Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cwjcc!gatech!emory!stiatl!john
From: john@stiatl.UUCP (John DeArmond)
Newsgroups: sci.electronics
Subject: Re: How can I recognize true ground?
Message-ID: <5730@stiatl.UUCP>
Date: 13 Jul 89 00:58:34 GMT
References: <18425@mimsy.UUCP> <1547@unccvax.UUCP> <3283@kitty.UUCP> <5651@stiatl.UUCP> <178@zip.eecs.umich.edu>
Reply-To: john@stiatl.UUCP (John DeArmond)
Organization: Sales Technologies Inc., "The Procedure IS the product"
Lines: 38

In article <178@zip.eecs.umich.edu> don@zip.eecs.umich.edu.UUCP (Don Winsor) writes:
>
>I've run into a poor wiring job in an older house belonging to
>friends where I found a multitude of sins.  One of them was that
>some grounded receptacles were wired with old two conductor cable
>and they just had the neutral and ground pins tied together at
>the receptacles.  In the interests of safety I suggested they
>pull modern NM cable to these receptacles, which didn't seem too
>hard to do, since there was easy access down through the wall and
>into the (unfinished) basement.  My friend didn't think this was
>necessary, and I couldn't come up with a good, convincing argument
>that this was a bad idea.  His line of reasoning was that the
>ground and neutral wires all went to the same bus bar on the
>main breaker panel, so running another conductor offered no
>advantage.  Can anyone offer a good, clear, convincing argument
>to refute this?  

YES, I can.  The neutral wire has a finite resistance.  At full load,
even a good connection will drop a few volts.  These few volts would
be imposed on the frame of your "grounded" appliance.  Even if this
voltage is not enough to shock you, it could be enough to damage 
sensitive electronics or cause electrolytic damage if the device becomes
wet.

And, of course, if the neutral wire ever corrodes, you get zapped.

A last consideration is that if your house ever caught on fire and
electrical problems were indicated as a cause, the insurance company
could try to use the code violations as an excuse not to pay.  they
may not be successful but is it worth the chance?

John


-- 
John De Armond, WD4OQC                     | Manual? ... What manual ?!? 
Sales Technologies, Inc.    Atlanta, GA    | This is Unix, My son, You 
...!gatech!stiatl!john    **I am the NRA** | just GOTTA Know!!!