RP wrote in
:


The transformer is located in the air handler. The open end of the
unused blue is probably just touching some sheet metal in the control
section, thus grounding it. It shouldn't be tied in at the t-stat
until it has been confirmed that it's connected to the transformer
common. If the house burns because of your negligence your HO
insurance may not cover it.

Understood.

You're the only one here to inform me that the transformer is in the air
handler. I had the same idea that the wire was grounding out somewhere and
I capped it when I was looking at the heat pump end just to be sure. Since
I was still showing a circuit, I knew there was a connection somewhere
else, but didn't know where.

I ended up getting a non-power stealing stat, so I've managed a work
around. I appreciate the info as it will come in handy if I ever come
across this again.