Bill wrote:
"Swingman" wrote in message
...
....

Nope ... most 220/240v woodworking tools in North America only need a
total of 3 wires to both work properly and comply with code.



The three wires needed for 220/240v operation a Two hot wires (one from
each hot leg of the service/sub panel), and one ground wire. The ground
wire, while not necessary to power the equipment, is necessary for safety
and code compliance.

Isn't the ground, then, "completing the circuit" in this case?


_NO!!!_

That's what I said earlier and Swing just reiterated -- the ground for a
240V-only motor/appliance/heater/whatever is _purely_ a safety ground.
Remove it and the operation of the device will be totally unaffected.
The only purpose it serves is to ground the case in the event of a fault
that would somehow otherwise energize it.

The circuit is completed between the two legs -- remember, this is AC
and my description of the way in which the voltages are generated as
being tapped from different points on the transformer so one leg is
positive while the other is negative (at the peaks, since the driving
voltage is a sine wave they're both varying continuously but always with
this same 180-degree lag of one relative to the other). Owing to that,
one is always positive with respect to the other (except at the instant
of crossing, of course, and w/ a varying amplitude that is in RMS terms
the 240V) and the current flows from the higher to the lower thru the
device, the direction and magnitude at any time depending on that
varying potential and the load characteristics. Hence the ground in the
240V-only case never sees any current flow at all and can be dispensed
with except for the safety reasons.

The difference is in the split-voltage 120/240V case where there's a
device of both voltages on three-wire service. Then, since the 120V
device _does_ have to have a return, the ground conductor also serves
that role. As noted earlier, that is what the NEC has now outlawed
requiring 4-conductor service to keep the 120V neutral and the safety
ground separate to serve their individual functions.



BTW, I noticed that my outlet on the outside has a single 30 Amp breaker
and that the interior one has a double 50-Amp breaker (s). The 30 Amp one
on the outside
was used by the previously owner for his RV and the interior one for
welding.

My biggest tool will be a 3HP TS which Grizzly suggests a 20 Amp circuit
for. My thought was to
put a Delta 1.5 HP DC on the 30 Amp line and a series of outlets along a
wall that would support
other 220v machinery (including the TS). It seems like the 50-Amp circuit
would support several machines, one-at-a-time,
with the possible future attachment of things like a heater, for example,
later if desired.
....

The 50A service is more than adequate for everything you'll likely ever
have in the shop (other than perhaps if you add a bunch of electric
heat). The rub is, Code won't allow putting a 20A or 30A outlet on a
circuit protected for more than the rating of the outlet (for obvious
reasons if you think about it (and this is one that I _wouldn't_ break
despite my previous comments ) ).

I don't know if you could find 50A standard configuration 240V outlets;
would doubt it. OTOMH, the options I'd see would be

a) Swap the 50A breaker for the rating of outlet(s) you want to use
(Code is happy if conductors are larger than allowed minimums for any
given size breaker),

b) Put in a small subpanel to feed the convenience outlets and wire them
w/ 10g or whatever is appropriate for the chosen feeder breaker for the
subcircuit

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