What is the purpose of load calculations (Article 220)?

• A. To determine color of conductors.
• B. To calculate energy efficiency.
• C. To size service equipment and feeders based on connected loads and demand factors.
• D. To size only the main disconnect.

Answer: (C)

The main idea behind load calculations is to determine how much current the service and feeders must be able to carry by summing up the expected connected loads and applying the demand factors described in Article 220. This approach reflects that not all loads operate at the same time, so the calculated load represents a safe, practical maximum that the electrical system should be able to serve. By using this calculated load, you size the service equipment and feeders with enough ampacity to handle normal operation, including continuous loads that must be accounted for at 125% and the diversity of noncontinuous loads. This sizing helps prevent both undersizing, which can cause overheating or nuisance trips, and oversizing, which wastes material and money. The main disconnect is part of the overall system, but the purpose isn’t to size just the disconnect in isolation; it’s to size the entire service and feeders to the calculated demand. Color of conductors and a separate focus on energy efficiency are not what load calculations determine.