I am finishing out a bath and laundry room in my basement and as part of the project I will need to add several circuits to the basement. Since my main 200 amp box is nearly full, and on the other side of the house, adding a sub-panel on the bath/laundry side of the basement seems like a good solution.

I know I can't put a subpanel in a bath, but can I put it in the laundry room as long as I meet the 36" clearance requirements? The wall on the side of the washer and dryer has about 5 feet of clear space in front of the washer and dryer, and there are no pipes or other obstructions in the wall. It seems like a good location for the sub-panel. Any comments?

I would also like to use a relatively large sub-panel because it would give me shorter runs if I need to add any future electrical circuits to the back yard or porch. A 100 amp Square D QO sub-panel (my main 200 amp panel is a QO) is bigger than I need now, but I don't see any major downside of oversizing. If I run cable for 100 amp service it will make the wiring a little more expensive, but will provide a lot of flexibility in the long run.

Is #3 copper THHN sufficient for 100 amps for about 50 feet of conduit in a dry area, or would there be a good reason to use larger? It looks like #4 copper might even be enough, since its rated at 95 amps, but I've seen conflicting information on whether its close enough to be allowed.

Thanks,

Bruce