Table 310.15 B 16 question - 4/0 Cu for 200 amps

[Stevenfyeager]

In a 1979 office building, they have 4/0 Cu conductors for 200 amp service panel (single phase). It looks lile 3/0 would have been fine. Just a question for someone who does not do many commercial jobs. Thank you.

 

[augie47]

Several possibilities, could be a 60° conductor or 60° termination ratings. or voltage drop issue.
Likely just over-engineered.