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travellerw
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# Posted: 6 Mar 2022 18:37
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Ok.. I need some help with the whole grounding bonding thing..
In a standard house, I understand it quite well. There are 2 ground points (usually 1 rod and a pipe). The neutral and ground are bonded at the MAIN electrical panel.
However, in my system, I'm a little confused. I will have an inverter and a generator about 20 ft from the cabin. I will just feed 120V from either of those sources into the cabin (most likely with an autoswitch).
Where do I connect the ground? and where do I bond the neutral and ground? Is it at the generator and inverter? or do I do it at the breaker panel?
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neb
Member
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# Posted: 6 Mar 2022 18:46
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Ground at the breaker box. There should be an 8-foot rod driven there if not install one.
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travellerw
Member
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# Posted: 6 Mar 2022 18:49
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Quoting: neb Ground at the breaker box. There should be an 8-foot rod driven there if not install one.
That was my original plan (actually 2 rods 5M apart are code here)... but I'm unsure. My logic tells me the grounding and bonding should be at the source.
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Irrigation Guy
Member
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# Posted: 6 Mar 2022 19:07
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Tip for driving ground rods is to use a full size hammer drill. The rod will fit right in where the bit goes. It will make it a breeze.
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gcrank1
Member
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# Posted: 6 Mar 2022 19:09
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IDK!
But I read about this a lot trying to grasp it.
Lots on diysolarforum.com
Seems I remember that the 'floating neutral' of many generators and inverters makes it different than typical grid wiring.
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ICC
Member
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# Posted: 6 Mar 2022 20:32 - Edited by: ICC
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Depends on the generator and inverter.
Some cheaper inverters have an internal bond. Most often that will be any inverter that has a built in receptacle. Inverters that require hard wiring into a system usually will NOT have an internal bond.
Note: the absence of an internal neutral-ground bond is often referred to as being a "floating neutral".
Generators can be all over the place as far as bonds or no bonds go.
For example, Honda inverter generators all have a floating neutral, except for the biggest ones like the EU6500 and EU7000. There are some of the industrial EB series that DO have a bonded neutral.
Test the generator outlet. With the generator OF, use a multimeter set to read resistance ohms. Check between the ground terminal and the neutral (wide slot). If that measures at "OL" (open line) or 0.0 ohms that generator has a floating neutral.
One of those plug-in three-led testers can also be used to test. There are 2 amber and one red led. Plug it into the running generator. If only one amber led illuminates there is a floating neytral. If both amber lights illuminate, that generator has a bonded neutral-ground. Any other combination of lit leds indicates some other issue.
It gets more complicated when a transfer switch is used. Some transfer switches switch the neutral and others do not. Most transfer switches keep the neutral intact, so a floating neutral generator is perfect for those circumstances.
As for the actual grounds rods, plates or pipe at the house it is more logical to have all that at the service panel, but electrically it would work the same if the earth ground was at the other end of the house. Saves the electrician from running around trying to find the earthed rod.
It is easy to get confused on this when searching the web. If what one is reading is directed at generator use in an RV the answers can be different than when talking about plugging a house into a generator.
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travellerw
Member
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# Posted: 7 Mar 2022 09:37
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So.. If I'm understanding this right..
As long as the inverter or generator do not have a bonded neutral-ground, then I will be fine doing that at the cabin panel. If they do, then grounding at that location makes the most sense.
The generator I will be using this year definitely is a floating neutral but is a simple mod to bond it. I will test the inverter, but willing to bet its bonded.
I think doing it at the sources makes the most sense. I have a 9KW diesel industrial generator I will be installing in the future. I'm %99 sure it has a bonded neutral-ground.
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ICC
Member
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# Posted: 7 Mar 2022 18:07
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It is seldom (never?) a sure thing. When using a generator we did not know, we checked all the time. We often rented equipment and never trusted what they told us. Mostly, we never asked the rental company because we felt safer testing ourselves.
article of interest
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gcrank1
Member
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# Posted: 7 Mar 2022 19:39
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+that!
What personnel wherever 'thinks' is correct is often what they have been told, not tested or verified.
Im full in the camp of self verifying.
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travellerw
Member
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# Posted: 7 Mar 2022 21:09
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Turns out both the inverter and generator are not bonded.
I think I will drive 2 grounding rods at the cabin and ground it there. Then bond in the panel.
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paulz
Member
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# Posted: 10 Mar 2022 09:23
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What do you do on boats?
Since you've got it figured, I'll ask about mine. Cabin is all 12vdc, except the new inverter which has no grounding screw. I have a plug in cord running through the wall to an outdoor receptacle, so I can run a power tool without dragging an extension cord into the cabin. From there I ran romex through conduit to my shop, with an indoor receptacle there, to use when the shop solar bank is weak.
Do I need to ground those two receptacles?
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travellerw
Member
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# Posted: 10 Mar 2022 15:50
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Everything on boats is floating 
but seriously.. On most boats there is no "real" ground. As an example on our boat the only metal bits that exited the boat were our anchor chain and the 2 engine final drives. Both of those are poor conductors as they are painted.
For your scenario, you are technically relying on the inverter to be the circuit breaker. If it was me, I would definitely ground it.
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