Roy Smith wrote:
I don't know much about the NEC, but I do understand polyphase
circuits (4 years of EE in college). I don't think I've ever heard
the term J-factor. What is it?

The "J" factor is the square root of -1. No, really.
it is mainly used for plotting how voltage/current leads/lags
current/voltage in inductive or capacitive circuits. I am no
electrical/electronic engineer, just a simple tech with enough knowledge
to know that everyone's argument is "a little" right.

The 2 110vAC "phases" that come into your home are 180deg "out of phase"
with respect to one another as a simple product of the physics of the
windings (secondary) of a transformer. You could, in fact, produce a
transformer where the 2 legs are in phase, but that would only go so far
until the "electrical lengths" of the 2 legs become different.

Two true phases of electricity deal with the physical location of the
wires as they come from the generator, and their phase relationship is
relative to their respective location. If you have a generator, and you
place 3 "brushes" equidistant around the amature, those 3 "phases" will
be 120deg "out of phase" with each of their neighbors. if you increase
the brushes to four, and place them equidistant, each will be 90deg out
of phase to its neighbor, and 180deg out of phase with its diametric
opposite cousin. Take any number, place it around the armature, divide
by 360, and you will get the phase relationship between any 2 legs. see

http://www.tpub.com/content/neets/14.../14177_67.html

take a look @ fig. "B". on the right side of the figure, you see the
three windings labelled "7". Those are 120deg out of phase with one
another.

Since, I believe, the original question was about wiring 110 and 220 on
the same circuit, and the dryer/oven timer wiring was mentioned,
remember that the 220 is stepped down to 110 usually as a
convenience(because the 110 is readily available, existing only to
become one of the additives for 220 when necessary to perform the
primary function of the device; i.e. the heating element), and is tapped
off of in parallel to run the power supply of the "convenience"
items(clock, timer, motor) at a much more friendly voltage-5 or 12vDC in
the case of the newer appliances.

The simple answer to the question is yes. 110 and 220 co-exist quite
nicely in a circuit. If you try to make up a home-brewed solution to
allow them to co-exist, it would be a good idea to get advice not from a
newsgroup, or the web itself. Consulting with a live electrician, an
electrical inspector, AND your homeowner's insurance carrier is a must!
Insurance will not cover incidents caused by wiring not done to code.
DAMHIKT!