actuator and this is what I found: -

When Heating selected (and the room thermostat on full) the dial on the acutator would move (to the right) to the "H" and the "key-way" (which would turn the valve spindle) would turn right 45deg (as i'm looking at it). When both heating and water was selected the dial would move to the "M" and the "key-way" would turn left to 0deg (key-way vertical), but when i select just water the dial moves to the "W" and the "Key-way" stays in the 0deg postion. My thinking was that this should turn -45deg left. So thinking that the actuator was faulty, I but a spanner on the valve spindle to turn it manually so that just water was on and the spindle snapped. This left me with no heating but with hot water.

A plumber/ heating enginneer was called out he replaced the valve, but not the actuator. Heating now back on but still the orginal problem. Hot water on only and some radiators on too.

So the questions are-

Should the, and can you move the valve spindle manually left, for hot water, straight up, for both and right for heating, if so does the system need to be off before turning the valve?

Also should you be able to turn the valve with your fingers?

And when looking at the "key-way" should that turn -45 deg left, indicating water only?

As i see it when i select just hot water the indicater is moving to the "W" postion but the "key-way" is only moving to the 0deg postion (straight up) meaning both hot water and heating coming on (i've had the actuator apart and it appears to be working as designed- when hot water req, motor is de-energized the springs return the key way to original state which appears so be straight up, or am i missing something simple)

Any advice to help me understand is greatly appreciated.

Eddie
January 2012