HOLT Electricians Practice Exam

Overloads should be rated from what percentage?

1. 100%

2. 110%

3. 115%

4. 120%

The correct answer is: 115%

Overloads in electrical systems are typically rated from 115% of the full-load current for motors and other equipment. This 115% rating allows for a slight buffer beyond the operational capacity of the equipment, ensuring that the system can handle temporary overload conditions without tripping a protective device unnecessarily. Using a 115% rating helps to balance safety and efficiency, as it provides the necessary tolerance to account for the inrush currents that may occur when motors start or when equipment has brief periods of higher demand. This limit is in line with the National Electrical Code (NEC) guidelines, which are designed to protect both the equipment and the electrical infrastructure. While other percentages like 100%, 110%, or 120% may have applications in specific contexts, they do not offer the same level of protection and efficiency for general use. A 100% rating would not account for any overload, while 110% and 120% may trigger protective devices too frequently or risk overheating and damaging equipment. Therefore, 115% is considered the appropriate standard for overload ratings.