This document provides specifications for various distribution boxes including dimensions, mounting sizes, and number of ways. Dimensions included are length, width. A distribution box is a low-voltage electrical enclosure that receives incoming power and distributes it safely to multiple outgoing circuits through protective and switching devices such as MCBs, RCDs, RCBOs, fuses, isolators, busbars, neutral bars, earth bars, and surge protective devices. The. Wiring diagram shows both PNP and NPN wiring. Dimensions are shown in mm (in. 81 ft)]. Plastic Electrical Box, also known as a consumer control unit or electricity control unit. Refer to catalogue appendix T17 for the definition and calculation of copper-related surcharges.