Here’s where I am at. I have a metal shop building about 160 feet from my main panel. I have a 400 amp service. I ran 2 inch pvc conduit about 36” deep. My wire is 3 wire 2awg use 2 aluminum with a 6ga insulated copper ground wire to the shop. At the panel I also ran an 8 foot ground rod with a bare copper wire to the subpanel ground. I am set up with a 60 amp breaker on the house panel. The shop has a couple 20 and 15 amp breakers and will likely run a 40amp breaker for a welder or plasma cutter. I don’t want to tear it all up again if I did something wrong but I’m not opposed to sizing the load down if I have to.

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    You need a disconnect at the shop building - either a separate disconnect switch or a main breaker. 60A in house protects the wire, so if you use a main breaker in the subpanel it can be any size 60A or larger. Also need either breaker/GFCI or receptacle/GFCI for all the 20A and 15A circuits. Oct 4, 2022 at 17:09
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    The USE-2 is 3 real separately insulated wires, NOT 2 real wires and an over-braid 3rd conductor?
    – Ecnerwal
    Oct 4, 2022 at 17:09
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    I should have added that the sub panel is a 100 amp square d with 100 amp main breaker. Do I need to install a gfci still? Do all my outlets need a gfci breaker? Thanks
    – Mark Wie
    Oct 4, 2022 at 17:37
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    You need GFCI protection. You don't need a GFCI breaker, other than for a 240V receptacle. The GFCI can be the first thing in line on the circuit. and will protect the rest of the outlets if wired correctly. Please verify the type of USE-2, since it comes in different styles, and which style matters, here.
    – Ecnerwal
    Oct 4, 2022 at 17:59
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    @MarkWie I'm trying to establish if you installed the cable style that is 2+ ground, (which can't be a neutral) or if the cable has an acceptable neutral conductor. USE-2 cables are made both ways. You described it as 3 wire and now you've described it as 6 strand. Edit in a picture of the end of the cable and that will clear things up.
    – Ecnerwal
    Oct 4, 2022 at 22:39

1 Answer 1


You did just about right, actually.

Ground rods, fat conduit, #2 aluminum which is approved for 90A in this circumstance (as feeder panel-panel).

There's no worries on voltage drop. You are only allowed to plan to load the #2 feeder to 80% of ampacity, so 72A. Given 160' and 240V power, your voltage drop would be 2.82% which is more than adequate. ("3%" is mostly a wire salesman's lie).

The only real risk here is getting too small a subpanel, thus painting yourself into a corner later and having to do a costly re-do. Breaker spaces are cheap and 90A wire can power a lot of stuff.

The subpanel does not need a main breaker. It needs a main disconnect near the point where the power enters the building, but - if the subpanel is there, a disconnect can be part of it. That is why you see people use main-breaker subpanels, they are using the main as a disconnect switch (for which it is more than qualified).

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