Since neutral is normally used to conduct return
current, when used as neutral, there is guaranteed to
be a difference of voltage between neutral and ground,
in the shack. That's the rub, when you don't do
things the NEC way.
Rich, it sounds as if you are simply fortunate. You
have a 240VAC outlet whose neutral is not shared with
other circuits. Since the third wire goes back to the
box, and at the box it is connected to both ground and
neutral, then it is simply a matter of naming whether
you call it "neutral" or "ground".
If, in fact, you have it connected to chassis, and if,
in fact, you are not using it for return current, then
whatever name you have chosen to call it, you are
functionally using it in the NEC definition of
"ground".
If the Heathkit power cord has a green wire, and the
"third" wire in your outlet is green, and you are not
sending return current down it, then you have it wired
as ground - not neutral.
If you are sending return current down that wire, AND
you have it connected to chassis, then you are using
it simultaneously for ground and neutral.
Ohmmeter readings are interesting, but are not the
defining item.
The defining item is what kinds of currents do you use
the wire to carry. If you use the wire to carry
normal return currents, then your usage of the wire is
as a "neutral". If you use the wire to carry fault
currents, then you are using it as a "ground". If you
are using it to carry both, then you are using it as
both neutral and ground, which is possible within the
realm of physics, but there are more fault conditions
that will result in a hazard, than if you used it
differently.
So, being a bit repetitive - it is a neutral or ground
only depending on your usage of the connection. The
color (green for ground, white for neutral) is only
the NEC's ruling on what color should represent what.
A green wire is not ground - a wire that will carry
fault current is ground. It might be green (thus
meeting NEC code) or it might be white (thus violating
NEC code) but it is still ground.
73,
Dave W8NF
--- "R. Measures" <r@somis.org> wrote:
>
>
> >I agree with Dave. I recently wired an SB-221 for
> >240V service. It was wired exactly as Dave
> >describes (third wire is chassis to AC
> >mains safety ground connection). There is no
> >connection between the amplifier and the AC
> >mains neutral.
>
> ** If there is no connection between the two. what
> is the potential
> difference between the neutral and ground?
And the answer is: It doesn't matter! If you're not
using neutral, it can go whichever way it wants, and
the operation and safety of the amp and op are not compromised.
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