In article xA1sd.42$IB6.28@trndny06,
U-CDK_CHARLES\\Charles wrote:
On Fri, 03 Dec 2004 17:35:51 GMT, John Moorhead
wrote:
Nope - I'm in Northern California... Well, I *do* want alternate
circuits... The reason for using a single run of 12/3 is that I wouldn't
have to run an additional separate length of wire - everything would be in
the one cable. Sorry if my post didn't make that clear...

John

I'm reasonably certain that's not allowed in the US.

This wiring method, the so-called "Edison circuit', *is* allowed in at
least some parts of the U.S. No problem with it, anywhere in the greater
metro Chicago area, for example. I recently re-wired my kitchen, in this
-precise- manner, and the city electrical inspector had no problem with
it. He actually wondered 'why so *many* _neutral_ wires?' -- 'cuz I had
outlets on opposite sides of the breaker panel on the _same_ breaker. The
two hot leads were spliced together in a junction box just before the panel
(no splices allowed _in_ the breaker box), but both neutrals ran straight
through to the bar in the breaker box. Simpler than running wire to the
left-side outlet, and then _back_, and over to the right-side outlet.
'Unconventional', but sound engineering, _and_ code-compliant. grin

In any case, the lone neutral lacks the capacity for both circuits.

Bzzzzt!

As long as the two hot legs are on opposite phases of the 240V feed,
the neutral carries only the _difference_ in the two loads. 'Best
case' is that there is -zero- current in the neutral; 'worst case' is
that there is current in the neutral that is the same as -one- of the
hot legs (where the other hot is supporting -zero- load at that time)

Also if it's in a garage, the GFCI will sense the imbalanced current and
trip.

If you use GFCI _outlets_, then there is *no* problem. Speaking from
direct experience here.

To use 'downstream' outlets from a GFCI outlet, you *do* have to have
a 'unique' hot, _and_ a 'unique' neutral, from the GFCI device to the
downstream outlets. You cannot share _that_ wiring across GFCIs.

I'm *not* sure about GFCI _breakers_, having never actually _used_ those
devices. I would _suspect_, however, that they work in the same
manner -- that you can't 'share' the neutral downstream of a GFCI breaker.
"Read the directions" is indicated. grin