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Thread: Subpanel

  1. #1

    Default Subpanel

    I would like to install a subpanel in the basement of my church for a new
    technology center they are building. Here's the existing electrical scheme:
    3-Phase 400A service from street (due to elevator). Main Panel to three
    subpanels: two 100A panels on each of the new addition floors and one 200A
    existing church panel. I would like to break off of the first floor panel (100A)
    into another subpanel in the basement. I'm assuming what I would have to do is
    run 3-8 cable between these two. What kind of breaker (amperage) is needed in the
    existing first floor panel to power the basement panel? Is it indeed 3-8 or is it
    4-8? Then would it be necessary to put a main breaker in the basement panel? Once
    my main is installed the branch circuits in the basement are easy. Nothing
    special just eight or so 15A breakers to power computers/network, lights, and a
    box air conditioner. Let me know if you need more information.
    Thanks for your help.

  2. #2
    Electrical Contractor/Instructor jwelectric's Avatar
    Join Date
    Jun 2007
    North Carolina


    Bless your heart Ben

    The size of the panel and the conductors ran to it would depend on the calculated load that is being installed.

    To ask about 3-8 cable in nothing more than a guess as to what the weather is like on the other side of the universe.

    A couple of things that I can answer are;

    Yes you would need to install both a grounded (neutral) and an equipment grounding conductor with the ungrounded (hot) conductors.
    You made the statement that the church has a three phase service and the number of ungrounded conductors would depend whether you are installing a single phase or three phase panel.

    No the panel will not be required to have a main disconnecting means but it is very advisable

  3. #3


    right!! oops.

    We i was thinking using a 40 amp breaker in the first floor panel. Our basement panel would be single phase. But would i need to run a total of 3 or 4 conductors between panels? And how do I find out if the 40A breaker I would install would trip the 100A main? And if 40A is enough/too much.

  4. #4
    Licensed Electrical Contractor Speedy Petey's Avatar
    Join Date
    Jun 2007
    NY State, USA


    Ben, I agree that this is a noble thing you are trying to do. It is very good of you to want to help. The biggest help you can do in this case is to NOT do this job. Seriously.

    First off, three phase is NO place for anyone inexperienced. From the sound of your questions you likely do not possess the experience knowledge to get this job done properly and safely.
    Second, a church is NO place for anyone inexperienced to be doing electrical work. Believe me, I KNOW this first hand. I do ALL the electrical work at my wife's school, which happens to be a parochial school, so I get roped into doing most of the work at the church as well.
    A church is a VERY critical place when it comes to electrical work. I have seen some unbelievable work done by folks trying to help. I am not saying this would be you, but you do not want that kind of responsibility hanging over your head.

    PLEASE have them consider having a licensed, insured contractor do this job. The peace of mind is well worth it!

  5. #5


    alright then- ballpark figure as to how much labor would cost to put in and wire a new panel.

    and yes my plan was to get the wire, run it, run branch circuits and then have a pro hook it up.

  6. #6
    Electrician frenchelectrican's Avatar
    Join Date
    Jun 2007
    NE Wis / Paris France { In France now }


    Ben ,,

    I hate to crash on ya but no hard feeling in here but i will echo speedypete's comment here.

    I do work on few church as well if they need me but really it will be much wiser just get the real electrician to come in and get this subfeed box hook up propely and the correct type of wire and materals because the main thing is the code i just can't list everything in here but i will make it short and blunt

    the code will really varies depending on type of building and how it will be used and number of pepole total in that buliding [ the code can change pretty fast depending what the building layout is ]

    the cost for electrician to come out and hook up that part i just want to be fair with ya i just cant tell you the cost because there is so many thing we have to cover all the details

    but get at least 3 electrician to sumbit the bid to cost to do the work if you want to do some of rough in you have to talk to the electrician whom will write the estame for this .

    Merci , Marc


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