Inverter grounding - avoiding ground loops, etc
I am in the final stages of installing a Xantrex Prowatt SW inverter. The inverter will be hardwired into the coach's AC system through a transfer switch (the other AC source is shore power and is wired into the other switch input).
This inverter has its AC neutral permanently bonded to AC ground.
The in addition to its 3-prong AC out, and DC +ve and -ve in, the inverter has a "chassis ground" screw. The manual says this should be connected via a (preferably green) 8 AWG wire to the vehicle chassis.
I'm struggling to understand the purpose of this wire, and whether it is appropriate on my system, and if it is, if wiring it to the battery negative is just as good as the chassis.
What I'm confused about is that this chassis ground seems internally bonded in the inverter to the AC ground and AC neutral. On my vehicle, the AC ground is already electrically connected to the chassis (at least according to a continuity tester). Since AC ground is connected to this grounding terminal on my inverter, won't adding a grounding cable to the chassis create a ground loop?
Similarly, the DC -ve of my coach's electrical system is already connected to the chassis (as I expect is normal/required on RVs). Hence, can't I ground this cable to the DC battery negative, rather than the chassis? Those two are electrically connected already, so the only question is that of how current will flow in the various failure modes:
It seems like for DC-side failure, the ground-to-battery-negative connection is strictly better, as that is the most direct return path so keeping the chassis out of it is useful.
For an AC-side failure, it is less clear, since I don't even know how the ground wire helps here. It seems like the return path is back to the inverter, and whatever AC-side fuse or breaker exists there should kick in.
I've searched quite a bit, but I don't find any consistent advice.
This inverter has its AC neutral permanently bonded to AC ground.
The in addition to its 3-prong AC out, and DC +ve and -ve in, the inverter has a "chassis ground" screw. The manual says this should be connected via a (preferably green) 8 AWG wire to the vehicle chassis.
I'm struggling to understand the purpose of this wire, and whether it is appropriate on my system, and if it is, if wiring it to the battery negative is just as good as the chassis.
What I'm confused about is that this chassis ground seems internally bonded in the inverter to the AC ground and AC neutral. On my vehicle, the AC ground is already electrically connected to the chassis (at least according to a continuity tester). Since AC ground is connected to this grounding terminal on my inverter, won't adding a grounding cable to the chassis create a ground loop?
Similarly, the DC -ve of my coach's electrical system is already connected to the chassis (as I expect is normal/required on RVs). Hence, can't I ground this cable to the DC battery negative, rather than the chassis? Those two are electrically connected already, so the only question is that of how current will flow in the various failure modes:
It seems like for DC-side failure, the ground-to-battery-negative connection is strictly better, as that is the most direct return path so keeping the chassis out of it is useful.
For an AC-side failure, it is less clear, since I don't even know how the ground wire helps here. It seems like the return path is back to the inverter, and whatever AC-side fuse or breaker exists there should kick in.
I've searched quite a bit, but I don't find any consistent advice.
