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Thread: Aluminum wire and plastic conduit or copper and metal?

  1. #1
    DIY scratch-pad engineer leejosepho's Avatar
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    Default Aluminum wire and plastic conduit or copper and metal?

    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. #2

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    Which way should I go?
    Pull an electrical permit with hour municipality, then hire an electrician.
    http://www.inspectpa.com/forum/forum.php
    My answers are based mostly on the ICC codes. Advice given is my personal opinion and every person performing work should acquire a permit from his/her jurisdiction and get the work inspected. My opinions are not directions to follow for DIYs or professionals

  3. #3
    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by jar546 View Post
    ... hire an electrician.
    ... 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. #4
    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by jar546 View Post
    As long as you pull a permit and get it inspected as your project is being built then I don't care who does the work.
    Whew! Thank you.

  5. #5

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    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.
    http://www.inspectpa.com/forum/forum.php
    My answers are based mostly on the ICC codes. Advice given is my personal opinion and every person performing work should acquire a permit from his/her jurisdiction and get the work inspected. My opinions are not directions to follow for DIYs or professionals

  6. #6
    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by jar546 View Post
    ... what you have planned so far will not work.
    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. #7

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    #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. #8

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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.
    http://www.inspectpa.com/forum/forum.php
    My answers are based mostly on the ICC codes. Advice given is my personal opinion and every person performing work should acquire a permit from his/her jurisdiction and get the work inspected. My opinions are not directions to follow for DIYs or professionals

  9. #9
    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by 220/221 View Post
    #4's will not do a full 100 amps.
    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.

    Quote Originally Posted by 220/221 View Post
    Above ground = EMT

    Underground = PVC
    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.

    Quote Originally Posted by jar546 View Post
    Again, what code cycle are you on?

    This had direct bearing on grounding requirements.
    I have no idea.

    Quote Originally Posted by jar546 View Post
    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.
    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 by leejosepho; 10-31-2008 at 03:27 AM.

  10. #10

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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.
    http://www.inspectpa.com/forum/forum.php
    My answers are based mostly on the ICC codes. Advice given is my personal opinion and every person performing work should acquire a permit from his/her jurisdiction and get the work inspected. My opinions are not directions to follow for DIYs or professionals

  11. #11
    Moderator & Master Plumber hj's Avatar
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    Default 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. #12
    In the Trades mattbee24's Avatar
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    Default

    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. #13

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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.
    http://www.inspectpa.com/forum/forum.php
    My answers are based mostly on the ICC codes. Advice given is my personal opinion and every person performing work should acquire a permit from his/her jurisdiction and get the work inspected. My opinions are not directions to follow for DIYs or professionals

  14. #14

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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
    http://www.inspectpa.com/forum/forum.php
    My answers are based mostly on the ICC codes. Advice given is my personal opinion and every person performing work should acquire a permit from his/her jurisdiction and get the work inspected. My opinions are not directions to follow for DIYs or professionals

  15. #15
    DIY scratch-pad engineer leejosepho's Avatar
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    Default

    Quote Originally Posted by jar546 View Post
    EMT is not a mechanical ground if it is not continuous and since you are feeding a separate structure ...
    Something has become all confused here. The EMT will be continuous, the subpanel will be in attached workshop and I have purchased copper wire.

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