Oklahoma Electrical Practice Exam

When must double lock nuts be used on rigid metal conduits?

1. When voltages exceed 120 volts to ground

2. When voltages exceed 240 volts to ground

3. When voltages exceed 250 volts to ground

4. When voltages exceed 480 volts to ground

The correct answer is: When voltages exceed 250 volts to ground

The requirement for using double lock nuts on rigid metal conduits is specifically tied to the safety and security of electrical installations. In this context, when voltages exceed 250 volts to ground, it becomes crucial to utilize double lock nuts to ensure proper mechanical grounding and to prevent loosening or accidental disconnection that could lead to hazardous situations. Double lock nuts provide a more secure connection than standard lock nuts, offering improved resistance to vibration and movement, which is particularly important in environments with higher voltage and potential electrical hazards. This requirement is framed within safety standards and codes, emphasizing the need for robust installations as the voltage levels increase. Thus, to maintain safety compliance and integrity in electrical systems, double lock nuts are mandated at voltages exceeding 250 volts to ground.