NEC 408.3.E reads as follows The phase arrangement on 3-phase buses shall be A, B, C from front to back, top to bottom, or left to right, as viewed from the front of the switchboard or panelboard. The B phase shall be that phase having the higher voltage to ground on 3-phase, 4-wire, delta-connected systems. Other busbar arrangements shall be permitted for additions to existing installations and shall be marked. Have I missed the boat on this? A 3-phase system with a higer voltage on phase B than on phases A and C? I don't understand this. I thought a 3-phase system was, barring unbalanced impedances, balanced. What did I miss here?