Speaking of standards, NBR 5410 is ABNT's specific norm that mentions the necessary distance for junction boxes. These rules define when you must install a box, how large it must be, how you must install it, and how inspectors evaluate compliance. This guide breaks down the actual rules inspectors check — with calculations and. When installing insulated conductors of 4 AWG or larger, the minimum dimensions of pull or junction boxes installed in a raceway or cable run must comply with 314. The NEC provides sizing requirements in 314. Keep in mind these. stallation and use of boxes. The article includes table references that guide the electrician in the selection of the proper box size necessary to safely accommodate ele trical service requirements. The box capacity table shown (page A-5) is reproduced in part from the NEC® as a quick reference and.