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From: aalonzo@eagle.wesleyan.edu
Newsgroups: sci.electronics
Subject: Re: What's acceptable voltage ground-neutral?
Message-ID: <1991Apr17.092354.41835@eagle.wesleyan.edu>
Date: 17 Apr 91 14:23:54 GMT
References: <1991Apr13.131621.225@mandata@uunet.uu.net>
Distribution: na
Organization: Wesleyan University
Lines: 28

In article <1991Apr13.131621.225@mandata@uunet.uu.net>, jscott@mandata@uunet.uu.net (Jeff Scott) writes:
> I measured the voltage between the neutral and ground on the outlets
> around my home.  Some read .25 VAC and some read .67 VAC (one or the other,
> nothing inbetween).  Any opinions on whether this is OK?  
> (All this talk about leakage current got me on this in the first place.)

I am not an electrician, but I would expect this voltage to be normal.  It can
be explaned by Ohm's law, and I think there is even a name for it.  I believe
it is called "IR loss".  This name comes from the fact that the voltage you are
measuring is generated by current flowing through the neutral wire, back to the
fuse box.  The neutral wire does have a slight resistance between the fuse box
and the point you are measuring.  The ground wire should be attached to the
nuetral wire in only one place .. the fuse box.  Essentially what you are
measuring is the voltage differance across the length of the nuetral wire of
the particular circut you are testing.  Using Ohm's law, current*resistance =
voltage.  Most home circuts are designed for 15 to 20 amps.  If you take the
measurements you made, and run them through the formula, you could calculate
the aproximate resistance in the neutral wire.  (.67V / 15A = .045 Ohms) 
Actually, .045 Ohms sounds a little low, indicating that less current than 15
Amps was flowing.  Try shutting off the circut breaker for the circut you are
measuring, this will stop all current flowing in the nuetral wire, and thus
should result in a much lower voltage reading.  (0 Volts).

______________________________________________________________________________
Allen Alonzo
Wesleyan University
AALONZO@EAGLE.WESLEYAN.EDU
_______________________________________________________________________________