NEC Commercial Electrical Practice Test

In dwelling units, what must be provided to disconnect all ungrounded conductors on a multi-wire branch circuit?

1. Separate switches

2. A single disconnect

3. Individual fuses

4. Grounding rods

The correct answer is: A single disconnect

In dwelling units, providing a single disconnect for all ungrounded conductors on a multi-wire branch circuit is essential for safety and compliance with code. A multi-wire branch circuit typically consists of two or three ungrounded conductors sharing a common neutral. Since these conductors can be energized, it's crucial to ensure that all ungrounded conductors can be de-energized simultaneously to avoid hazards during maintenance or repair work. Using a single disconnect allows for the quick and complete shutoff of electrical supply, which protects individuals working on the circuit from potential shock or electrical hazards. This is in accordance with the National Electrical Code (NEC), which emphasizes the need for a means to safely disconnect electrical circuits. A single disconnect approach is often preferred as it simplifies the disconnection process compared to using separate switches or individual fuses, which can lead to confusion and risk if not properly labeled or coordinated. Other options, such as separate switches or individual fuses, might not achieve the same level of safety, as they may not ensure that all conductors are disconnected at the same time. Grounding rods are unrelated to the disconnection of ungrounded conductors and focus more on providing a path for fault current to the earth. Therefore, the