In article , Philip Lewis wrote:

A 240 line is usually the neutral and the two hot phases of the 120V
service in the residential home. (sometimes they have ground as well)

Not correct. A 240V circuit is usually the *ground* and the two hot legs of
the *240V* service in the home. Sometimes they have *neutral* as well.

240V circuits that do not need to supply 120V loads (a water heater supply is
an example of such a circuit) generally do *not* have a neutral, because they
don't need it.

Normally, the neutral is present *only* in 240V circuits that need to supply
120V loads as well, e.g. an electric oven (heating elements are 240V,
timer and light are 120V), or an electric dryer (heating elements are 240V,
motor probably 120V, timer definitely 120V) -- and only then if the circuit
was wired fairly recently. Code *used* to permit using the grounding conductor
as the neutral, which isn't really especially safe. It's no longer allowed,
but there are a *lot* of dryer and range circuits in existence that don't have
a neutral conductor.

If *I* needed a temporary 120V feed, I'd get a 240V (dryer) cord, run
it into a outlet box, cap one of the hot feeds, and wire up the second
hot/neutral to an outlet.

And by doing so, you'd probably create a dangerous condition, because that
240V circuit probably doesn't have a neutral, and you'd be using the equipment
grounding conductor as the neutral.

I'd really want to put some sort of ground
on the device if possible, or use a gfci outlet if ground wasn't
available. Then I would plug in only when using the feed. This would
probably break all sorts of rules in the NEC though... so I wouldn't
recommend it for someone else.

If *I* were doing that, I'd make sure I had a neutral first. I'd also make
sure I understood the Code, and *why* it disallows some practices.

I'm not a licensed electrician

I can tell. You should not be giving out electrical advice, until you
understand the difference between neutral and ground, and how 240V circuits
are configured.

--
Regards,
Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt.
And who wants to leave buttprints in the sands of time?