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Grounding a generator

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How should I earth ground a generator that I intend to use as my "a/c in" to my inverter when it's cloudy and my pv array is unable to charge my batteries? Can I use the same ground rod that my service panel os connected to or will I be creating a ground loop? Should I drive a separate ground rod and connect it separately? Is there a problem with having the generator separately grounded and it causing a ground loop because the service panel has a separate ground? This topic of earth grounds has my head spinning. Please help, you guys have been a great help with installing my solar system.
 
How should I earth ground a generator that I intend to use as my "a/c in" to my inverter when it's cloudy and my pv array is unable to charge my batteries? Can I use the same ground rod that my service panel os connected to or will I be creating a ground loop? Should I drive a separate ground rod and connect it separately? Is there a problem with having the generator separately grounded and it causing a ground loop because the service panel has a separate ground? This topic of earth grounds has my head spinning. Please help, you guys have been a great help with installing my solar system.


Not like this:

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If your generator is connected to your panel, and your panel N-G is bonded and connected to a ground rod, your generator IS grounded when connected to the panel.

IF you chose to drive a ground rod at your generator, you need to bond the generator and panel ground rods. Yes. Connect them with a wire.

I remember things this way:

In a system, all items above the ground need to be connected, and all items below the ground need to be connected with ONLY ONE connection between above and below.
 
If your generator is connected to an already grounded system, it should NOT have it's own ground. It should also not have neutral bonded to ground inside the generator. Check your generator manual, but for almost all generators, you take off the generator endbell, and physically disconnect the white wire from the green wire.

How is your generator wired into your inverter? In mine, I use a four-prong split-phase 240V plug that has L1, L2, N, and G. L1, L2, and N get connected to the ACin terminals of the inverter. The G connection leads from the generator plug to the main grounding bussbar inside the inverter's power center. So, my generator is grounded via the cable that connects it to the inverter.
 
If my distribution panel is not bonded, then I need the generator to be n-g bonded. Is this correct? I have a totally off grid system, so my service panel is not bonded. The inverter is n-g bonded, until I run the generator, then the inverter goes into bypass mode and opens the n-g bond. So if my distribution panel is earth grounded then my generator does not to be grounded separately. Is this correct? This earth grounding stuff is crazy. You guys are a great source of info.
 
What kind of generator? I think the larger whole house ones do that automatically when the grid is down. But I’d have to look that up.
 
It's an open frame 8750 watt inverter gen. That is connected to my inverter using a 30 amp four prong plug.
 
The inverter is n-g bonded, until I run the generator, then the inverter goes into bypass mode and opens the n-g bond. So if my distribution panel is earth grounded then my generator does not to be grounded separately. Is this correct? This earth grounding stuff is crazy. You guys are a great source of info.

When the N-G bond in the inverter (which should be the only N-G bond in the system while inverter is on), when that inverter goes into bypass and opens the N-G bond via its relay, now there would be no other N-G bond, so the generator would then be considered a 'separately derived system', and so in that case, the generator can no longer be treated as an appliance, and needs to be grounded to the rod and also N-G bonded (not all generators are N-G bonded from factory, have to check).
 
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Another way to understand it, is in many cases when an inverter is wired into a house on the grid say, it may be getting its input AC connection from a breaker panel which is N-G bonded, so when that inverter is running in bypass, it is essentially considered that the main breaker panel service is the power source, and thus is the location where the N-G bond is being provided (to the critical loads breaker panel and all its circuits).

Once the inverter is turned on and it flips the relay to disconnect the AC input and create its own N-G bond, it is now the power source for the critical loads panel.

I suppose if the generator is not already N-G bonded, one could also just install a small double-pole single breaker box ahead of the inverter AC input, dedicated for the generator to plug into, make an N-G bond there in that box (with connection to ground rod), and then the generator would plug into that as an appliance and be considered a 'non-separately derived system'... (and would need to confirm the generator does not have its own N-G bond already in it, and is not connected to a ground rod).

This way, if the generator has a short to ground, the current would travel through the ground wire of the power feed cable and into the little breaker box, and go to ground where the N-G bond connection is, which also has the connection to the ground rod.

More ref:
 
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The inverter is n-g bonded, until I run the generator, then the inverter goes into bypass mode and opens the n-g bond. So if my distribution panel is earth grounded then my generator does not to be grounded separately.
I think part of the problem here is using the phase "bypass mode". Is that actually what is happening with your inverter? With the way my inverter is wired, bypass means completely bypassing the inverter so electricity is flowing directly to the main panel from the grid or the generator which is going to ACout. My generator is wired into ACin. So, generator power to my inverter is NOT being bypassed. In that case, the generator is supposed to be grounded at the panel
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That all makes sense. I have checked on my generator and the manufacturer assured me that it is n-g bonded. In fact they have a procedure in their manual for breaking the n-g bond to turn it into a floating neutral set up. My question is when I hook up my generator to my system which is already earth grounded, why do I need to use another earth ground? And if I would separately ground my generator would that set up a ground loop situation, that would be dangerous?
 
If you don't have an N-G bond, your system isn't earthed... just the ground wire is.

When running on generator, if:

your generator is N-G bonded
your inverter breaks its N-G bond when AC-in is active
your AC panel has no N-G bond
your ground is earthed

You're good.

You need no additional grounding/bonding/earthing.
 
Thank you all for your patience and help in this project. You guys have made this install possible.
 
Just adding another data point. I'm doing a similar installation, using a 24kw Generac whole house unit. It has instructions to do the N-G bond at the generator (if needed), but does not come that way from the factory. I believe they recommend N-G bonding at the transfer switch.
 
Just adding another data point. I'm doing a similar installation, using a 24kw Generac whole house unit. It has instructions to do the N-G bond at the generator (if needed), but does not come that way from the factory. I believe they recommend N-G bonding at the transfer switch.

Yeah great advice. Just to add though, if you are off grid and don't require an auto transfer switch pre-inverter, then you could just put a little mini single 2-pole breaker panel there instead, dedicated for the generator circuit, where the N-G bond (for running in inverter bypass) could be made (as long as there is no N-G bond in the generator itself).

Then when the inverter is running, theoretically its own internal ATS circuit should be disconnecting from the AC input's neutral, so it wouldn't see that N-G bond coming from the input side (provided by the mini breaker panel), for whenever it was being the active unit making the N-G bond.

Of course, whether your running with N-G bond at generator, or having it made in a pre-inverter panel or an ATS, I would recommend at any rate to check on my specific inverter (in bypass, and while running on inverter) to make sure how it is handling the AC input neutral (in both operating modes), before I rolled out any production solution.

If the AC input of the inverter was still keeping the AC input neutral connected while inverting, one might need a relay on the input neutral to make the neutral go open from the AC input (anytime the inverter is turned on), so as not to have two N-G bonds at same time.

Or one could even have a 3-pole breaker with a neutral in the generator mini-panel, and manually shut it off when the inverter is running, to ensure that N-G bond is broken (the one going into the inverter AC input) while the inverter is inverting and it's providing the N-G bond.

You could also use an ATS instead of a mini-panel, set up using only the generator input (with other input empty), and when the generator turns off, the ATS relay turns back to NC side, would just be hooked to nothing, which would break the N-G bond being provided.

But my suspicion is that most inverters which have a built-in ATS, are going to disconnect neutral on their AC input (while inverting), since it is assumed that they are always being provided power via a native N-G bond upstream from that input, as many normal grid installations would have that attached to the AC grid input that is always live (when not off-grid)...
 
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