Not all zone valves are spring loaded to close.
Some valves use a spdt TS that sends power to the valve to open AND sends power to the valve to close it.
Sorry I thought the discussion was about "water valves, not forced air air duct zone valves.
I should have read the original post better and/or remained a lurker.
[This message has been edited by SparksNmore (edited 12-03-2005).]