On Sat, 23 May 2015 15:21:36 +0000 (UTC), HerHusband
wrote:

Ivan,

After running two separate circuits for my daughter's dishwasher and
waste disposal, I was told that I could have simply run a three wire
cable (still 2 breakers) from the panel box and fed the appliances
separately. I understand the concept, but, there would be 2 hot wires
and only one neutral. Would not that neutral carry twice the current
it is designed for?

For that kind of "Edison" circuit, the two breakers must be on opposite
sides of the incoming 240V supply. That way each 120V "hot" leg is out of
phase with the other as the AC cycles back and forth. When one leg is
positive, the other leg is negative. The neutral never has more than a
single load on it.

It's a safe and common way to wire some circuits, but I still prefer to run
separate cables for each circuit. That way breakers can be moved around in
the panel if needed without fear of overloading the cable (if both breakers
were placed on the same phase the neutral would carry twice the load). The
cost difference of two cables vs a three-wire cable is usually minimal for
most homes.

Anthony Watson
www.mountainsoftware.com
www.watsondiy.com
You end up needing to use oversized boxes to handle the wire fill in
many cases, and again, CANADIAN code requires (or at least required in
the past) 2 circuits in the same box to be on a tied breaker or a
pullout fuse block whether they are split/siamesed or totally
separate. If you kill a circuit in a box, you have (in canada) the
assurance that if wired to code, the entire box is deader than a
herring.