A continuous duty load must not exceed what percentage of the circuit's capacity?

In electrical systems, continuous duty loads are defined as loads that are expected to operate for three hours or more. To ensure safety and reliability, it is crucial to adhere to capacity guidelines. The National Electrical Code (NEC) specifies that continuous duty loads should not exceed 80% of the circuit's capacity.

Using up to 80% of the circuit’s capacity for continuous loads allows for a safety margin, accommodating potential increases in load and avoiding overheating of circuits and conductors. This approach helps prevent tripping circuit breakers and reduces the risk of conductor insulation failure, which can occur due to overheating.

This guideline is particularly important when designing and assigning electrical loads, as exceeding this threshold could lead to equipment failure, reduced lifespan of electrical components, and safety hazards. Therefore, adhering strictly to this 80% rule for continuous loads is essential in load calculations for feeders and services.