GFCI Question: Can Line And Load Wires Be Run Inside The Same Conduit? - Electrical - DIY Chatroom Home Improvement Forum


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Old 04-15-2009, 06:43 AM   #1
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GFCI question: can line and load wires be run inside the same conduit?


Let me explain: I'm trying to add GFCI protection to the basement outlets in my father's house, which was built in 1961. Most of the wiring is original, and is in pretty good shape. Although there is no ground wire, the entire house is snaked with 1/2 inch flexible metallic conduit, which serves as the ground conductor throughout.

The basement circuit I'm trying to protect serves lighting and outlets in a completely finished portion of the basement. The outlet closest to the breaker panel is served by a 14 ga. black and white pair ran through 1/2 inch flexible conduit which drops from a ceiling box in a utility room, down to the outlet. Nothing else continues off of that outlet.

The rest of the outlets and lights are served via other branches exiting the same ceiling box.

I'd like to add another black and white pair to that first outlet branch so that I can protect that outlet and the rest of the circuit through a single GFCI receptacle. (Actually, I'll just pull 4 new wires, using the two old ones to pull the four new ones through the flexible conduit--that way, I don't need to worry about damaging the 48 year-old insulation pulling new conductors right next to the old.) Since it's in an unfinished area, I'm planning to use a box extender on the ceiling box so that I can fit 10 conductors in there instead of the 8 that are in there now, and have it stay up to code.

Does this plan sound good? Is it OK to use white for both the load side and line side neutrals (I was going to use black and red for the load and line side hots), or do I need to use a different color, or reidentify it somehow?

Or is it out of the question? (In which case, because of how I reckon the circuit is laid out, I'd have to use 5 GFCIs instead of just one to protect 9 outlets, because busting open walls in this house is not going to happen.)

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Old 04-15-2009, 07:53 AM   #2
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GFCI question: can line and load wires be run inside the same conduit?


Yes you can use white for all neutrals, line and load sides of GFCI's included. I think light gray is a permissible color for neutrals but for the home DIY'er it's just an added expense for a supply of that color wire.

You may use black for both line hot and load hot. It is also permissible to mark black wires with red, blue, etc. (any color except white or green) tape at both ends for identification purposes if you wish.

Yes you may run the line neutral (and hot) out the single conduit from a junction box to the GFCI receptacle and the load neutral (and hot) back in the same conduit to the junction box (and off in a different direction from there) if that is the way the conduits were strung.

Double check to be sure this is 1/2 inch flexible conduit with individually strung wires as opposed to pre-made metal sheathed cables. The latter may have a paper lining inside the "conduit" occupying too much of the cross sectional area to allow 4 new wires.

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Old 04-15-2009, 09:38 AM   #3
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GFCI question: can line and load wires be run inside the same conduit?


Also, while it may be adequately grounded by the metal flex, it is technically not a code compliant grounding method. Metal flex over 6 feet long is not an approved grounding means, not even in the 60's. This is not to say that it won't work, however. If I were working on this, every box that I disturbed, I would tighten the conduit connection, just to be on the safe side.
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Old 04-15-2009, 12:09 PM   #4
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GFCI question: can line and load wires be run inside the same conduit?


If you have a bonding strip (thin aluminum or copper wire) the jacket can serve as the ground. Tighten the box clamp, in the 60s they left them loose sometimes.
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Old 04-15-2009, 12:25 PM   #5
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GFCI question: can line and load wires be run inside the same conduit?


He has FMC and is pulling in new conductors.
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Old 04-15-2009, 12:30 PM   #6
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GFCI question: can line and load wires be run inside the same conduit?


I should have said if he had bx. He said the house was built in 1961, same time bx was used.
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Old 04-15-2009, 12:36 PM   #7
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GFCI question: can line and load wires be run inside the same conduit?


He said

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Originally Posted by thegonagle View Post
........I'll just pull 4 new wires, using the two old ones to pull the four new ones through the flexible conduit.......
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Old 04-15-2009, 03:35 PM   #8
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GFCI question: can line and load wires be run inside the same conduit?


Yup, he should know that it might not be fmc though.
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Old 04-15-2009, 04:14 PM   #9
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GFCI question: can line and load wires be run inside the same conduit?


He didn't say FMC?
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.........the entire house is snaked with 1/2 inch flexible metallic conduit.......
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Old 04-15-2009, 05:42 PM   #10
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GFCI question: can line and load wires be run inside the same conduit?


Maybe I've been living a parochial existance, but I have never seen 1/2" flexible tubing!
BX cable cable, yes!
If its important to have GFCI on the circuit, why not install a GFCI breaker in the panel and be done with it. If the breaker is too expensive, a GFCI receptical could be installed at the electrical panel and the circuit fed down-stream from this!
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Old 04-15-2009, 06:35 PM   #11
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GFCI question: can line and load wires be run inside the same conduit?


Here is what FMC looks like:

http://www.amazon.com/dp/B000HEKU9A/...A&linkCode=asn

FMC was required in CA and still may be reguired in other areas like EMT is required in Chicago. It is still at all the supply houses here and is still popular because it makes electrical modifications easier. It comes in aluminum or steel with a whole range of fitting to connect to EMT or rigid.

1/2" FMC is rated for nine 12AWG conductors so adding capacity to an existing run can frequently be done without tearing open the walls.
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Old 04-15-2009, 07:02 PM   #12
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GFCI question: can line and load wires be run inside the same conduit?


Quote:
Originally Posted by Wildie View Post
Maybe I've been living a parochial existance, but I have never seen 1/2" flexible tubing!
BX cable cable, yes!
If its important to have GFCI on the circuit, why not install a GFCI breaker in the panel and be done with it. If the breaker is too expensive, a GFCI receptical could be installed at the electrical panel and the circuit fed down-stream from this!

Dang guy, you ought to see 4" fmc.

thegonagle: you need to check to see how many additional recpetacles you can feed from the GFCI device you have. It seems most I have used limit it to 4 or 5. Your post inferred you were intending on putting 9 receps on the one GFCI.


You should also check state or local code as to the need for an EGC. NEC does not require one in the manner of use you have but Michigan does. I don't know what Minn requires. Never hurts to have one though.
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Old 04-15-2009, 09:14 PM   #13
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GFCI question: can line and load wires be run inside the same conduit?


Nap is right on the egc (Equipment Grounding Conductor) When I moved into my 1954 house in 84 I found a 2400 sq ft FMC wired house that was fed by a six breaker panel with NO main. On the first box that I opened I found a two prong double D receptacle connected with a green and a white 14awg TW wire. When the house was built in 1954, green was an acceptable color for a conductor. I'm sure that there are still some houses here that have the same set-up.

It took almost a year to get everything replaced, moved the meter, up'd the service to 200 Amp (& moved it away from the meter) added two 70 amp SquareD load centers with a total of 54 breakers. I tore out every piece of the 60
C TW and pulled in almost every possible color of 90 C all 12AWG THHN. Every run had a green 12AWG EGC. I really did an overkill by making most of the breakers Square D GFCI's. Thank God this was before AF or I would have gone down that road.

I had to add some runs and also used some EMT and a little NMB. I had to because I was maxed out, on a few runs, on the conduit fill at 13, 12AWG wires (that was legal in the mid 80's) The whole thing was still overkill in a California house with all gas appliances and No AC, but it was fun. On the day of the inspection the inspector found one problem, an open box that had the last little unconnected unused piece of the old green TW. He solemnly told me "Remember, Green is Ground".
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Old 04-15-2009, 09:45 PM   #14
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GFCI question: can line and load wires be run inside the same conduit?


One thing you should be aware of is that according to Table 310.15(B)(2)(a) of the NEC, the ampacity of the wire must be derated if there are four current carrying conductors. The permitted ampacity for this line is now 80% of the rated 15 amps, i.e. 13 amps is now the max permitted draw through this line.
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Old 04-15-2009, 09:50 PM   #15
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GFCI question: can line and load wires be run inside the same conduit?


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Originally Posted by Bigplanz View Post
One thing you should be aware of is that according to Table 310.15(B)(2)(a) of the NEC, the ampacity of the wire must be derated if there are four current carrying conductors. The permitted ampacity for this line is now 80% of the rated 15 amps, i.e. 13 amps is now the max permitted draw through this line.
Sorta! It should be derated 80% of the max ampacity of the wire, not the circuit.
If the wire is 14 thhn/thwn then the ampacity is 25 amps, so you can still put the wire on a 15 amp breaker.

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Last edited by jbfan; 04-15-2009 at 10:45 PM. Reason: corrected information
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