In just a few steps you will find the wiring and assembly plan, including complete documentation in accordance with standards. This is the design philosophy which the browser-based distribution board configurator from Eaton is based on. Proper setups ensure balanced electrical loads, ground fault protection, and easy maintenance. Common configurations include single-phase for homes and three-phase for. Summary: The National Electrical Code explains the Maximum Number of Wires that can be installed into a box, otherwise known as Box Fill. This code is based upon the type of box, wires, wire sizes, wire clamps and conduit fittings.