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Service Drop Cable

Discussion in 'Electrical Engineering' started by Kissi Asiedu, Sep 12, 2005.

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  1. Kissi Asiedu

    Kissi Asiedu Guest

    What size and type of cable would the electric company use as service drop
    for a house with a load of 200Amps.
    What book or web site is recommendable of this topic. I'll like to learn
    more about load calculations.


  2. Probably 2/3. At The Home Depot, where I work in the electrical dept.,
    that is what we recommend to people for that purpose. In fact, I sold
    some today. I always remember it, because I usually only sell that
    stuff about once per month, and the spool weighs like 500 pounds.

    As far as I know, a single wire #2 will only do 100 amps, but in a 2/3
    200 amp service drop, there are of course, two #2s, so you get 200 amps.

    Please, all the EEs and electricians out there, correct me if I'm wrong.
  3. Chris

    Chris Guest

    Once again I am reminded why I do not use HD for electrical. :)
  4. Since I do not know what "2/3" cable is, I need an explanation. But if
    he is saying that two 100A conductors (one for each "hot") are capable
    of carrying 200A, then of course he is wrong.

    What cable *is* required, anyway?

    BTW, even if I go to an electric-supply warehouse, will they necessarily
    know the answer? It's the licensed electrician who is supposed to know
    the Code and what to use, not the guy behind the counter anywhere.

  5. Bud

    Bud Guest

    I discoverd the ground screws and ground clips I bought there are not UL
    listed (Halex brand) - it is a NEC code violation to use them.

  6. Chris

    Chris Guest

    You are correct if you go to a supply-warehouse, they may or may not know
    the answer. In this case any warehouse worth a damn would know. If they
    did not know they would either look it up or recommend someone that would
    know (i.e. a licensed electrician). I am pretty sure any outfit worth a
    damn would not spit out such a ridiculous, life and house threatening,
    answer. Than again, anyone asking such a question, might be very-well
    talked into hiring an electrician.

    We are taking about 200amps!!!!! Not something to guess at!

    I know enough that I would not have to ask the question. I also know enough
    not to advise other people with answers that could burn the guys house down.
    That is what licensed-electricians are for, or for that matter people in the
    know. The local electric supply company I go to has one or two licensed
    electricians. Normally I just check my data / configuration with them. I
    would bet my life savings that they would not say "but in a 2/3 200 amp
    service drop, there are of course, two #2s, so you get 200 amps".

    HD always sells the fact that licensed professionals work there. This is
    pure BS, and the post above drives it home even more. Granted the poor HD
    guy is not a licensed electrician, and I think it safe to assume that there
    is not one in the HD that he works at. For if there was I am sure that he
    would of been well-educated at giving out "guesses".

    My last venture at HD electrical I was looking for a 3-phase disconnect. HD
    "professional" said they do not carry 3-phase disconnects anymore and
    recommended using a single-phase disconnect and "hard-wiring" one leg.
    Wonder if this is the same guy?
  7. If by the Code you mean the NEC, then you are wrong. Utilities don't follow
    the NEC when sizing service drops. 2/3 means #2 aluminum, 3 conductors.
    That would be the "norm" for short service drops for 200 amp services. If
    the service gets a little long, then 1/0 aluminum would be used.

    Keep in mind that you cannot compare the conductor ampacity ratings in the
    NEC with those used by utilities. Overhead service drops by utilities are
    governed by the NESC not the NEC.

    Charles Perry P.E.
  8. Chris

    Chris Guest

    Is that the same brand as the 29cent 15amp outlets?

    Could never figure out how they can sell something so cheap. Obviously they
    are cheap outlets, but who in the world can even make cheap ones that cheap?

    I can only assume that they are "loss leaders".
  9. SQLit

    SQLit Guest

    What the utility uses has absolutely NOTHING to do with the way an
    electrician can do the job.
    Where I live, if you can even get an overhead service, you would use 4/0
    copper per phase and 3/0 for the neutral. If you want to use AL then one
    size bigger.
    The utility would connect to those wires using ASCR cable. I am not going
    to list the size, cause it does not matter.
  10. Guest

    The service drop (the overhead conductor) might be #2 but as Mr Perry
    says, that is the utility string wire in free air under the NESC. As
    soon as you get to the service point where they splice to the service
    ENTRANCE cables at the service head the minimum size is 2/0 copper or
    4/0 alumiinum. An underground service lateral will use the larger wire
    since it is not "free air".
    That is for a dwelling only. If this is any other occupancy you would
    use 3/0 copper or 250Kcmil aluminum

  11. A 2/3 is 2-gauge, three wire. The red and black for hot, 2-gauge, and
    the white for the neutral, also 2-gauge, and of course a bare ground,
    4-gauge, all twisted up into one big black cable.

    You are correct, it is the licensed electrician who is supposed to know.
    That is precisely why HD employees are told NEVER to quote code to
    customers, even in the unlikely event that they actually know. Also, we
    do not have a code book to look things up.

    But nevertheless, Home Depot is a DO-IT-YOURSELF store. So, of course
    the very first thing a customer would ask me is what wire do I use for
    <whatever>? If you know the answer already, great. 99.99% of people do

    You try telling the customer that comes in from his minimum wage job
    picking fruit and doesn't even understand english, to hire a 100 dollar
    an hour electrician. See what happens. Go ahead.

    I tell them what I know, to the absolute best of my knowlege.
    I am not a licensed electrician, I am open with that, it is not a
    secret. I am a 10 dollar an hour, recent university graduate that
    cannot get a better job for lack of real-world "experience". My degree
    is in telecommunications. Not EE. For Home Depot, this is close enough
    to work in the electrical department.

    In the Home Depot, in the middle of a low-income area of a major city,
    where I work currently, and I have worked at 4 different ones in
    California, some rural and some urban, not a single one has a real
    electrician. Why would a real licensed electrician that could be making
    like 100 dollars an hour want to work retail and make at most 15 dollars
    an hour?

    Nonetheless, I do have pride in my job, and always give the customer an
    answer that is to the best of my knowlege. Perhaps that is one of the
    reasons I read this newsgroup, to further my knowlege to the best of my

    I am one of the few people in my entire store that even have a college
    degree. At least 90% of this store does not.

    It was not me that recommended to hard-wire one leg of a 3-phase. I
    don't deal with 3-phase anything. You're right, Home Depot does not
    sell anything 3-phase. I am told it is because 3-phase is not commonly
    found in the home. That is good enough for me.

    So what is the right answer to the original question anyhow?
    To restate what I said before... Please tell me the right answer! I
    want to know!
  12. ? Depends. The utility will run #2, not 2/0, for the overhead service. #2
    in open air can easily carry the load. The only reason the utility would
    use larger conductor would be to avoid a voltage drop problem for longer
    runs. The service entrance has to be much larger than #2 as per NEC.

    Charles Perry P.E.
  13. Chris

    Chris Guest

    Do not think anyone could come up with a better response than you did.

    I am in no way bashing your efforts when I mention that HD advertises having
    licensed professionals. They advertise it, not you. It is clear to most
    who know a little, that this is not true. As you mentioned no licensed
    electrician is going to work at that wage. Although there might be some
    retired electricians that are the exception. These are few and far between.
    Problem is there are probably a lot of fools who shop at HD and think that
    they are in fact talking to a licensed individual. Were would I be if I had
    listened to the guy who told me to hardwire one leg of the 3 phase?

    Seems like you are over qualified for the job, even with the parallel
    degree. I have done a service connect a couple of times. Does this qualify
    me to give out answers? No. This is not like running 14/2 for a light
    switch. It will also vary from region to region and from electric company
    and such. You can see this by the more qualified answers in this post as
    they vary somewhat.

    It can also be argued that I was wrong is saying we are dealing with
    200amps. It might be said that we are dealing with an almost unlimited
    number of amps. You or the house is not going to trip any breaker at the
    power plant. Again another reason this is not like wiring a light switch.

    Still not sure what you are referring to as "2/3" and your explanation above
    leaves me even more confused. If you are not sure what 2/0 is please look
    it up. There is a huge difference between 2/0 and the 2 gauge you are
    referring to. I think 2/0 at HD has a grey jacket and is on the spools on
    the floor.

    Read the answers that people more in the know have posted here. From that
    you can arrive as close as possible what the correct answer is. I would
    suggest though that you focus your knowledge after the breaker panel. I
    would assume that 98% of the business arrives from that anyways.

    As most who know better here would tend to agree this is not something to
    guess at. If the OP had asked what gauge wire I should run for my 16amp
    compressor, you would see a lot of people responding. These same people
    know better than to respond to something as serious as a service drop, and
    will leave it to the more qualified individuals. It does nobody any good to
    guess at it.

  14. Have you ever worked in the utility industry? If you had, you would know
    what 2/3 is. It is 3 -#2 aluminum conductors. Often with two conductors
    insulated for 600V and one bare conductor. It is VERY common as a service
    drop conductor for houses. Perhaps I should explain what a service drop is.
    In the utility world, that is the overhead conductor running from the
    secondary of the transformer to the weatherhead on your house. Not sure why
    you are busting his balls when he gave the correct answer. What is uncommon
    is for a customer to install their own service drop conductors. It is not
    unheard of. If you have a farm service, for example, the utility may
    install a meter on a pole and the customer runs service conductor to all of
    his buildings. There of some examples where a trailer service may work this
    way also.

    Service entrace cable is different. It is required by the NEC to be MUCH
    larger. It is the cable running from the weather head to the meter base and
    from the meter base to the breaker panel (or disconnect depending on the

    Charles Perry P.E.
  15. Chris

    Chris Guest

    Not busting on anyone really, if it comes across as such sorry. Reread what
    he said about selling it to people. You do not sell service drops to people
    at HD!

    I just reread his 2/3. At first I thought he mentioned two hots and a bare
    ground. I know see that he had it right.

    My gripe is the term "probably". The term probably and any mention of
    cabling under 12/2 should not be in the same sentence. Actually probably
    and any current flowing cable should not be in the same sentence.

    Not something to guess at, and is something to leave for a person in the
    know, or licensed.


  16. Incorrect. I am referring to a #3 X 3 conductors. For my purposes, 2/0
    does not come in a cable with others, but seperately.

  17. I do know what 2/0 is.

    At HD, it has a black coating. Maybe some of them have grey, but at all
    of mine, it has been black. It really doesn't matter.

    It seems to me that the coating on those is not sufficient insulation,
    especially since they are not in a cable with other wires.

    I would agree as well. Unfortunately, I have to know a little about
    everything, since if someone asks, I have to tell them something. In my
    line of work, "I don't know" simply doesn't work.

  18. Yes, that is exactly what I am referring to. Except that the conductors
    are all stranded copper, and not aluminum. We don't sell ANY aluminum wire.

    Thank you for the explanation of what a service drop is. That is
    exactly the kind of information that I crave. Real world stuff.

    Now, doesn't this require the utility company to climb the pole in order
    to connect the cable to the secondary of the transformer and the meter
    on the house?

    So, "service entrance" is different from "service drop"?

    Many of my customers live in trailers. At a home depot where I used to
    work, in a rural area, many of the customers lived on farms.
  19. I meant, #2 X 3 conductors, 2 hots and 1 neutral. Plus the bare ground
    of course.
  20. SQLit

    SQLit Guest

    I meant triplex wire.

    Sorry for the confusion.
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