Xref: utzoo misc.consumers:4908 misc.consumers.house:2232 sci.electronics:2951
Path: utzoo!attcan!uunet!seismo!sundc!pitstop!sun!decwrl!labrea!glacier!jbn
From: jbn@glacier.STANFORD.EDU (John B. Nagle)
Newsgroups: misc.consumers,misc.consumers.house,sci.electronics
Subject: Re: the truth about GFCI's
Keywords: GFCI, RFI, noise
Message-ID: <17444@glacier.STANFORD.EDU>
Date: 12 May 88 16:00:56 GMT
References: <2005@hou2d.UUCP>
Reply-To: jbn@glacier.UUCP (John B. Nagle)
Distribution: na
Organization: Stanford University
Lines: 19


      We've now established that one cannot entirely rely on the protective
ground pin as a path to ground.  The GFCI handles the safety aspect, but
what about the use of protective ground as part of shielding in electronic
equipment?  Open grounds can cause hum, noise, and weak reception of RF signals.
They also can eliminate one of the defenses of electronic equipment vulnerable
to static charges.  When you walk across the carpet and build up a big static
charge, then touch your computer, where does the charge go?  

      Ungrounded GFCIs are rare, fortunately.  But it is worth thinking about
this if, say, you had a GFCI outlet installed in a house with older wiring
because you needed a 3-prong outlet for a computer.  It is probably not a
good thing to plug elaborate electronics with interconnects to other units,
such as computers and sound systems, into such an outlet.  On many such
units, logic ground is tied to protective ground and the cabinet, so
an ungrounded outlet results in a direct connection from the case and
cables to the system's ground reference.

					John Nagle