Does a generator need to be grounded as a separately derived system if its transfer switch switches the grounded conductor?

A generator does not need to be grounded as a separately derived system if its transfer switch switches the grounded conductor. This principle is grounded in the definition of a separately derived system, which requires that the source is capable of producing a grounded neutral. Since the transfer switch is designed to switch the grounded conductor, it indicates that the generator will not create a separate grounding system. Therefore, the existing grounding at the service is adequate, and the generator operates under the protective measures already in place from the premises' electrical system.

In scenarios where the system is not a separately derived system, grounding requirements are typically met through the existing service equipment, thus eliminating the need for additional grounding for the generator. This understanding aligns with electrical codes that emphasize the importance of maintaining safety and proper grounding practices without unnecessary duplication of grounding systems.