Which NEC articles cover load calculations for feeders and service equipment?

• A. Article 220 for load calculations; Article 215 for feeders
• B. Article 210 for receptacle spacing; Article 230 for service
• C. Article 300 for wiring methods; Article 334 for NM
• D. Article 430 for motor protections; Article 220 for load calculations

Answer: (A)

The key idea is that the NEC uses specific articles to guide how you calculate and size the loads that feeders and service equipment must carry. The rules for calculating the actual load the system must support are found in Article 220. This is where you determine the expected electrical demand for the building, including general lighting, small-appliance circuits, outlets, and other connected loads, using the applicable demand factors and standards.

Once you know that calculated load, you size the feeders to carry it, which is covered in Article 215. This article tells you how to apply the calculated load to determine appropriate conductor sizes and overcurrent protection for feeders, taking into account factors that affect how much current the feeders must handle between the service equipment and the distribution points.

Service equipment sizing is tied to these calculations as well, because the service disconnects and equipment must be rated to handle the calculated load, and Article 220 provides the foundational calculation framework that Article 215 then uses to specify feeder sizing. While other articles cover wiring methods, receptacles, or motor protections, they don’t address the load calculation framework or the specific sizing rules for feeders and service equipment.

So, the combination of Article 220 for load calculations and Article 215 for feeders is what governs sizing for feeders and service equipment.