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Thread: How many neutral conductors do I need?

  1. #16
    Electrical Contractor jbfan74's Avatar
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    Mike: I agree with Chris. I just completed an install of 30 amp 240 to a stand alone shed, with a 60 amp disco on the building and passed.
    Yes I am A Pirate-Jimmy Buffett

  2. #17
    Electrician Chris75's Avatar
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    Quote Originally Posted by jbfan74 View Post
    Mike: I agree with Chris. I just completed an install of 30 amp 240 to a stand alone shed, with a 60 amp disco on the building and passed.

    And you should, 225.39 is titled, Rating of Disconnect.
    not sure how people end up with thinking the wire size is related to that.

  3. #18
    Electrician Chris75's Avatar
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    Quote Originally Posted by Old Coot View Post
    Bringing electricity from main panel to sub-panel @ shed 20 feet away. I'm using #12 THHN conductors in 3/4" conduit with two conductors providing 240V to a dedicated air conditioner outlet and two conductors for two separate 120V, 20A outlet circuits for hand tools, etc. My question is do I need to run two separate neutral conductors for those 120V circuits or is one sufficient? Thanks in advance for your help.
    I'm still a little confused on the first sentence, and with what the rest of the post describes.

  4. #19

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    Apologies..my original description was lousy. The 20-foot feed to the shed is from a subpanel. Within that subpanel will be a two-pole 20A breaker for my 240V air conditioner circuit and two 20A single-pole breakers for the 120V circuits. So in the conduit to the shed will be (for example) two black #12 THHN's for the 240V outlet and two red #12 THHN's for the 120V outlets. There will also be a green #10 THHN for ground. Question was how many neutral (white) #12 THHN's need to be in that conduit.

  5. #20
    Moderator & Master Plumber hj's Avatar
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    Again, it depends on how you wire them. If they are to two different power legs you can get by with one, but realize that there is a downside to doing so. Safer is separate neutrals for each circuit, then you do not have to worry about burning things out if you lose the neutral, nor burning something down if you were to switch breakers and wind up with both on the same leg.

  6. #21

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    Code says only one circuit can be run to the shed. All the info is above.

  7. #22
    Electrical Contractor/Instructor jwelectric's Avatar
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    Okay I agree that it is the disconnect that 225.39 is addressing instead of the circuit itself but that donít change the fact that only one circuit is allowed by 225.30 or the disconnect outlined in 225.31 or the fact that the disconnect must be service rated per 225.36.
    This building will also be required to have its own electrode system as outlined in 250.32 as well.

    What you all are telling this poor guy is nothing short of wrong in the fact that he is to supply a sub panel with several different circuits or for that matter feeding the building with more than one circuit.

  8. #23
    Moderator & Master Plumber hj's Avatar
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    It sounds like he is going to do it anyway, so at least we can help him do it safely.

  9. #24

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    Thanks all for the information; it's been an experience hearing from each of you. And again, apologies for initial poor explanation of what I'm trying to do.

    Yes, I'm going to do it anyway but using two neutral conductors as suggested. If I sound stubborn, here's why:

    Apparently if I was simply running the new 240V outlet and the two 120V outlets from the subpanel within the same structure (either using NM behind drywall or conduit if exposed) I would be "legal" even if the distance was much greater than 20 feet. I'm also guessing that that "legality" probably would extend to a shed attached to the structure holding the subpanel. So why is it all of a sudden "illegal" (or hazardous) if all the wiring is in conduit (buried well below code requirements)simply because there's a bit of open space between the structures.

    I'll defer to anyone who says what I'm going to do is "illegal", but can someone get it into my thick head why it is either illegal or hazardous?

  10. #25
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    So could someone give me a step-by-step guide, with NEC citations, as to how to proceed if I want to have 1 20A 240V circuit, and 2 20A 120V circuits, with a maximum load of 24A total, in an unattached shed 50' from the house?

  11. #26
    Licensed Electrical Contractor Speedy Petey's Avatar
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    Quote Originally Posted by Mikey View Post
    So could someone give me a step-by-step guide, with NEC citations, as to how to proceed if I want to have 1 20A 240V circuit, and 2 20A 120V circuits, with a maximum load of 24A total, in an unattached shed 50' from the house?
    The ONLY way to do this legally is by installing a sub-panel, so answering your questions "as asked" would be non-compliant and dangerous.

  12. #27

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    can someone get it into my thick head why it is either illegal or hazardous?
    I don't think you will get an answer to this. I am always interested to hear input though. Another person's perspective can be enlightening. My guess is that the code was written for larger structures bacause it make sense to have a separate system for a sepatate building.

    It applies to a shed or garage because there are no exceptions written in re: size.

    If I were doing the work, it would be almost just as easy to put a sub at the shed and split off from there so I'd avoid the liability and comply with code.


    answering your questions "as asked" would be non-compliant and dangerous.
    Well....non compliant anyway.


    Just run a sub.


    3/4 PVC. 18" deep from your house panel to the shed sub. Strap it coming up the wall.

    Pull in three #8 THWN (two blacks and a white) and one #10 green. Colored tape is also not compliant....but that's a whole nother thread.

    Terminate the ground wire in a ground bus kit that will screw to your panel enclosure. Make sure the neutral bus is isolated from the enclosure. Terminate the other end on a 2 pole 50 amp breaker. The ground and neutral wil go on the same bus if the panel is the service. Look and see how the other circuits are terminated.

    Run your 120 and 240 circuits from the new sub.


    Or stick with plan A.
    Last edited by Alectrician; 08-17-2008 at 02:13 PM.

  13. #28
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Quote Originally Posted by Speedy Petey View Post
    The ONLY way to do this legally is by installing a sub-panel, so answering your questions "as asked" would be non-compliant and dangerous.
    No, step one in the answers is "You need to install a subpanel." Now, go on to step 2...

  14. #29
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Quote Originally Posted by Alectrician View Post
    Pull in three #8 THWN (two blacks and a white) and one #10 green. Colored tape is also not compliant....but that's a whole nother thread.

    Terminate the ground wire in a ground bus kit that will screw to your panel enclosure. Make sure the neutral bus is isolated from the enclosure. Terminate the other end on a 2 pole 50 amp breaker. The ground and neutral wil go on the same bus if the panel is the service. Look and see how the other circuits are terminated.

    Run your 120 and 240 circuits from the new sub.


    Or stick with plan A.
    Sounds good, but drawing from NEC cites above,

    Why not a 60A breaker?

    Why not a grounding electrode at the shed?

  15. #30

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    Why not a 60A breaker?

    That's all I have on my truck



    Why not a grounding electrode at the shed?
    Assuming no metalic piping to a "shed"..........right?

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