408.3(E) Phase Arrangement. 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.
Exception: Equipment within the same single section or multisection
switchboard or panelboard as the meter on 3-phase,
4-wire, delta-connected systems shall be permitted to have the
same phase configuration as the metering equipment.