Start by finding the total load for each circuit. For single-phase, use P = V × I. Always use the 80% rule for loads that run all the time. This keeps your box safe. Pro Insight: A well-planned distribution box feels like a silent partner—you only notice it when something's wrong. Our goal? Make sure you never notice it. 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. Professional electrical panel schedule tool for creating detailed load distributions, calculating circuit loads, balancing phases, and ensuring NEC compliance for electrical distribution panels. Panel schedules are essential for electrical system documentation, load analysis, and NEC compliance. What size distribution box do you need for a house? How do you know which circuit breaker to use? Can you add more breakers later? Why do you need GFCI or AFCI breakers? Choosing the right size and setup for your distribution box keeps your electrical system safe and working well. Power Supply is 430V (P-P), 230 (P-N), 50Hz. Branch Circuit-1: 4 No of 1Phase. When the electric box is only a lighting electric box or a small power, and the incoming line is less than 10 square, if the number of switch digits is less than 20, the width of the switch is added and 20mm on each side is the width of the electric box, and the height is the switch height Add.