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GFCI operation question Methos 08-24-2006
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Posted by Methos on August 24, 2006, 9:59 pm

the way a GFCI functions, would it trip
if a bad connection were made to it ?

(if say, a terminal with the hot or
neutral wasn't screwed down tight &
a plugged in load drew current causing
the terminal to warm up - would the
GFCI trip ?)



Posted by Jonny on August 24, 2006, 10:28 pm
http://ts.nist.gov/ts/htdocs/210/gsig/apec-elec/gannon.ppt

The load's current use is sensed by the GFCI whether wired dubiously as in
the example you imposed.

The problem child is when the grounding and neutral are swapped.

Arcing, as implied by your example, needs an AFI circuit for detection.
--
Jonny
>
> the way a GFCI functions, would it trip
> if a bad connection were made to it ?
>
> (if say, a terminal with the hot or
> neutral wasn't screwed down tight &
> a plugged in load drew current causing
> the terminal to warm up - would the
> GFCI trip ?)
>
>



Posted by Methos on August 25, 2006, 8:38 am

> http://ts.nist.gov/ts/htdocs/210/gsig/apec-elec/gannon.ppt
>
> The load's current use is sensed by the GFCI whether wired dubiously as in
> the example you imposed.
>
> The problem child is when the grounding and neutral are swapped.
>
> Arcing, as implied by your example, needs an AFI circuit for detection.
> --
> Jonny
> >
> > the way a GFCI functions, would it trip
> > if a bad connection were made to it ?
> >
> > (if say, a terminal with the hot or
> > neutral wasn't screwed down tight &
> > a plugged in load drew current causing
> > the terminal to warm up - would the
> > GFCI trip ?)
> >
> >

thanks everyone for the responses.

the powerpoint link was very informative.

if i understood it correctly, any current differential
> 5ma between hot & neutral would cause a trip.

if one terminal has contact resistance (loose),
wouldn't the current flow on that leg be reduced
by the amount of resistance ? and therefore trip
the GFCI ? (since it would see less on one leg,
vs the other - or am I misinterpreting, since a
hot/load/neutral circuit is basically in series,
and current is only depended on how much the
device draws?)




Posted by mm on August 24, 2006, 11:14 pm
On Thu, 24 Aug 2006 21:59:15 -0400, "Methos"

>
>the way a GFCI functions, would it trip
>if a bad connection were made to it ?
>
>(if say, a terminal with the hot or
> neutral wasn't screwed down tight &
> a plugged in load drew current causing
> the terminal to warm up - would the
> GFCI trip ?)

I don't think so. Why would the resistance of a bad connection be any
different from the resistance of a light bulb.

I wouldn't assume there will be arcing just because a connection isn't
tight enough. So I wouldn't assume that even an arc fault circuit
breaker would be tripped by a loose connection. Am I right or wrong?


Posted by LightsAREon on August 24, 2006, 11:25 pm
mm wrote:
> On Thu, 24 Aug 2006 21:59:15 -0400, "Methos"
>
>> the way a GFCI functions, would it trip
>> if a bad connection were made to it ?
>>
>> (if say, a terminal with the hot or
>> neutral wasn't screwed down tight &
>> a plugged in load drew current causing
>> the terminal to warm up - would the
>> GFCI trip ?)
>
> I don't think so. Why would the resistance of a bad connection be any
> different from the resistance of a light bulb.
>
> I wouldn't assume there will be arcing just because a connection isn't
> tight enough. So I wouldn't assume that even an arc fault circuit
> breaker would be tripped by a loose connection. Am I right or wrong?
>


Methos

A GFIC is made to trip on sudden line voltage changes. A slow warm up
would not trip the built in breaker. This very problem cause a house
fire that burned a third of my parents house to the ground. Two wires
in some old Romex touched and caused a slow short but it was not enough
to trip the breakers. Therefore, it warmed up long enough to catch fire.

GFIC's are a nice safety feature but it certainly doesn't catch all problems

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