New 40x50 metal sub panel install

[Donniepowell]

First post but been lurkingfor a while. Well after several years I finally have my building going up tomorrow. I have the electric guys coming out but thought I would lean on you guys for some reassurance. I have read and searched numerous threads here and seems several opinions on wire to panel. I don't have access to mobile feeder wire and honestly don't want to wait on ordering it. It appears I am limited to copper and I am fine with that. Here is what I need to do

100a sub
Have space in panel for breaker
2 inch stub in concrete
Aprox 125 ft run to shop

2 options are
1- run from panel through attic to back side of house down the wall and trench to shop
2- run outside panel and bore under sidewalk and navigate septic to shop

Any suggestions of what would be more efficient.

Last question is wire size. Will thhn #4 for the 2 hots, #6 for the neutral and #8 for the ground work?

Great place here and have tons of ideas, just have to get the basics completed first. Electrical will start Friday.

 

[nwav8tor]

Not an expert, but I think you'd need at least three #2 for the hots and neutral and #4 for the ground, Might even need a bit larger due to the length of the run to account for line loss/voltage drop. This assumes you want to have the full 100A at the sub-panel.

As for your listed run path options, I'd vote for number one.

Hopefully some of the experts will chime in later...

Paul

 

[Donniepowell]

Thank you Paul, i am leaning toward that path. The other half is wanting it out of sight so it will take a little coaxing. I am curious to hear what the experts have to say for sure.

 

[Aceman]

Option #1 would require you to run conduit all through the attic or run a cable instead and splice to individual conductors before it goes underground. Requires a j-box, splices(I like insulated taps myself, but not necessarily cheap) and a few more parts.

For that reason, I would go lean towards option #2 myself. It's a cleaner install, no extra splices, j-boxes, or different wire types.

But, does your panel outside have capabilities to add a breaker for feeding the shop?

If running copper you need #3, you could probably drop down to a #4 neutral without issues if you have some 240v load out there. #8 ground.