In my house I have a main panel with 3-50 amp breakers feeding a subpanel right next to it. The main panel has an opening for a double breaker.
I plan on adding a 50 amp 2 pole breaker to the main panel that will feed a second subpanel in a building that will have a 30, 20, and 15 amp breaker. It will be 240/120 service. I'm using #4 gauge aluminum service wire direct burial between house and building.
Is there a problem with any of this?
Best Answer
Use conduit
Putting in some 2" schedule 80 PVC now is a cheap investment compared to having to dig up a busted cable to replace it.
Torque your lugs to spec!
Get an inch-pound torque wrench and torque your breaker and panelboard lugs to manufacturer's spec. This is a new requirement with the 2017 NEC, spelled out in 110.14(D), and simply good practice anyway, especially with aluminum (which is a bit more sensitive to torques than copper is).
Make sure the outbuilding is grounded
Since you have a feeder to a subpanel at the outbuilding, you'll need to put in a ground electrode at the outbuilding and wire it to the ground bar in the subpanel, which will be separate from the neutral bar, by the way. (Make sure to pull that bonding screw or strap in the new subpanel!)