In today's step-by-step guide, we will demonstrate how to select the right size panelboard (whether it's a load center, distribution board, or circuit breaker panel) according to NEC and IEC standards, with worked examples. Related Post: How to Determine the Right Size . Choosing the correct electrical box dimensions is essential for safe wiring, code compliance, and long-term reliability. This guide explains typical wall-mount and floor-standing dimensions, how to read catalog sizes, and how to choose the right enclosure size for your layout. There is no single global chart for standard. Main Supply Electrical Distribution (ED) 1. Page 5 ED1 Lighting Timer and Contactor Box (for NW Tennis Courts). They help keep everything inside safe and working properly. Picking the right size matters.