# GFCI operation question

Page 1 of 3
• posted on August 25, 2006, 1:59 am
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 ?)

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 25, 2006, 2:28 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
"Methos" < snipped-for-privacy@Lochschiel.nospam.com> wrote in message

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 25, 2006, 12:38 pm

thanks everyone for the responses.
the powerpoint link was very informative.
if i understood it correctly, any current differential

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?)

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 25, 2006, 12:46 pm

Both wires are part of the same series circuit and the current will be the same whileever there is no other path (ground).
Current in = current out.
The resistance of the contact will be part of the impedance (along with the real load) that determines the magnitude of the current.
--
John G

Wot\'s Your Real Problem?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 25, 2006, 3:14 am
On Thu, 24 Aug 2006 21:59:15 -0400, "Methos"

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?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 25, 2006, 3:25 am
mm wrote:

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

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 26, 2006, 7:11 am
LightsAREon wrote:

I agree with others that a GFCi wouldn't trip on a loose connection.

A loose connection can produce enough heat to start a fire without arcing (a "glowing" connection). Late stages in failure are likely to arc.
AFCIs sense "parallel" arcs - from hot-to-neutral (a "fault", the F in AFCI). Starting in 2008 the NEC requires them to also detect "series" arcs, as in a loose connection. As far as I know, no current AFCIs detect series arcs, so none would detect a loose connection.

GFCIs trip on a difference in current between the hot and neutral, not line voltage changes. They are primarily for electrocution protection.
The "slow short" you describe, an arc that trips a breaker slowly, if at all, is exacty what AFCIs are designed to protect against. A more likely cause is probably an abused extension cord.
AFCIs also include 30mA ground fault protection (GFCIs have 5mA protection). The idea is, I think, that if a ground wire is adjacent, a hot-to-neutral arc is likely to also become hot-to-ground.
bud--

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 26, 2006, 4:20 pm
Bud-- wrote:

Methos It sounds like bud has the right answer. I hadn't heard about the upcoming AFIC's but will certainly pass the info on to everyone at my office (I'm a construction administrator for a large architectural firm). Thanks bud for the education. LightsAREon

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 28, 2006, 9:20 pm
I don't believe it's "upcoming". I think that all AFCI's currently have 30ma ground fault protection for equipment.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 28, 2006, 11:53 pm
What is "30ma ground fault protection"? It takes less then 30 mA to kill a man.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 29, 2006, 3:05 am
On Mon, 28 Aug 2006 16:53:37 -0700, "Ook" <Ook Don't send me any freakin' spam at zootal dot com delete the Don't send me any freakin' spam> wrote:

They call it Ground-Fault Protection of Equipment when it is at the 30ma level. BTW get used to AFCIs. They will be on all 120v 15 and 20a circuits in a dwelling in 2008 if the code goes as drafted. Comments are still open until October.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 29, 2006, 1:58 pm
snipped-for-privacy@aol.com wrote:

Yea - it is to detect the arc, not protect people. AFCIs can have a 5 mA ground fault trip and be used as both AFCI and GFCI. It would require 2 test buttons. Probably would see them if the code change below goes into effect.
To PPS - I presume "upcoming" is the requirement to detect "series" arcs starting 2008, not 30mA ground fault trip.

Considering the new AFCIs aren't on the market (or are they recently out?), and it is only about 1.5 years for field experience until they are required in 2008, it seems like requiring the new AFCIs in all 15/20A dwelling circuits is not a great idea (whatever the wisdom of requiring the current AFCIs is). Bet there are plenty of comments on that code change.
An interesting piece on AFCIs, including why normal breakers are inadequate for arcs and arcs that shouldn't trip them is at: http://www.cpsc.gov/volstd/afci/AFCIFireTechnology.pdf
bud--

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 29, 2006, 6:20 pm
On Mon, 28 Aug 2006 23:05:55 -0400, snipped-for-privacy@aol.com wrote:

Wouldn't that be all circuits in new construction?
--
Mark Lloyd
http://notstupid.laughingsquid.com

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 30, 2006, 12:28 am
On Tue, 29 Aug 2006 13:20:08 -0500, Mark Lloyd

Usually it would be all the 120v ones.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 30, 2006, 3:43 am
On Tue, 29 Aug 2006 20:28:08 -0400, snipped-for-privacy@aol.com wrote:

There's no 240v AFCIs?
--
Mark Lloyd
http://notstupid.laughingsquid.com

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 30, 2006, 5:08 am
On Tue, 29 Aug 2006 22:43:28 -0500, Mark Lloyd

I believe there may be 240v AFCIs but they are not mandated in the code yet.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on August 30, 2006, 11:21 pm
Only requirement I'm aware of where GFPE's (30 ma GFCI) are required in the 2005 NEC is Section 426.28.
"Ook" <Ook Don't send me any freakin' spam at zootal dot com delete the Don't send me any freakin' spam> wrote in message

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on September 24, 2006, 12:33 am

What is an AFIC?
Thanks!
David

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on September 24, 2006, 3:54 am
On Sun, 24 Sep 2006 00:33:42 +0000 (UTC), snipped-for-privacy@panix.com (David Combs) wrote:
[snip]

An Arc Fault Interrupted Circuit. A circuit that has no current in it because you didn't use an AFCI, your house was on fire, and the fire department cut off the power.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• posted on September 26, 2006, 7:07 am
David Combs wrote:

Arc Fault Circuit Interrupter. The AFCI breakers look like, and wire like GFCIs. AFCIs trip on arcs. The NEC requires them on new circuits to bedrooms. The proposed 2008 NEC requires them for all residential 15 and 20A circuits IIRC (could still be changed though).
A good paper from the Consumer Product Safety Commission on AFCIs is at http://www.cpsc.gov/volstd/afci/AFCIFireTechnology.pdf It explains the rationalle for using AFCIs describes how they work.
bud--

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
• Share To

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.