Re: [CAD_CAM_EDM_DRO] Re: power supply connection issues: COLLECTED WISDOM ON WIRING

I have enjoyed this thread on proper wiring. As a way of helping to make
sure I understand all the issues, I have compiled this document from all
of the recent posts on this subject. This work therefore, is the result
of many posts on this list. Enjoy and be safe! - Eric

WIRING CONNECTIONS -- WHAT DO THE WIRES MEAN AND DO?

N = NEUTRAL CONNECTION (white wire, sometimes called "Common")
The neutral should be connected to your neutral connection in your breaker
box, which is a return line to the transformer. Without it you may get
some strange voltages.

The reason that the white wire is called a neutral instead of a ground is
because that is what it is. It may not necessarily be at ground potential.
It is the ground reference for the transformer but it may not be a ground.
If you have a clamp on amp meter put it on the neutral wire coming from
your house to the transformer on the pole. You will probably get a reading
on the neutral wire. It carries the difference between the 2 hot legs to
your house. If you have 15 amps on one hot leg and 10 amps on the other
hot leg then you will have 5 amps on the neutral. If you are between that
neutral and a better ground than the transformer has that 5 amps will pass
through you to ground. I personally do not want 5 amps of current passing
through me, it is certainly more than enough to cause a 60 cycle heart
failure.

The neutral and the ground wires are not interchangeable.

When wiring a receptacle, The NEUTRAL wire (WHITE) is to be connected to
the SILVER colored screw which connects to the Wider/Higher of the two
blades in the socket.

DO NOT GROUND THE WHITE WIRE AT THE APPLIANCE!! If you do this and reverse
a two prong cord at the outlet or if your outlet is wired incorrectly,
you will end up with a live case !


L = LINE VOLTAGE (black wire, sometimes called "Hot")

When wiring a receptacle, The LINE (HOT) wire (BLACK) is to be connected
to the BRASS colored screw which connects to the Narrower/Shorter of the
two blades in the socket. NOTE: LINE Can legally be any color but white.
{Exception} being if it is a switched receptacle and it is a white feeding
from the switch, but it should be marked with black tape.

G = GROUND (green wire in USA and Green w/ yellow stripe in Europe)
The green case ground should go to a good hard ground, such as a driven
ground rod.

The Ground wire does not "normally" conduct any current. It is present
for "safety". If there is a "short circuit" in the machinery from "L"
(aka "hot") to the chassis, etc., this Green wire, then, conducts this
current to GROUND, [hopefully-] blowing the breaker or fuze. Oh, it might
also serve to "drain" EMI nasties, but not really much "measurable"
current would be involved in that.

You can hook the Ground (Green) wire to a water pipe also, anything that
is well grounded. It is called a case ground for a good reason, it grounds
the case of the equipment. If there is a short to the case of the
equipment it takes it to ground instead of to you the first time that you
touch (it. People used to get killed that way, that is why there is a 3
wire system now instead of the old 2 wire system.)

You pays your money and you takes your chances as they say, to you it may
not be worth the effort of running a ground wire, to me it would be a no
brainer. I've been doing Power Co work for over 40 years, I expect to
retire next year with no burn marks on me after working with everything
from 110 volts to 34500 volts on a daily basis.

Personally, I'd rely more on getting the green wire back to the fuse box
and connecting it to the neutral/ground buss bar. From
there, you should have a connection to either a water pipe (be sure to put
a bypass wire around the meter) or to a good earth ground.

When wiring a receptacle, The GROUND wire (GREEN) is to be connected to
the screw with the GREEN tab, which connects to the round connector below
the Neutral and Line blades of the socket.

The neutral and the ground wires are not interchangeable.

NEVER fail to USE the GROUND WIRE properly!

GROUND RODS
There is a safety concern with machinery having large expanses of metal to
lay your hand on. A ground rod separate from the rest of the electrical
system is 'illegal', as the rod may or may not make good contact with
conductive earth.

GROUND FAULT CIRCUIT INTERRUPTER (GFI)
GFI Equipped wiring has a "Ground Fault Circuit Interruptor", usually a
strange-looking duplex-outlet with a couple of
funny push-buttons between 'em, in the "main bath", where one plugs in
electric shavers and/or hair-dryers. THAT "GFI" has an ELECTRONIC sensor
built into it which COMPARES the current ("amperage") flowing IN via the
"hot" or "L", to that flowing OUT via the "N" Neutral, back to the
[ground] in the electrical panel box where all the "breakers" are. If a
VERY FEW milliamperes more current flows IN than flows OUT, it means SOME
of the current is "escaping" "outside the circuit", such as when you drop
your dryer in the bathtub and kill the child therein, etc. The GFI then
instantly OPENS the circuit (as does a current overload which would blow
the fuze), and this (hopefully) saves the child in the bathtub who pulled
his AC-powered radio into the bath, while attempting to change the hip-hop
station.

There IS a reason for that "green wire", and, while most appliances WILL
operate if it is not connected, doing so is VERY DANGEROUS and "19th
Century mentality."

Further: GROUNDING the "box" or "chassis" of your appliance (or the metal
body of your hand-held power-drill, etc.!) will certainly NOT "smoke" your
just-purchased toy, but may-well SAVE YOUR LIFE!!!!

If your electrical outlets have only TWO conductors to each outlet, you do
not have this protection.


More on Grounding:
A power supply will almost certainly work without the ground, but if there
is a malfunction that bridges the insulation of the power supply, you
could get zapped. I tend to be pretty cavalier about a lot of stuff, but
at least when I get stuff permanently installed, I make sure the safety
grounds are properly done. Don't trust a separate ground rod, because
when a real short develops, it may have to sink hundreds of amps until the
breaker blows, and if you are touching the machine at the time, you'll get
the voltage drop across your body. Only a solid metal conductor running
all the way back to the transformer neutral can guarantee that such a voltage drop will be
small.

How to test for ground on an appliance: You should be able to see if G is
ground just by what it is connected to and the trace routing. Usually,
the ground is connected to the outside case so it you get zero resistance
between G and the case, that should be that.

If it is AC input, it really won't matter which goes where. If it has a
switch on it, generally the black wire coming from the wall socket is
switched and the white is common. Again, the white should be the N or
neutral, and L the black or Live. But just in case, see if the L goes
thru the switch (if any) and that should say something.

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