Re: NFPA petition decision on 2014 NEC 445.20, for portable generators <15kW
That the NFPA finally relented and grandfathered generators manufactured before 1/1/2015 (as long as they are used with separate GFCIs) pulled us back from the brink of disaster, NEC 445.20, as written, may still spell doom for the Honda EU6500 as well as the new EU7000. If you follow the argument by the Technical Director of the PGMA in TIA 1117 that was voted into the 2014 Code, NEC 445.20 in its final form “would allow the continued use of existing portable generators by allowing the use of external GFCI devices to provide equivalent protection.” This spells doom for the Honda EU6500 and the new EU7000 because, without Bonded Neutrals, separate GFCIs will not provide “equivalent protection” on these generators.
Tests recently conducted by The Construction Safety Association of Ontario (CSAO) uncovered significant problems in using GFCIs on portable generators with Floating Neutrals. Since the CSAO conducted their tests to determine the effectiveness of GFCIs used on portable generators in typical construction scenarios, they did not test the EU6500 directly, but their findings are applicable to it. The GFCIs used in the CSAO tests were the very portable use cord sets that incorporate listed GFCI protection for personnel described in NEC 445.20. In the tests a rheostat was used to simulate a current leak to Ground (Ground Fault). Generators connected to GFCIs were tested on wet ground, dry surfaces, and an insulated surface (the back of a pickup truck). In addition, tests covered variable grounding conditions: proper earth ground, earth ground with some resistance, no earth ground. Based upon their tests, the CSAO report drew the following conclusions (use this link for the complete report):
1) In the case of Floating Neutral generators, where the Neutral is not bonded or grounded but "Floating", GFCIs failed to trip even when the current leak reached higher than acceptable levels. Without a Neutral bond, electricity did not leak to ground to trip the GFCI - creating a possibly hazardous situation in the event of a second Fault if the GFCI is not located properly in the distribution system.
2) GFCI test buttons functioned regardless of the GFCI's operability. The buttons cannot be used to test the effectiveness of GFCIs or grounding.
3) Proper placement of GFCI protection is different for Floating Neutral and Bonded Neutral generators.
The CSAO report author concluded that simply using a GFCI on a Floating Neutral generator will not ensure a safe system, and can in fact be misleading. That is because a GFCI will not operate reliably if one side of the winding is not bonded to the generator frame. Without a bond Fault Current has no path back to the winding to complete the circuit. Only when Neutral is bonded to Ground, will current go to Ground to complete the circuit when there is a current leak. In other words, a complete circuit is required to create an imbalance and cause the GFCI to trip.
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GFCI test circuits are misleading when they are used on Floating Neutral generators because they can produce a false positive. On a Floating Neutral generator, the test button will draw power from the Hot through the CT and back through the CT again to the Neutral via a Current Limiting Resister. The discrepancy caused by the Current Limiting Resister in the test circuit (illustrated above) will initiate the GFCI to trip even though there is in fact no Ground Fault Circuit for Fault Current to go to if there were a Fault. The false positive received by GFCI test circuits on ungrounded Floating Neutral generators does nothing to eliminate faulty equipment.
Where separate GFCIs will clearly not provide “equivalent protection” on the EU6500, it does not qualify for the exemption to NEC 445.20 that requires that “All 125-volt, single-phase, 15-and 20-ampere receptacle … either shall have ground-fault circuit-interrupter protection for personnel … or shall not be available for use when the 125/250-volt locking-type receptacle is in use.” This spells doom for the single phase Honda inverter generator because what good is a generator that can’t supply both 120V and 240V at the same time.
Guy Holt, Gaffer
ScreenLight & Grip
rentals@screenlightandgrip.com
