On Sun, 28 Dec 2003 04:31:31 GMT, "Ivan Vegvary"
wrote:

Getting things arranged in my new (new for me) shop. It has 3 phase power,
therefore the questions.

1) Do I simply run 3 wires to the machines (lathe, mill, grinder & surface
grinder) and let the conduit be the ground, or do I need a seperate ground
wire. The existing building has a few 3ph outlets (in conduit), but no
ground wires.

That used to meet the rules, but all new work should have a ground
wire run inside with the rest of the conductors, and you should
retrofit everything old that you work on as a safety matter. One
loose conduit fitting anywhere in the run (and it happens a lot) and
all your equipment isn't grounded anymore. On heavier circuits you
can use a reduced size ground, like #8 hots with a #10 ground, as long
as the ground wire gauge is heavy enough to pop the breaker on a short
circuit without damage.

If you have 240V 3-phase Open Delta "High Leg" power (two lines are
120V to ground but one line is 208V to ground) make sure to code the
High Leg with Orange wire and tapes, and be very careful not to hook
it to the control circuits of the equipment. Or to 120V loads, where
the "Magic Smoke" will escape from any device plugged in...

And if the machine takes 120V from one of those legs to ground for
the work lights or control circuits, you need to run a white neutral
wire in the conduit, too. It used to be legal to put parasitic loads
like that on the safety ground wire, but no more.

2) My machines will be out in the middle of the floor. Do I simply dangle a
conduit from the roof framing (15 ft. above), or, do I install a post upon
which the conduit will come down? Do I do this once for each machine?
Somebody must have a clever solution to this situation. I don't want to cut
up my slab and install wires below.

You can drop it from the ceiling, but you should have a vertical 2x4
there for support of the conduit - and that will also give you a place
to mount the safety switch & receptacle. You always need a way to
lock-out a piece of gear while you're working on it, and a fused
safety switch mounted within easy reach of the machine operator is the
safest way for hard-wired tools.

You could use cord drops from the ceiling, but you need to hang them
from strain relief cord grips, the wire basket "chinese handcuff"
style, or they'll pull out of the fittings from their own weight. If
you use a cord cap as the disconnect & lockout device, you'll need to
buy or build the little locking metal plug boxes that physically
enclose the machine's plug to prevent the cord being plugged in.

For the final word on how it needs to be done, call up your local
Building Inspection authority (city, county, state depending on where
you are) and have a "Hypothetical" discussion with them about how it
should be done in their area to satisfy the codes "if you were going
to do it." (Wink, nod...) They may let it slide without an inspection
(and the necessary plans, permits & fees) but you still want to do the
work right.

Don't poo-pooh locking stuff out - ALWAYS as a bare minimum at least
tag (paper note "Leave Circuit 3 Off! Working on lathe.") and tape
the breaker to the OFF position as a clue for the uninitiated. If you
have children (or employees), they sell lock adapters for most modern
breaker panels that clamp the breaker handle in the OFF position.

The first time someone turns the power back on could be deadly -
somebody pops another circuit, doesn't call you, and just goes to the
main panel and starts cycling all the breakers back on. While you're
out in the shop and have your arms inside the machine up to your
elbows...

Or worse, you forget that you weren't done with the repairs and you
turn the breaker back on & blow it up yourself...

-- Bruce --