Sorry...neglected to answer your original question. I believe the NEC
frowns on connecting across one phase of a 230V circuit to get 115V. That
WOULD double the current on the neutral and result in a potential overload.

"Chuck Hoffman" wrote in message
...
There is no argument at all. In a two-wire 115V circuit, the current
carried by the neutral is exactly the same as that carried by the hot
wire.
In a three-wire 230V circuit, there is a property called phase angle or
J-factor. This results in current flowing in both directions at the same
time (this is not exactly a true statement but a convenient way to
consider
current flow in a three-wire circuit). As the current on one phase
increases from zero to some positive value, the current in the other phase
is decreasing from its positive value to zero. The vector sum of the
currents on the neutral is exactly the same as the total of both phases.
Because of the phase angle, however, that does not mean twice the current.
It never exceeds the total current of each phase individually.

Confusing? Yes. One has to study alternating current and understand
plane
geometry and simple trigonometry to comprehend it.

"Keith Carlson" wrote in message
news:%zEyd.245829$V41.11293@attbi_s52...
I know I'm going to get the "DAGS" for this question, but I just came
from
there, and I didn't see this specific information. Lots of debate about
how
much current the neutral wire carries, though :-)

With a 3-wire circuit, is it okay to wire both 120V and 240V outlets on
that
same circuit? I know it's *possible* by using the two hots for 240 and
either hot and neutral for 120, but is it recommended? Maybe this is
the
main reason for this type of circuit, so I didn't see reference to it on
Google. Much of the discussion I read was on balancing the load, which
could
imply using the 3-wire circuit with all 120V outlets.

I've got a dust collector coming soon, and the extra 6-7 continuous amps
is
going to result in some frequent breaker trips when I start a saw or
planer.
Looked at my electrical service, and found there's an unused double-pole
30A
breaker, feeding an unused dryer outlet (house had a gas dryer when I
moved
in). That should give me the 2 hots for a 3-wire circuit.

My thought on this type of circuit is to wire one outlet at 240V
(re-wire
DC
motor to 220V), and the rest wired at 120V. With that 30A breaker and 10
AWG
wire, should have no problem handling the loads from a DC and air
cleaner
running, and startup surge from another tool.

An electrician would be a good idea, too. Hopefully I can find someone
willing to consult with me; I can do the wiring myself.
But I'm hoping to get some idea if this is the way I want to go so I can
cost materials. Won't get an electrician or the inspector on the phone
until next week.

TIA