A floor-mounted assembly of one or more enclosed vertical sections having a horizontal common power bus and principally containing combination motor control units. These units are mounted one above the other in the vertical sections. The sections normally incorporate vertical buses connected to the common power bus, thus extending the common power supply to the individual units. Power may be supplied to the individual units by bus-bar connections, by stab connection, or by suitable wiring (as defined in NEMA Standard Pub. No. ICS 2, 1988).