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    jordanmc1019's Avatar
    jordanmc1019 Posts: 5, Reputation: 1
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    #1

    Mar 14, 2009, 09:37 AM
    Wire size for a 100 amp sub panel 200 feet away
    I have a 200 amp main panel in my house and I just built a garage and am planning on putting a 100 amp sub panel in the garage. The garage is about 200 feet from my house and it has a 2 inch pvc stubbed out underground. I am wondering what size aluminum I would need to feed it, and if I can use a smaller pvc.
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    jordanmc1019 Posts: 5, Reputation: 1
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    #2

    Mar 14, 2009, 11:05 AM
    I should add that the garage is detached and that I have a 50 amp 240 V welder and a 30 amp 240 V lift and there will be some convenience outlets and lights.
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    Tev Posts: 232, Reputation: 20
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    #3

    Mar 14, 2009, 11:14 AM

    You would need 2/0 aluminum. Your equipment grounding conductor can be 6 AWG aluminum or 8 AWG copper. 2 inch PVC is the correct size for the three 2/0 THWN wires and the grounding wire.
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    stanfortyman Posts: 5,598, Reputation: 279
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    #4

    Mar 14, 2009, 11:49 AM
    #2cu or 1/0al is all you need. Even that is considering a full time load of 80 amps, which you are likely never to see.
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    jordanmc1019 Posts: 5, Reputation: 1
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    #5

    Mar 24, 2009, 02:48 PM
    Quote Originally Posted by stanfortyman View Post
    #2cu or 1/0al is all you need. Even that is considering a full time load of 80 amps, which you are likely never to see.
    What size ground would I need
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    stanfortyman Posts: 5,598, Reputation: 279
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    #6

    Mar 24, 2009, 03:13 PM
    Normally a #8 ground would be correct, but since you are increasing the size of the feeder you must also increase the size of the ground.
    Without doing all the calculations I think a #6cu would be fine.
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    jordanmc1019 Posts: 5, Reputation: 1
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    #7

    Mar 31, 2009, 07:22 AM
    Quote Originally Posted by stanfortyman View Post
    Normally a #8 ground would be correct, but since you are increasing the size of the feeder you must also increase the size of the ground.
    Without doing all the calculations I think a #6cu would be fine.
    Does my neutral need to be the same size as my current caring conductors
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    #8

    Mar 31, 2009, 07:23 AM
    Quote Originally Posted by jordanmc1019 View Post
    Does my neutral need to be the same size as my current caring conductors
    If not what size could it be
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    KISS Posts: 12,510, Reputation: 839
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    #9

    Mar 31, 2009, 08:14 AM

    Having the neutal the same size as the current carying conductors basically means that the entire 200 A at 120 is being fed from one side of the panel.

    The neutral can be reduced by the 240 volt loads. e.g a 50 A 240 V load, can be take off 50 A at 120 V since the neutal will be 0 for this load. So, you could deduct 80A @ 120 V from the total. These loads are not continuous, so you can even deduct more.. 1.25 * 80.

    You would have to look at the other stuff too.

    If you went with the same neutral size, then you could have 100 A of 120 from one leg and 100 A from the other at 120V. With a lower neutral size, the you can't.

    The neutral carries the difference of the two hots.
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