Small commercial: 20000 A sockets; allowance for lever-bypass and larger knockouts. Multi-tenant: stackable meter centers, modular widths/heights. Pro Insight: A well-planned distribution box feels like a silent partner—you only notice it when something's wrong. Before we dive into calculations, let's get familiar with a few essentials: 1. Your Project's Total Power Demand This isn't just adding up. These boards usually handle 120/240V single-phase power and support up to 400 amps. Plug-on breakers are common, making setup and repairs simple. The depth of multi-gang boxes also. Part (1) of Section 370-16 (a) describes in detail the method of counting wires, as well as clamps, fittings, or devices (i.