Neutral and hots are all #6 awg. Looks like gnd was smaller.
With 75C (i.e. not NM) Cu #6 ungrounded (hot) conductors:
70A OCPD --good for loads up to 65A only--#8 Cu EGC
60A OCPD--#10 Cu EGC
50A OCPD--#8 Cu EGC (*)
[I don't make the rules, but yes, if you downsize the OCPD from 60A to 50A you are supposed to upsize the EGC.]
(*) Unless #8 ungrounded conductors wouldn't be large enough due to derating for temperature or number of current carrying conductors.
The wiring I believe was called #2/0 NM, it is the largest stuff I have seen, copper, which goes everywhere.
These stuff is protected by the 200 amp breaker in the main service panel.
NM cable maxes out at #2 Cu, which is only good for 95A.
Is your main service 200A only, not a 400A service with dual 200A disconnects? If so, then 2/0 Cu is sufficient for protection at 200A, and I'd say OK for 160A continuous (although it's arguably a grey area and could be construed to be limited to 140A continuous). Or 4/0 Al (same grey area, possibly only good for 144A continuous).
If it is a 400A (2x200A) service, then you would need 3/0 Cu, 2/0 Cu is too small and would require a 175A breaker. In Al you could still use 4/0, but it would be unambiguously limited to 180A of load, or 144A continuous.
Cheers,
Wayne
I forget the size of the neutral in the one subpanel he said. Much smaller than the feeds. Picture attached
The large white wire in that photo is connected to your neutral bar but is not part of the supply to that panel. The supply are the fat black, red, and black with grey stripe Aluminum conductors.
I'd need to know more about which wires are exiting each of the top two large holes at the top, and where they are going, but my first guess is that the white wire is associated with the two black wires on the 100A breaker at the bottom. In which case it is going out the wrong hole in the panel, it should exit via the same hole as the associated ungrounded (hot) conductors.
Of course that theory only makes sense if both of those holes go to the same enclosure. And the fact the 100A exit through the same hole as some NM
cables is a bit unusual, would be interested to see what is going on just above the panel.
BTW, if your electrician actually said to you "the white wire is too small compared to the big red wire" then they are pretty clueless about what they are looking at. If they said "the white wire is going out the wrong hole" that's correct. If they said "the white wire is too small compared to the wires on the 100A breaker" then that may or may not be true and would require a load calculation to decide.
Cheers, Wayne