I'm 90% sure there is a 100amp breaker running to my shed subpanel but it was a homeowner job so I want to verify everything is correct.

The subpanel has no main breaker though but I can see these three wires running to the shed from the main house. There are no markings besides the white stripe on one and they are 0.4" thick, what AWG would this be?

I'm assuming two hots and a neutral, no ground? Any guesses as to what this wire is and if it is in fact made for a 100 amp breaker?

Edit: I guess another question is, do I need a ground as there isn't one.

enter image description here

enter image description here

  • 2
    Can you take the dead front off of either panel at either end and look at the cable there? Of course, it's safest if you kill the power first so that you don't accidentally electrocute yourself while fiddling around inside the panel. If you can get into the sub panel, you should be able to move those wires enough to find the writing on them that will tell you all about what they are.
    – FreeMan
    Oct 18 '21 at 13:46
  • 2
    Not an electrician but my guess is it's not correct if there's no ground. If you want to make sure "everything" is correct then a picture of both panels should be posted. Oct 18 '21 at 13:59
  • 1
    Looks like a serious (lack of) ground problem. Metal conduit works (generally) in place of a ground wire. But this doesn't look like metal conduit. Oct 18 '21 at 14:21
  • 2
    Is the ground/neutral picture in the main panel or the subpanel? If that is in the subpanel, you have a big mess because ground and neutral should be separate bars (and neutral not bonded to ground/case). Plus I see a neutral wire chopped off instead of being unscrewed- ABSURD! Oct 18 '21 at 15:43
  • 1
    Fair enough, @manassehkatz-Moving2Codidact. I wasn't sure, that's why I asked.
    – FreeMan
    Oct 18 '21 at 16:07

Based on your panel pic, it looks like you've got 2 AWG AL wire (green box) of type XLPE. However, the writing is a bit worn, so it's hard to tell for sure.

Close up screen cap of wire

If I'm wrong, I'm sure one of the electricians will be by shortly to let me know. I believe that this is sufficient and appropriate for a 100A breaker, so you should be good to go there. Again, one of the electricians will contradict that statement if it's wrong.

Additionally, I notice that in the LB in the first picture, the stripe on the wire looks distinctly white, while in the panel in the second picture, it looks distinctly yellow. Are those the same wire?

Please pay heed to the comments on the original question about:

  • The lack of ground wire between your main and sub panels.
  • The mix of ground & neutral wires on the buss bar
    • If this is the sub panel, they must be separated
    • If this is the main panel, it's fine the way it is.
  • The neutral wire that was cut off, but left attached to the buss bar. This should be removed, just to keep it tidy and to remove a possible/arc short point.
  • 2
    I'm only "real" as a low voltage guy, but 2 AWG aluminum is not rated for 100A, since it's 100A in the 90C column, and terminals are generally only rated at 75C (so 90A). The stripe is usually a neutral-wire indicator, and may have aged (or photographed) to look different, but if there are two unstriped and a striped, that will be the same thing both ends.
    – Ecnerwal
    Oct 18 '21 at 17:23

As FreeMan notes, this is 2 AWG aluminum wire.

2 AWG is allowed 90A, per Table 310.15(B)(16).

enter image description here

There's a rumor running around that #2 is good to 100A. That is false, as is plainly evident by the table above. However, the place that falsehood comes from is NEC 310.15(B)(7) -- a whole service to a dwelling are granted an 83% favorable derate -- so a 100A service to a home only needs 83A wire, meaning 90A wire will suffice for that. But this doesn't apply to an outbuilding like yours.

Change the breaker to 90A and you're all set.

As far as the ground wire, yes, yes, 1000 times yes! Run a discrete ground wire and separate neutral-ground in the sub. It will greatly enhance safety, and prevent your grounds out there from becoming "hot" if the neutral wire gets loose. However, FYI, that was not a code requirement until NEC 2008, so it may be code legal.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.