# OT: Electrical Code Question 120 V Branch Circuits.

• posted on April 1, 2004, 6:50 pm
I have a long wall, about 100' along which I want to run 3 "staggered" or "alternating" 120V branch circuits. What I would like to do is run 3/4" conduit with a box every 4 feet or so. Then I'd like to have circuit "A" appear at the first box and every third box thereafter. Then Circuit "B" would first appear at the second box and every third box thereafter. And finally Circuit "CB" would first appear at the third box and every third box thereafter.
My question is whether code permits having all of the wires for three separate branch circuits running through the same run of conduit and passing through the boxes for the circuits they aren't connected in.
Thanks, Paul

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<%-name%>
• posted on April 1, 2004, 7:22 pm

I assume you meant circuit "C" there at the end. I think this is OK if you aren't over-filling the conduit. There are limits. You might even be able to run a single neutral for all 3 circuits if you allow for twice the amperage in that wire. I'd check with the local inspector on that. In theory you would have 2 circuits on one phase and 1 circuit on the other so you could get 2X amperage in a shared neutral in that situation.

I'm almost certain this is allowed within the bounds of conduit filling. Your local inspector is your friend on getting the fine points.
Bill Ranck Blacksburg, Va.

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<%-name%>
• posted on April 1, 2004, 7:34 pm
He could legally put 7 #12s in a 1/2" but that is pretty tight and hard to pull. Spend the extra pennies and use 3/4 like he said and you can go up to 13, or have a real easy pull with his 7.

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<%-name%>
• posted on April 1, 2004, 7:31 pm
No problem with the code in running separate 120v circuits in the same pipe. You will have 6 current carrying conductors and you only need one ground. You can use the <metal>conduit but a green wire is a whole lot better/safer. Be sure you get big boxes. You will need 24.75 cubic inches if you only have one receptacle, 26.75 for 2. (assuming #12) Get 4x4x2 1/8 boxes with raised rings and you will be fine. It is always better to use a big box. Easier to work in.
The other issue is derating but if you are using 90c wiring like THHN, it's hard to find anything else, you will be fine with 6 conductors. (derated @ .8) since #12 is good for 30a and #14 is good for 25a when you apply the derating factor. You are still limited to a breaker size of 15a for 14 and 20a for 12 so there is plenty of derating "wiggle" room. Be sure not to put more than 4) 90 degree bends between pull points in your conduit. Happy wiring!

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<%-name%>
• posted on April 1, 2004, 9:59 pm

pipe.
better/safer.
have
Additionally, you will need to 'bond' your ground wire at each box and also connect to each receptacle. Easiest way is to purchase or make separate jumpers of bare solid #14 wire and attach it to the rear of the box in the provided threaded hole using, if purchased, the green shouldered grounding screw. ( #10/32x1/4) Then cut, strip and twist the ground wires to the jumper leaving one wire extended long enough to secure to the receptacle/s, subsequently secure with a green wire nut. They have a hole in the end to allow the longer lead to protrude and still compress the twisted ones. Most areas require any outlets not dedicated in garages to be ground fault protected. GFIs can be daisy chained to protect additional standard receptacles on the same circuit.
--
Chipper Wood

useours, yours won't work

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<%-name%>
• posted on April 1, 2004, 10:41 pm
Good point on the Equipment Grounding and GFCIs. The newer "greenies" have the pigtail made up in the wirenut already with stranded wire and a spade terminal. They are real fast to wire. .

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<%-name%>
• posted on April 1, 2004, 11:28 pm

*YES* I've got 4 circuits through a common conduit, Double-gang boxes, holding two duplex outlets each. With each outlet in any given box being on separate circuits. Gives me 2 circuits at any location, and 4 circuits 'within reach' anywhere.
The required 6 wires for my config was a _hard_ pull through 1/2" conduit, for the run with 4 90-degree bends in it (in less than 10 ft').
Care is required dealing with the neutral wires. Code requires that the     neutral be 'un-breakable' for the entire run. Have to pigtail on the outlets at any intermediate point. can't wire to the 1st outlet and then from that outlet to the next, (rationale: failure at the 1st outlet, or botched repair, could result in 'unconnected' "neutral" at the downstream outlet(s) -- a *definitely* unsafe condition. Thus, you've gotta be able to connect/disconnect the upstream outlet w/o affecting the neutral to the downstream ones.)
You could 'get away` with 1/2" conduit, but using 3/4" *will* make life a lot easier, and allow room for 'something you haven't thought of' to be added later.
You might also look at a product called "Plugmold", from Wiremold Corp. Surface-mount "conduit" with outlets built in at regular (options of like 3", to 2', as I recall) intervals.

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<%-name%>
• posted on April 2, 2004, 12:19 am
You can do it with just 4 conductors if you use 3 phase; 3 hots and a single neutral.
(Okay, I realize he will not have 3 phase available to him, but would it work that way if he did?)

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<%-name%>
• posted on April 2, 2004, 12:34 am

This is wandering off topic but yes you can run 3 phase WYE single phase loads with one neutral. This is usually a douple sized neutral because harmonics can make the currents add instead of cancelling.
It does point out aan important thing "on topic". Be sure you identify each neutral in this pipe so you match up the load end with the feed end. With 3 there is an easy method, Use one white stranded and one white solid, the third can be grey. (after the 2002 code change). Just be sure to write a note on the back of your hand so you remember which is which.

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<%-name%>
• posted on April 2, 2004, 5:00 pm
I'm not an electrician, but I did exactly this. I have a neigbor who is a residential wireman help me. When this question came up, he deferred answering it and asked his electrician mentor, a master electrician. The answer was "yes."
I didn't do nearly as long a run as you, but in principle the same type of construction.
Best to consult a master electrician in your area to make sure you're complying with all NEC and local codes.
Joe

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<%-name%>
• posted on April 2, 2004, 6:17 pm
Run bigger conduit. The number of circuits doesn't matter, the number of WIRES does.
I assume you are running 12ga wire. If I remember right, a 3/4 conduit can run about 4 strands of 12ga. The conduit itself should be no more than 20% full of wire, in order to allow heat to dissipate through the conduit walls.
And don't run Romex, if that's what you were planning. Romex cable is not designed to be run in conduit---the cable sheathing is the conduit, and putting more than one together in a small pipe will provide way too much heat insulation, resulting in hot wires and noisy connections.
Passing through boxes isn't bad, as long as the box is rated for that many wires. Each terminal box has (should have) a stamp or sticker proclaiming how many "wires" it can handle, but the term "wire" is strictly defined by the electrical code.
Is there a specific reason you are using conduit? If this is an interior wall, why not simply run Romex through the studs? Conduit can be a pain in the butt and an unnecessary expense.
I suggest you buy a homeowner-style wiring book, the Sunset "Complete Wiring" book isn't too bad. It has a lot of really good basic information like this. Further suggestion is to use individual wires in 1-1/4 inch conduit, or two runs of 3/4. I would use 3 hot wires, 1 oversize neutral, and 1 ground wire. All wiring connections MUST be inside a terminal or junction box. (In other words, measure before you cut!)
Also, call your local permit office and ask to speak to an inspector. They all know the codes and I'm sure they would be glad to help.
PBS wrote:

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<%-name%>
• posted on April 2, 2004, 6:55 pm

Please, please don't listen to this guy, he knows not whereof he speaketh.
Please, please do consult the NEC fill tables for the correct information about fill percentages. (Hint, you can have many more than 4 strands of 12AWG THHN in a single 3/4" conduit). Note also that the ampacity of the conductors must be derated based upon the number of current carrying conductors in the conduit.

Noisy connections? WTF?

Again, consult the fill tables in the NEC. Boxes don't have stickers with fill ratings.

If this is the book used for the information in this post, throw it away, now. Better yet burn it so nobody else will use it.

Nuts. And a violation of code. The grounded conductor must be in the same raceway as the current carrying conductor. Which, if one is using either a so-called split-phase circuit, or an oversized grounded conductor for multiple current carrying conductors, implies that all conductors must be in the same raceway.

Well, one nugget of fact, after all.

Hey, there is one piece of good advice in this after all.
scott

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