Article 702.7(C) Power Inlet (Signs for Optional Standby Systems)

[Mr. Spinosa]

Is a portable generator (the type typically used by home owners when the power goes out) a separately derived system? Or, is it considered a nonseparately derived system? I have thought it was a separately derived system, but now I am unsure. - When the generator is plugged in, I would say there is a solid connection between the grounded conductors. Wondering which sign listed in Article 702.7(C) needs to go by the generator inlet.

 

[LarryFine]

Depends on the transfer switching mechanism that prevents the generator and primary source from being interconnected. If the neutral is unswitched, meaning remains interconnected, then the generator is not an SDS; if the neutral is switched, the generator is an SDS.

 

[infinity]

Setup as either an SDS or not you'll need signs at the service equipment (not the meter) {702.7(A)} and a sign at the inlet stating the type of system. {702.7(C)} Also as a non-SDS the neutral needs to be un-bonded in the generator.

 

[don_resqcapt19]

While few generators are listed, the UL Guide Information for "Engine Generators for Portable Use (FTCN)" says:

When a portable generator is used to supply a building or structure wiring system:

1. The generator is considered a separately derived system in accordance with ANSI/NFPA 70, "National Electrical Code" (NEC).​

2. The generator is intended to be connected through permanently installed certified transfer equipment that switches all conductors other than the equipment grounding conductor.​

3. The frame of a certified generator is connected to the equipment-grounding conductor and the grounded (neutral) conductor of the generator. When properly connected to a premises or structure wiring system, the portable generator will be connected to the premises or structure grounding electrode for its ground reference.​

4. Portable generators used other than to power building or structure wiring systems are intended to be connected to ground if required by the NEC.​

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