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.

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.

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.

#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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Originally Posted by stanfortyman

#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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What size ground would I need

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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Originally Posted by stanfortyman

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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Does my neutral need to be the same size as my current caring conductors

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Originally Posted by jordanmc1019

Does my neutral need to be the same size as my current caring conductors

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If not what size could it be

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.