New York State Master Electrician Practice Exam

Which of the following is true regarding multi-wire branch circuits?

1. They use a single circuit breaker for protection

2. They must be on the same phase

3. They can supply multiple circuits

4. They require separate neutral conductors

The correct answer is: They must be on the same phase

The correct understanding regarding multi-wire branch circuits highlights that they must be on the same phase to function correctly. In a multi-wire branch circuit, two or more circuit conductors share a single neutral conductor. Each of the hot wires must come from the same phase to ensure that the loads balanced and to minimize the risk of overloading the neutral. When two or more circuits share a neutral, it is crucial that they are on compatible phases to prevent any unintended current from exceeding the neutral’s capacity, which can lead to dangerous overheating. The other options do not accurately reflect the characteristics of multi-wire branch circuits. For example, it is common practice to use separate circuit breakers for each phase to maintain proper circuit control and safeguarding. They are designed to supply multiple circuits; however, this is within the limitation of being on the same phase. While multi-wire circuits can use a single neutral conductor—this simplifies wiring—it is not mandatory that separate neutral conductors are used, as shared neutrals are a standard feature of this circuit design. Understanding these principles is essential for ensuring electrical safety and compliance with the National Electrical Code (NEC).