"Charlie" wrote in message
...
Okay, I went back and checked the original connections... again.
As I described it, there was no return path, and hooking it all up
proved it - nothing worked.

So, the ground at the vent is not floating, it is tied to the return.
Near as I can tell, it's a cheap way of avoiding another run to the
hardware store for some 3-wire or another run. Am I looking at a
short-cut?

cg

Not a shortcut, a non professional, dangerous mess. Get a piece of 14/3 with
ground and wire it correctly