On Mon, 23 Feb 2009 09:47:10 -0800 (PST), H_X
wrote:

I am working on my son's 100+ year old house, and someone put in a gas
furnace. It works fine.

I am helping him install a new large closet, but when we went to move
an old lighting fixture out of the way, we cam across a bunch of wires
in a box above it. The thing about the wire, is that within the
bundle of white wires, one of the white wires was hot. Again, this
was connected to all the other white wires in the box.

I was suspicious of that wire, so we left it out of the group of other
white wires.

We later on noticed that the furnace was not working.

Shaking my head, I reattached the "hot white" to the other white...and
the furnace went on.

It gets wierder from here.

I am assuming that a qualified electrician wired the house, and made
the black wires hot. There appears to be some evidence of that.
Nevertheless, I am hooking up a socket, and when I did it did not
work. In fact, the White wire is hot on that circuit too. I suspect
the white wire I put back into the mass of wires has electrified the
entire house's white.

Any ideas what the heck is going on?

Thanks.
H
The white wire is "hot" if the furnace is turned on. ALL white wires
are "HOT" when there is a load on the circuit and the white wire is
"open". Just take a look at a circuit.
We'll look at it as a DC circuit for clarity, but AC is the same.

Power comes out of the fuse box on the black wire - it is "Hot". That
black wire goes to a switch. When the switch is off, the second wire
is "cold", when it is on, it is "hot". The black wire continues to the
load - let's say a light. The power flows through the light - so both
sides of the light are "hot" but the light is not on. The white wire
connects to the light and returns to the neutral busss in the fuse
box. If that neutral is "lifted" anywhere wetween the lamp and the
buss, it is "hot".