Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!phri!roy
From: roy@phri.UUCP (Roy Smith)
Newsgroups: sci.electronics
Subject: Re: Re: How can I recognize true ground?
Message-ID: <3869@phri.UUCP>
Date: 16 Jul 89 15:00:58 GMT
References: <1989Jul7.155721.19105@utzoo.uucp> <11170023@hpfcdj.HP.COM>
Reply-To: roy@phri.UUCP (Roy Smith)
Organization: Public Health Research Inst. (NY, NY)
Lines: 23

In article <11170023@hpfcdj.HP.COM> myers@hpfcdj.HP.COM (Bob Myers) writes:
> That's the beauty of a GFI over the panel breakers, which can't tell whether
> the current returns via neutral or ground (or someplace else), and will
> happily permit current up to their trip point to pass through your body.)

	This is not to say that a GFI is the be-all and end-all when it comes
to protection.  Imagine the (admittedly rare) case of shorting the hot wire
directly to the neutral.  You'll get a perfectly balanced short (well, from
the point of view of a power engineer, it's an unbalanced phase-to-neutral
fault, but from the point of view of your GFI it's balanced).  Your GFI will
be perfectly happy to keep the circuit open until the wire melt if it didn't
have a conventional breaker to back it up.

	Don't think it doesn't happen.  Imagine a kid, looking remarkably like
I did when I was about 11 years old, putting two screwdrivers into the wall
outlet and laying a third screwdriver across the top.  BOOM!  Hey, how come
all the lights went out?  Sometimes I wonder how I stayed alive long enough to
understand the crazy things I did as a kid.
-- 
Roy Smith, Public Health Research Institute
455 First Avenue, New York, NY 10016
{att,philabs,cmcl2,rutgers,hombre}!phri!roy -or- roy@alanine.phri.nyu.edu
"The connector is the network"