Journeyman Electrician Practice Exam

What is the minimum rating for a service disconnecting means for non-dwelling buildings with three 2-wire circuits?

1. 30 Amperes

2. 40 Amperes

3. 50 Amperes

4. 60 Amperes

The correct answer is: 60 Amperes

The minimum rating for a service disconnecting means in non-dwelling buildings that have three 2-wire circuits is determined by the total load that these circuits could potentially deliver. Each 2-wire circuit is typically rated at 15 or 20 Amperes, so with three circuits, the combined load capacity would range from 45 to 60 Amperes. To ensure safety and proper functionality, it's standard practice to select a disconnecting means rating that not only accommodates the total potential load but also provides a margin for demand factors and future load considerations. Therefore, a service disconnect rated at 60 Amperes ensures that it can handle the maximum load without tripping or failing under normal operating conditions, while still allowing for some additional capacity. This rating supports efficient operation and minimizes the risk of overloading the system, which is especially critical in non-dwelling buildings where equipment usage can be variable and often reaches high loads. Selecting a 60 Amp disconnect aligns with the need for reliability and enhances the capability of the electrical service in meeting demand without compromising safety.