Larry,
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.
Solutions (unfortunately none of these may be suitable and they all
have potential problems):
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.
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.
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.
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.
See. I don't have any good solutions.
Kent Osterberg
Blue Mountain Solar
Larry Brown wrote:
Dave,
The original setup was an 1800 watt Homelite generator with two non GFI
receptacles, no twist lock receptacle
The client had the generator from building their house
It was wired through a fused disconnect to the VFX3524
All worked fine
They tried the same set up with the new Generac 8000 watt inverter
They plugged into a 20 amp GFI receptacle on the generator and it kept
popping the GFI breaker
I did lower the Battery charger AC amps and the AC amps in but it
seemed to make no difference
Larry
On Nov 10, 2009, at 8:22 PM, David Palumbo wrote:
Larry,
Are you sure it is not a simple overload situation? Have you tried
reprogramming the VFX with a Mate to lower critical values (AC Amps In,
and
Battery charger AC amps)?
Seems strange a 8kW generator to have a 20A breaker protect a load like
a
generator (unless you were plugged into that outlet). How do you have
the
output wired?
Dave
-----Original Message-----
From: re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Larry
Brown
Sent: Tuesday, November 10, 2009 7:11 PM
To: RE-wrenches
Subject: [RE-wrenches] generator
Fellow Wrenches,
On an off the grid system we did for a client a year or two back, we
installed an Outback VFX3524 mounted on a Midnight Solar E Panel.
They had a manual pull Homelight generator as back up. All worked
well.
Recently the client upgraded to an electric start 8000 watt Generac
generator.
Now every time they start the new generator, the GFI 20 amp
receptacle on the generator pops.
There is probably a redundant neutral to ground bond that is causing
this but I am uncertain on the best approach to remedy this condition
Any recommendations or experience on how to get the generator to
interface with the system?
Thanks
Larry
Larry Brown
Sun Mountain
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