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<p class=MsoNormal><span style='color:#1F497D'>The problem of the bonded
chassis in most generators has been with us for years, and there is no real
solution. With most cheap (and ubiquitous) portables, the AC neutral is
internally bonded to the chassis and can’t be easily undone. When I
wrote the HP generator article I attempted to address this issue without
getting too technical. I ran this specific issue by John Wiles for his advice,
and the final wording reflected his position that the AC ground loop –
that is, maintaining the neutral-ground bond in both the generator and the
inverter system and accepting that the ground conductor would carry a portion
of any current otherwise being carried on the neutral – was the best of
the options. <o:p></o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal style='margin-left:.25in;text-indent:-.25in;mso-list:l0 level1 lfo2'><![if !supportLists]><span
style='font-family:Symbol'><span style='mso-list:Ignore'>·<span
style='font:7.0pt "Times New Roman"'>
</span></span></span><![endif]><span style='color:#1F497D'>The final wording as
submitted to HP was: “</span><span style='font-family:"Calibri","sans-serif"'>Quality
generators allow the neutral conductor to either connect to the generator
chassis (for prime power application) or remain separate from it. Portable
generators are seldom properly grounded, so manufacturers ground the neutral
output conductor to the chassis. When connected into a grounded power system,
however, this presents a safety hazard, as the neutral is now bonded to the
ground at two places—one in the power system AC and one in the
generator—and the safety ground wire becomes current-carrying. Some units
also include AC ground-fault protection, which is incompatible with connection
to a grounded power system. There is no simple, Code-compliant solution
to this. The safest noncompliant approach is to bundle an insulated green
ground conductor with the power conductors between the generator and the main
ground buss, to both ground the chassis and minimize shock potential.”<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'><o:p> </o:p></span></p>
<p class=MsoNormal>Inherent in this is that that grounding conductor between
gennie and ground buss be bundled in conduit and boxes, rather than being left
bare or exposed, as would otherwise be OK with any grounding conductor.<o:p></o:p></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<div>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>Allan Sindelar<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;color:#1F497D'><a
href="mailto:Allan@positiveenergysolar.com">Allan@positiveenergysolar.com</a></span><span
style='font-size:11.0pt;color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;color:#1F497D'>NABCEP
Certified Photovoltaic Installer</span><span style='font-size:11.0pt;
color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;color:#1F497D'>EE98J
Journeyman Electrician</span><span style='font-size:11.0pt;color:#1F497D'><o:p></o:p></span></p>
<p class=MsoNormal><b><span style='font-size:11.0pt;color:#1F497D'>Positive
Energy, Inc.<o:p></o:p></span></b></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>3201 Calle
Marie<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>Santa Fe, New
Mexico 87507<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;color:#1F497D'>505 424-1112<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;color:#1F497D'><a
href="http://www.positiveenergysolar.com/">www.PositiveEnergySolar.com</a></span><span
style='font-size:11.0pt;color:#1F497D'><o:p></o:p></span></p>
</div>
<p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal>Larry,<br>
Sounds like there are two neutral ground bonds: one at the generator and one at
the house. This causes part of the neutral current to flow on the ground
- a guaranteed way to trip the GFI. This is the catch 22 of connecting a
portable generator, or one with an outlet, to a house system. The house
panel has to have a neutral ground bond. The generator also has to have a
neutral ground bond (Although the small Honda and Yamaha inverter generators
don't. How do they get away with that? - No exposed metal to touch I guess.) or
the GFI won't work and ground faults won't trip the generator output breakers.<br>
<br>
Solutions (unfortunately none of these may be suitable and they all have
potential problems):<br>
<br>
Permanently wire the generator. On the generator, remove the
neutral/ground bond and remove all of the electric outlets. In some
locations, you aren't allowed to permanently wire a generator unless it is U/L
listed. And most (maybe all) portable generators aren't U/L listed.<br>
<br>
Replace the GFI outlet with a non-GFI outlet (so it will be like the old
Homelight generator). Part of the neutral current will flow on the ground
wire. That's a code violation, but for 20 and 30-amp outlets the ground
wire has adequate ampacity so nothing is going to overheat. In fact, even
6 AWG SO cord has a ground wire the same size as the conductors.<br>
<br>
Use a 2-prong cheater. This will prevent the GFI from tripping. It
also prevents any ground fault past the cheater from returning to the
generator. It's probably best to locate the cheater at the load end of
the cord; that way if the cord is damaged the GFI will still trip. If
there is ground fault past the cheater, there will be one or probably more than
one locations where there is shock hazard. If you touch the generator
frame, it'll tingle; if the ground is wet, it might be severe.<br>
<br>
Use a mobile-style inverter that will switch the neutral/ground bond.
Most of these are not U/L for house wiring. I think this is the best
solution but it doesn't cover the circumstance of a grid backup inverter
connected to a portable generator.<br>
<br>
See. I don't have any good solutions.<br>
<br>
Kent Osterberg<br>
Blue Mountain Solar<o:p></o:p></p>
<pre> <o:p></o:p></pre></div>
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