Genset wiring issues

Most of us just fire up the genset and plug in. Every now and then someone wonders about whether it would be a good idea to provide an earth ground or whether the wiring is the way it should be. John Grzywacz runs through the wiring codes and their rationales in his paper Portable Generators and OSHA Construction Regulations (PDF).

The recommendation is against earth grounding as that just provides another electrocution hazard with a portable genset.

Ground fault interrupters used to not be required but that exemption seems to have been dropped in the NEC. Three factors are considered by OSHA. These are 5kW or less, 2 wire single phase, and no connection between the frame and the circuit wires. Because OSHA and NEC have different ideas, there may be some confusion. It is likely that the trend is towards GFI in all cases.

The third issue is the neutral and frame ground bonding. It appears that the NEC requires the connection for any genset, like an RV genset, that is not otherwise connected to any power system. This issue seems to have caused some differences in how the popular Honda 2000i is wired between Canada and the U.S. Note also that bonding the neutral and frame ground would eliminate one the three conditions necessary for the GFI exemption.

Grzywacz explains the why of these issues and that can help you understand what is going on with your genset.

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