100amp subpanel

Old 09-19-03, 05:45 PM
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100amp subpanel

I want to add a new 100amp subpanel approximately 75 from my 200amp main panel. I need to determine what size wire to use to feed this new panel. I have been told to use 3 #3's and 1 #8 for the ground. but when I went to buy this wire at the home center, the #3 the clear showed me was huge, around 1/2 inch in diameter. I need to know exactly what type (tthn,awg or something like that) so I don't get confused again. The subpanel will feed a 50amp to a hot tub and the rest is for future expansion. I have been told to run 3 #8's and 1#10.
Old 09-19-03, 06:14 PM
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#3 THHN or THWN wire is 0.352" in diameter.

Depending on factors not in evidence, you may either need #3 copper or #2 copper (which in THHN or THWN is 0.384" in diameter). Until we're sure, you might want to assume you need #2 copper.

#8 copper is good enough for the equipment grounding conductor.

Is the subpanel in the same building or differnent building? Are the terminations on the breakers and on the subpanel marked for 75 degrees, or only for 60 degrees? Will any part of this wire be outdoors or underground?

When you start wiring 100-amp panels, you're in the big leagues. The wire isn't going to be small.

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