Continuous loads are calculated at what percentage of the maximum current rating of the overcurrent device?

Continuous loads are specified to be calculated at 80% of the maximum current rating of the overcurrent device. This requirement is established in the National Electrical Code (NEC) guidelines, which aim to ensure safety and reliability in electrical systems.

When a circuit is designated for continuous loads, it is defined as a load where the maximum current is expected to persist for three hours or more. To avoid overheating and to provide a safety margin, the NEC mandates that continuous loads should not exceed 80% of the rated capacity of the circuit conductors and overcurrent protection devices. This practice ensures that the system can handle the load without risk of tripping overcurrent protection devices and permits a buffer for variations in current draw.

Thus, calculating continuous loads at this percentage helps in designing efficient and safe electrical systems, protecting both the equipment and the users from potential overloads that could lead to equipment failure or fire hazards.