Hi all
My heating system has two Landis and Gyr 2-way spring-return motorised valves (Landis and Gyr ZA-V222). The one for the hot water cylinder gets stuck in the open position, so even if the mains power to the system is turned off, the spring does not return the valve to the closed position. It first did this on one occasion two weeks ago, but since then has been working fine until yesterday. Now it sticks every time. I removed the synchronous motor and found that I can manually return the valve to the closed position by rotating the toothed plate (which normally meshes with the cog on the synchronous motor) but it needs a quite a lot of force. If I then use the spring-loaded "manual override" lever to move the valve towards the open position, the return spring does not have enough strength to pull the mechanism back towards the closed position.
Are there any tricks to free up a jammed motorised valve, or do I need to replace it?
thanks
Julian