Aluminum wire and plastic conduit or copper and metal?

Discussion in 'Electrical Forum discussion & Blog' started by leejosepho, Oct 22, 2008.

  1. leejosepho

    leejosepho DIY scratch-pad engineer

    I have purchased a new subpanel for my attached workshop, and now I need to decide about 100-amp wire and conduit. I can either run three strands of #3 copper in metal conduit for the ground or I can run a 2-2-2-4 aluminum twist in larger plastic. The subpanel will be 50' from my main panel, and I will have four 90* turns along the way. The copper wire would cost me a little over $150.00, and the aluminum would cost about $50.00 less ... but then the plastic conduit for the aluminum would have to be larger than the metal for the copper ...

    Also, I presently have a new and fine-for-now 60-amp breaker that might accept the #3 copper going to the subpanel, but I would have to buy a 100-amp breaker if I use the #2 aluminum wire.

    Which way should I go?
  2. jar546

    jar546 In the Trades

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    Location:
    USA
    Pull an electrical permit with hour municipality, then hire an electrician.
  3. leejosepho

    leejosepho DIY scratch-pad engineer

    ... and just who would be paying?!

    I decided to use 1" EMT and #4 copper, and changing the path a bit now means I will only have three 90s instead of four.
  4. leejosepho

    leejosepho DIY scratch-pad engineer

    Whew! Thank you.
  5. jar546

    jar546 In the Trades

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    Location:
    USA
    How do you plan on running the EMT, underground, overhead, along a wall? This is important because there are many ways that you cannot run EMT.

    What type of wire are you pulling and how many conductors? RHW, THHN, THWN, SEU, etc.

    What is the conductor fill capacity for 1" EMT and type of wire you are pulling?


    What code cycle is your municipality in?

    After you answer all of these questions you may get a little farther into understanding exactly what you need to do and why what you have planned so far will not work.
  6. leejosepho

    leejosepho DIY scratch-pad engineer

    I can guarantee you that what I have planned will definitely work, but I am nevertheless interested in hearing why you say it will not.
  7. Alectrician

    Alectrician DIY Senior Member

    Messages:
    689
    #4's will not do a full 100 amps.

    If you try to stuff #2's in 1" conduit, you will regret it.

    No one around here has #3 wire.


    Above ground = EMT

    Underground = PVC
  8. jar546

    jar546 In the Trades

    Messages:
    432
    Location:
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    Listen to 220/221

    Again, what code cycle are you on?

    This had direct bearing on grounding requirements.

    You will pulling 4 conductors I can only assume or at least hope so. This means that you can only fill 40% of the conduit cross sectional area.

    If you plan on 1" EMT which is wrong because it should be PVC then at the most you can get will be not enough so don't plan on using 1". Reason #1, it is too small for the size wires and if you still plan on doing it, I will fly down to video your attempt. It simply won't work and you will make America's Funniest Videos. Especially with 360 degrees of bends between pull points.

    If you are going to run 4awg XHHW aluminum then you will need to pull it through at least 1-1/4" conduit and that will be tough. Don't even think about pulling SE cable through because it will not work and it is a code violation.

    I am trying to help to save you a headache.
  9. leejosepho

    leejosepho DIY scratch-pad engineer

    Understood. I was hoping for 100, but I had to settle for the wire I could afford. So, and unless the #4 wire will not clamp into it, I will be using the 60-amp breaker I had already purchased for this project quite some time ago.

    Yes, I know. I used PVC to go out to a subpanel in my detached garage where we used to live, and now I will be using EMT to run inside along the wall to my attached workshop.

    I have no idea.

    It is my understanding that I only need three conductors since the EMT is a mechanical ground. But, I do have enough wire for four if necessary and I believe four will fit into 1".
    Last edited: Oct 31, 2008
  10. jar546

    jar546 In the Trades

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    Location:
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    EMT is not a mechanical ground if it is not continuous and since you are feeding a separate structure you will need an equipment ground. Again, without knowing what code cycle you are in there are other issues.

    You will have to use PVC so eliminate the EMT thought as far as a ground.

    It sounds like you are going to do whatever you want anyway because you already purchased the material so what is the point of asking?

    You may get it to "work" but that does not mean it is right or safe.

    These rules are written in blood because of incidences that have happened over the years causing loss of life, health or property. They are MINIMUM standards.

    Will you be taking the 2/2/2/4 back because yo can't run it through conduit or using it anyway? Sounds like SE cable to me.
  11. hj

    hj Moderator & Master Plumber Staff Member

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    wiring

    If you are resigned to using the 60 amp breakers, why would you stay with the 100 amp wires, given the additional cost for the larger conductors?
  12. mattbee24

    mattbee24 In the Trades

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    Location:
    Fremont, OH
    From what I understand, the sub panel is in an attatched building, and he is running emt along the wall all the way to the sub panel. He is using #4 copper to feed the sub panel. Around here, #4 copper is acceptable for 100a service in a residential home, and #3 for commercial. (he is using a 60a breaker so that point is mute anyway)

    As far as using the conduit as the ground, I didn't think you could do that, but I could be wrong.

    If he does need to pull a ground, it looks like he should still be able to do that. The chart I have shows you can have up to 4 strands of #4 thhn in 1" emt.

    That's just my opinion, I could be wrong.
  13. jar546

    jar546 In the Trades

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    Location:
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    He said he already purchased aluminum and your chart is wrong. THHN takes up more space than XHHW. There are two charts and a calculation that you must use in order to decide what can fit in conduit.
  14. jar546

    jar546 In the Trades

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    Location:
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    The problem in this situation is that the materials that were already purchased will not work.

    This is where the limitations of a DIY come into play.

    Something of this magnitude should be done professionally.

    Of course we can all keep asking the same questions to enough people so we eventually get the answer that we wanted to hear in the first place.

    IMHO
  15. leejosepho

    leejosepho DIY scratch-pad engineer

    Something has become all confused here. The EMT will be continuous, the subpanel will be in attached workshop and I have purchased copper wire.
  16. leejosepho

    leejosepho DIY scratch-pad engineer

    Partly because I got the wire at a good price, but also because I would rather run heavier wire than is actually required anyway.
  17. leejosepho

    leejosepho DIY scratch-pad engineer

    You definitely have the details of my structure and purchased-so-far supplies correct, and I am not yet absolutely certain about the EMT as the ground ... and if four strands of #4 actually do turn out to be too much for the 1" EMT, I believe I can use a smaller ground wire. The aluminum wire I had merely *thought* about using has a #4 ground running alongside three strands of #2. So, I can imagine #6 copper would be fine as a ground alongside #4 copper lines and a neutral if I must have a fourth wire even with continuous EMT.
  18. Furd

    Furd Engineer

    Messages:
    446
    Location:
    Wet side of Washington State
    The electrical codes are not items of uncertainty, belief or imagination. They are hard and fast rules and where enacted into law they MUST be followed. There is no place for uncertainty, belief or imagination. Follow the codes or do not do the job.
  19. Alectrician

    Alectrician DIY Senior Member

    Messages:
    689
    Even if you are not yet required to pull a ground, pull a #8 anyway.

    Grounding = good.

    The charts may say you can fit the wires in but the charts are often unrealistic. Does it still say something like 10 #12's in 1/2 EMT??? :eek:

    I recently re pulled 3, 4's + ground into an existing 1" EMT and it was NOT easy. An inexperienced person couldn't have done it without damaging the wire. Wires cannot twist or kink at ALL or they take up too much space.

    Run 1.25 or 1.5.


    But there are MANY places for interpretation.
    Last edited by a moderator: Oct 31, 2008
  20. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,561
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    North Carolina
    Anyone want to bet that this is what he is installing?

    click here
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