According to NFPA 70, how is overcurrent protection typically measured?

Overcurrent protection is a critical aspect of electrical safety, and according to the National Electrical Code (NEC), which is encapsulated in NFPA 70, it is designed to protect conductors and equipment from damaging currents that exceed their capacity. Typically, overcurrent protection devices like fuses and circuit breakers are set to trip and interrupt the current when the load exceeds safe levels.

125% of the continuous load is the proper measurement because it provides an appropriate buffer for continuous loads, which are defined as loads that operate for three hours or more at their rated capacity. This 125% rule helps to ensure that the protection devices can handle temporary variations in current while effectively protecting the conductors from overload without nuisance tripping.

In contrast, setting overcurrent protection at just the load or at a lower percentage does not allow for this buffer, potentially leading to premature tripping during normal operation. Higher percentages, such as those represented in other choices, could risk the conductors overheating and failing without tripping the protective devices timely. Thus, adherence to the 125% threshold helps maintain safety and performance under normal operating conditions.