On Fri, 12 Nov 2004 20:25:20 -0500 "Rodney Kelp"
wrote:

If you look inside some power panels the white neutral is connected to the
same terminal block as the green ground wires.
What's the diff?

The connection between ground and neutral is made at exactly one
place, and that place is generally where the power comes into the
house, the service entrance.

After that point the ground and the neutral travel out to the rest of
the house to all the outlets that you have. The ground normally
carries no current, so there is no voltage drop between any point on
it and the actual ground at the service entrance.

The neutral carries current, so there will always be some voltage on
the neutral conductor. That voltage will depend on the distance from
the service entrance ground, the size of the conductor, and the amount
of return current being carried by the neutral. The voltage on the
neutral is usually less than 1 V, but it can be as much as 3-4 volts
in large installations with large currents.

While 3-4 volts would not be much of a safety hazard, think what would
happen if there was a problem with the neutral conductor somewhere
between your outlet and the service entrance. The voltage on the
neutral conductor would jump up to the line voltage. If you have
"grounded" your appliance to the neutral, then the external metal
parts of your appliance are now at line voltage.

For this reason, the code requires that the ground wire must not carry
any current except under fault conditions, and it also requires that
you not use the neutral to "ground" anything.

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Jim Adney
Madison, WI 53711 USA
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