Date:         Tue, 13 May 1997 12:05:50 -0400
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         "Rodney L. Boleyn" <boleyn@scr.siemens.com>
Subject:      Re: Neat Camper upgrade


"James R. Wetzel" <jrwetz@sunlink.net> wrote:
>RubatoGuy@aol.com wrote:
>> 
>> Ron asked:
>> >What *is* a GIFI outlet?
>> 
>> Ground Fault Interuption Circuit (GIFC) Opps, looks like I did the accronym
>> wrong.
>>
>It is really GFCI or ground fault circuit interrupter.  They can kill
>power in 1/40th of a second and will "Trip" if there are slight current
>changes (Or a big one).  Excellent idea.

Closer, but I still don't think this is an accurate description.  In a
3-wire household electrical system, the hot wire and the neutral wire
are the normal source and sink of the electricity (since it's A/C,
they take turns as source and sink of current).  The ground wire hangs
around as a protective path to ground, and it's usually used for
grounding appliance housings and such.  The ground wire is not
actually *in* the path of the electricity flow at all.

Now, your household circuit breakers detect over-currents through the
hot and neutral wires.  The only way a panel breaker trips on a ground
fault is if the fault drains enough current through the hot wire to
throw the breaker, and then only because the over-current is being
supplied by the hot wire, not because it's being drained to ground.

But the point of a GFCI outlet is, NO current is ever really supposed
to drain to ground.  Even a few milliamps to ground could signal that
something is wrong.  A 20A circuit breaker isn't going to notice when
a 5A appliance suddenly starts drawing 5.03A and draining 30mA of it
to ground.  The GFCI outlets have sensors in them that detect even
very small currents going down the *ground* wire, and trip the
internal breaker regardless of what's going on with the hot and
neutral wires.

-Rodney