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.
{edit}
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.
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[This message has been edited by SparksNmore (edited 12-03-2005).]
