Ya'll will love this set up. In one of my schools I have a 208Y120 3 phase panel with a 100A main. Whenever we loose power this main trips when the power comes back on. It is fed from a 75kva xfmr about 4 feet from it (that calculates to 208 amps max). At some point in the past this was a 45 kva xfmr but it was replaced to handle the two new panels they put in the room about 4 feet to the other side of the new 75 kva xfmr. To feed these new panels they ran a pipe from the first panel to the second and an offset nipple between the second and third. Now the good part ... they attached the feed to the bottom of the bus bars in panel #1. The second panel also has a 100 amp main and #3 is fed from a 3P60 in panel #2. Needless to say we now have 3 panels controlled by the 100 amp main. As per my amprobe the load is ~85-90amp steady and they couldn't figure out why it trips when we slam 90 amps (120 circuits) on at the same time thru a 100 amp main. BTW: before the second and third panels were added, it never tripped.
Now the question: I can find no code violation in removing the feed between the panels and sending 100 amps from the xfmr to (each of) panels 1 & 2 directly. (100a to panel 1 and 100a to panel 2, leave 3 as a sub of #2) That would not exceed the 75kva and would take 1/2 the load off the main in panel 1. Assuming we size the conductors correctly can anybody tell me of any violation here?
