re: Electrician Help: Direct burial wire size from house panel to feed shed 60A sub panel

Ok, so using the following:
- 60A breaker at main panel
- 225' conductor length
- AL conductors
- Direct Buried

You now have to try and guess how much current will actually be drawn by equipment on the subpanel. Here are some limits based on a starting allowable conductor size of #6 AWG and allowing a 3% voltage drop from the main panel to the sub panel:
- #6 AWG & 11A load = 2.95% voltage drop
- #4 AWG & 18A load = 3.09% voltage drop
- #3 AWG & 22A load = 3.06% voltage drop
- #1 AWG & 33A load = 3% voltage drop
- #1/0 AWG & 38A load = 2.97% voltage drop
- #2/0 AWG & 50A load = 3.05% voltage drop

You probably wouldn't want load a 60A breaker more than 48A. If you get an idea of your largest equipment loads and you know you wont run them all at the same time, you can probably get by with smaller conductors. I dont know what kind of equipment you'll have but at the very least I'd probably go with #3 AWG if you only have 20A breakers in the sub-panel. If you end up with something like a 40A breaker in the sub-panel, i'd probably go with #1/0 to be safe.

The NEC recommends no more than a 5% voltage drop. By assuming 3% for this calculation, you have 2% voltage drop available from your sub panel to the end devices. There will be voltage drop in the branch circuit wiring and extension cords.