The power panel in the garage has a 100 amp main breaker. There is a double pole 60 amp breaker that feeds a sub-panel in the barn. The sub-panel also has a 100 amp main breaker. Stupid question coming? Maybe. There is only 60 amps available in the barn, correct? Any problem with this other than the 100 amp breaker in the barn is misleading? Or is this common?
That would be my guess. You have a 60amp breaker feeding another subpanel which is only supplying 60amps. Totally a guess but that’s what I see.
Also, is that aluminum wire I spot, sheething on the wire cut back too far on the lug, no antioxidant?
Yes Sir! That is correct. 
Two words… “Weakest Link”.
3 Likes
Thumbs up, JJ. Your two words make it real easy to remember for the newbies. 
1 Like
Be happy they didn’t do it the other way and put a 100 amp at the panel and a 60 amp at the sub panel. With current loss over long enough run and insufficient wiring capacity, load on the wire could become excessive.
The feeder to the barn is 60 amps. The 100 amp main CB is the required disconnecting means for a separate structure. The black neutrals and EGC’s should be re-identified with white and green markings.
The sub feed appears to be 2awg aluminum. Rated for 100A. Please explain how it would be wrong if reversed? Frankly since the main is 100A, if I am correct that it is 2awg this panel could have been feed using subfeed lugs with no breaker at the service panel.
#2 AWG aluminum is only rated for 90 amps @ 75° C unless you can apply the 83% rule in 310.15(B)(7).
My response was made in general terms, where often someone puts a larger breaker in the panel than should be there due to circuit tripping and overheats the wiring. There was no definitive way to know what wiring gauge was installed based on viewing the picture on a mobile phone. So yes, in this case 60 amp breaker in the main panel is the weak link.
Very informative - thanks.