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    wildcatmike's Avatar
    wildcatmike Posts: 11, Reputation: 3
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    #1

    Feb 13, 2012, 10:35 PM
    How to figure capacity to add a sub panel
    Hello all. I'm finishing part of my basement and making it a workshop. Because of all the new circuits I need, I'm quickly running out of space for new breakers. I'm thinking I need to add a sub panel (it would be right next the current one). I noticed that my main panel is only 150-Amps (I know, it's unusual... part number TM3215CCU). I attached a picture of what breakers are currently installed. These were all installed by the builder in 2003 when the house was built.

    I there an easy way, or rule of thumb I can use to determine how large of a sub-panel I could install? Right now, I'd like to add four circuits for the workshop (one 15-amp for lights, three 20-amp for tools) plus one additional 20-amp circuit to add to the existing finished area since the previous owner did a DIY job and only put one outlet in the entire finished basement :-( I also have future plans (dreams?) to add a hot tub, which will require its own sub panel outside (I did this once before on a previous house but there was plenty of capacity to spare in the main panel, so it was easy).

    Thanks in advance for any advice you have to share!
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    donf's Avatar
    donf Posts: 5,679, Reputation: 582
    Printers & Electronics Expert
    		  
    #2

    Feb 15, 2012, 09:23 AM
    Hey Mike, are you a "UK" Wildcat?

    Unfortunately, the panel circuit listing is not all that helpful. What you really need to do is a panel load calulation to verify if your panel has enough amperage to support the total service needed for your residence.

    Article 220 of the NEC starts this process for you.. If you do not know how to do this, then please contact a licensed electrician to do this for you. Also, since the Local Authority Having Jurisdiction will require a permit and a plan for the additional work, you might as well request the electrician to sketch the plan for you.
    wildcatmike's Avatar
    wildcatmike Posts: 11, Reputation: 3
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    #3

    Feb 15, 2012, 09:38 AM
    Thanks for the answer donf. I thought that would be the case but thought I'd ask first before shelling out the money to hire someone.

    ... and yes, I'm a UK wildcat... class of '99. Go cats!
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
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    #4

    Feb 15, 2012, 10:20 AM
    Mike,

    I was aat "Lexmark" from 1991 through 2005 when I retired.
    wildcatmike's Avatar
    wildcatmike Posts: 11, Reputation: 3
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    #5

    Feb 15, 2012, 10:38 AM
    It's a small world! My father-in-law has been there since the IBM days.
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
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    #6

    Feb 16, 2012, 08:18 AM
    Mike,

    I was transferred from IBM (24 years) in 1991. I was at Lexmark from 1991 through 2005.
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