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#200074 - 03/20/11 12:42 AM 3wire and GFI's  
MAH  Offline
New Member
Joined: Mar 2011
Posts: 7
Saskatoon, Saskatchewan, CA
First off I'm an apprentice, so go easy smile

I recently learned that my supply authority will not allow 2 separate GFI devices to be fed from a 3 wire circuit. For example a 14/3 supplying 2 GFCI devices in a single box with the neutrals tapped in the box before the GFCI devices, the resulting answer to supplying these would be to run 2 runs of 14/2 to supply the devices. I have searched the code book for a couple of days now and have come up empty, maybe its a combination of rules that lead to this interpretation but I fail to see the difference of the joint in the box and the neutral bar in the panel.

Tools for Electricians:

#200076 - 03/20/11 03:18 AM Re: 3wire and GFI's [Re: MAH]  
EV607797  Offline
Joined: Oct 2006
Posts: 745
Fredericksburg, VA, USA
Wow, that doesn't make any sense. The functionality of the GFI doesn't happen until it receives a feed. A shared neutral ahead of them shouldn't matter. I'm positive that the GFIs aren't going to know the difference.


"But the guy at Home Depot said it would work."

#200079 - 03/20/11 06:34 AM Re: 3wire and GFI's [Re: EV607797]  
sparky  Offline
Joined: Oct 2000
Posts: 5,319
Would this be in a location an AFCI is required?


#200085 - 03/20/11 03:53 PM Re: 3wire and GFI's [Re: MAH]  
MAH  Offline
New Member
Joined: Mar 2011
Posts: 7
Saskatoon, Saskatchewan, CA
I will explain the particular situation to clarify

I built a display panel for our company for a local home show, and the inside of the panel was open for display but I did not terminate the receptacles that were in 1110(handy) boxes because the panel was never to be energized and only for show. I ran a 2 wire to a standard receptacle that was fed from an AFCI breaker, and I ran a 3 wire to another handy box which was originally going to be a split receptacle and in my haste I mounted the GFCI receptacle to it(but not terminated). When the inspectors came around to inspect the booths they pointed out the 3 wire to a single 1110 box with a GFCI receptacle and we were told to change it even though it was a de-energized panel with no practical way to energize it easily. So me on the defensive asked why we cannot supply 2 GFCI devices from a 3-wire and the only answers I have gotten are 1 You are not supposed to, 2 Its against code. I have looked for a code but have come up with nothing saying one way or another, but I'm concerned that my understanding of GFCI's may be flawed when I fail to see the issue and the people I learn from and the authorities are telling me this is not an accepted trade practice

Oh and the issue of box fill in an Handy box was never brought up so its not a misunderstanding of the violation

Thank you for the replies

#200101 - 03/21/11 12:25 AM Re: 3wire and GFI's [Re: MAH]  
twh  Offline
Joined: Mar 2004
Posts: 922
Regina, Sask.
It's a perfectly correct installation. The trade practice is that the inspector must quote a rule.

#200102 - 03/21/11 01:14 AM Re: 3wire and GFI's [Re: MAH]  
MAH  Offline
New Member
Joined: Mar 2011
Posts: 7
Saskatoon, Saskatchewan, CA
I appreciate the input, when I was told this it was as if someone had told me the sky was yellow. I won't use this to argue with my journeyman or the supply authority, but at least I feel competent again with my understanding of how this wiring method works. I'll save that argument for when I'm a j-man haha

Thanks everybody, I'm enjoying this forum very much

#200104 - 03/21/11 07:11 AM Re: 3wire and GFI's [Re: MAH]  
sparky  Offline
Joined: Oct 2000
Posts: 5,319
1 You are not supposed to, 2 Its against code.

that takes a lot of us down memory lane MAH

the trade really isn't as obligatory in it's tutalage to the up and comming as it should be

used to get me down a lot when i wore your shoes

what i often countered with was politely asking 'how would you like to see it ?' , hopefully prying an explanation out


#200116 - 03/21/11 09:28 AM Re: 3wire and GFI's [Re: MAH]  
jdevlin  Offline
Joined: Aug 2002
Posts: 402
welland ontario canada
Unless it is a kitchen counter receptacle that is required to be split I think the inspector was wrong.

#200146 - 03/22/11 05:43 AM Unbalanced Current [Re: MAH]  
pooL8  Offline
Joined: Feb 2011
Posts: 56
BC Canada
I know from experience that it works just fine. I put in two outside gfcis this way at the house 2 doors down from me 3 years ago. But I also fed lights from the gfcis.
No problems yet.

How I see it is... if Gfcis compare the current at their hot terminal to the current at their neutral terminal, then what lies beyond isn't even readable. Proof of that is when you wire a plug off of from a Gfci's line. It doesn't protect that plug, cause it doesn't detect what's outside of it, unless you hook to loadside ofcourse.
Same principal as tapping a smaller wire to a BBH. The wire only sees what the heater puts out, not the entire circuit current

We have been told:
"The neutral carries the unbalanced current of a multiwire branch circuit" ...true
"Gfci's trip on a 4mA unbalanced current"...true

And that's where lots of people stop, I think... and a norm developed. Two different unbalanced currents thought of as the same?

Wouldn't this situation be the same as using a 2-pole Gfci breaker to feed two different branch circuits on a 3-wire?

#200160 - 03/22/11 06:24 PM Re: Unbalanced Current [Re: MAH]  
mikesh  Offline
Joined: Jun 2006
Posts: 613
Victoria, BC, Canada
As long as the GFCI outlets are after the split in circuits (out in the field) then the outlets will work correctly. You cannot use a 1 pole GFCI breaker and a normal 1 pole breaker on the other phase and have the GFCI breaker hold.

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