Potterton Actuator msv322 motorised valve? HELP.......

[Rib Tickler]

My central heating is on even when heating switch is off and only water on. By searching web, i narrowed the problem to the actuator ( potterton msv322. Three port 22mm). The switch on top moves freely. With no change. So i was hoping just to change actuator for new one. I took it off and tried spinning valve by hand. This moves freely with water off, but with water on it won't move. Does this mean the valve is broken as well, or is the valve only meant to move when water stops flowing through it?

 

[ollski]

The spring return on the valve head should hold a wedge inside the valve body covering the ch port when hw only is on...yours doesn't block it off properly so you will almost certainly need to replace the body.

 

[Rib Tickler]

By body, you mean the copper pipe T bit?

 

[corgigazza]

Replace the body complete with new head try honeywell or drayton 3 port valves as these are the best.

 

[ollski]

This bit:

Sorry for size but can't be bothered to edit.