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    Wunu's Avatar
    Wunu Posts: 5, Reputation: 1
    New Member
    		  
    #1

    May 2, 2012, 07:27 AM
    How do I know how much power comes into my building?
    I want to install a sub panel so that I can add some outlets and a clothes dryer into my workshop building. However, I do not know how to tell how much power is supplied from the utility pole into the building. I don't want to overload the system. I will also be adding a hot water heater but the original panel has the space for that. I currently have a 100amp panel and want to add another 100 amp panel in the hopes that as my workshop and abilities grow, I will be ready for that growth electrically speaking.
    I have a licensed electrician who is willing to check my work as I go, but I am hesitant to get the power company involved if I don't have to.
    Thanks in advance for the advice.
    Diana
    tkrussell's Avatar
    tkrussell Posts: 9,659, Reputation: 725
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    #2

    May 2, 2012, 07:35 AM
    You cannot tell what the power utility has available. Even your electrician will not be able to know.

    The utility sizes their system is based on derated values of the load submitted when the service was first connected.

    When new load is added, the utility is to be consulted so they can determine if they need to upgrade something on their end.

    You also need to be concerned with adding more load to your 100 amp service.
    Wunu's Avatar
    Wunu Posts: 5, Reputation: 1
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    #3

    May 2, 2012, 07:51 AM
    Curses! Thank you. I just realized too that I probably can't run a 100amp sub from a 100amp panel. That's 200 if everything is running and the first panel will likely trip. Is that correct?
    tkrussell's Avatar
    tkrussell Posts: 9,659, Reputation: 725
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    #4

    May 2, 2012, 08:34 AM
    Correct. Have your electrician size up your new panel and if the existing panel needs to be upgraded.

    If the service is upgraded, and/or if you are adding load, you need to consult with your utility.
    stanfortyman's Avatar
    stanfortyman Posts: 5,598, Reputation: 279
    Electrical & Lighting Expert
    		  
    #5

    May 2, 2012, 01:12 PM
    Quote Originally Posted by Wunu View Post
    Curses! Thank you. I just realized too that I probably can't run a 100amp sub from a 100amp panel. That's 200 if everything is running and the first panel will likely trip. Is that correct?
    Actually, no.

    It is still a 100A service, just with a 100A sub-panel. You do not add up the breakers.
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