100 AMP Sub-Panel minimum wiring requirement

[Hamberg]

70' run from service panel. Am I reading the NEC correctly minimum #4 copper or #2 ALU?

 

[Sparky617]

Depends on the type of wire, but yes. Use service entrance cable.

 

[Hamberg]

Best choice, SEC 2-2-2-4? SEC Cable

 

[Sparky617]

Best choice, SEC 2-2-2-4? SEC Cable

In aluminum is I used for my basement sub panel. The 4 goes to the ground buss. You must also separate your ground buss from your neutral buss at the sub panel. They don't come together until the main panel. You'll likely need to buy a ground bar to accomplish this. For whatever reason they don't put a separate one in, though I bet on 95% of the panels they are a sub panel and not the main panel. Here is it pretty common to have a main panel under your meter, and then a sub panel in your garage and/or basement. My HVAC, sub panels, range, and EV circuit are all powered at the main. All the branch circuits are off one of the now two sub panels.

 

[Guzzle]

Don't know the NEC but for 70' aluminum at 3% voltage drop you can pass 200A, and at 100A you'd get less drop.
This #2 AL is very popular.

Pulling just 100A from my main panel would give me a 2% drop. We might have 200A service, I'm not sure..