Inverter ground to neutral issue

[electricthot]

I am off grid, and am attempting to integrate a Honda EU3000is inverter/generator into my system, connecting it directly to my inverter (Freedom X 2000), which has switching capability between battery bank or grid/generator, and makes the GN bond internally when only battery power is available. But when grid/generator power is present, it removes the GN bond, and since there is no GN bond in my Honda, does this leave me with a floating ground, and is this ok? My inverter makes this connection internally when my battery bank is the only power source present. But if another source, a generator or the grid is present, the GN bond is removed. I should mention my battery (system) neg is earth grounded.

 

[MrThisIsME]

Common problem. You can bond the ground to neutral yourself or just buy one of the ready made plugs.

https://www.amazon.com/gp/product/B08HZGMRB1/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[John Frum]

But when grid/generator power is present, it removes the GN bond, and since there is no GN bond in my Honda, does this leave me with a floating ground, and is this ok?

Yes it leaves you with a floating neutral which means your system can't clear a ground fault under typical conditions.
Is there an ac distribution panel downstream from inverter?

 

[electricthot]

Common problem. You can bond the ground to neutral yourself or just buy one of the ready made plugs.

https://www.amazon.com/gp/product/B08HZGMRB1/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I would prefer to keep the switching completely automatic. When I start the generator, the inverter will switch without interuption. I don't want to take a chance and forget to disconnect that manually placed GN connection when I shut the generator off, not to mention if it ran out of gas with that gn bond in place. My inverter would then have two GN bonds.

 

[John Frum]

I would prefer to keep the switching completely automatic. When I start the generator, the inverter will switch without interuption. I don't want to take a chance and forget to disconnect that manually placed GN connection when I shut the generator off, not to mention if it ran out of gas with that gn bond in place. My inverter would then have two GN bonds.

A proper ATS=automatic transfer switch makes the bonds mutually exclusive.

 

[electricthot]

Yes it leaves you with a floating neutral which means your system can't clear a ground fault under typical conditions.
Is there an ac distribution panel downstream from inverter?

No. Are you suggesting another switching mechanism for the GN bond when running off the generator? Actually, the gfi issue doesn't matter, and this mode of operation will just be a backup source. Just need to understand what it means to have a floating ground and how does it effect my system.

 

[Hedges]

Common problem. You can bond the ground to neutral yourself or just buy one of the ready made plugs.

https://www.amazon.com/gp/product/B08HZGMRB1/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Or make a cord for input of inverter to be plugged into generator. Do the N/G bond in the cord.

I would prefer to keep the switching completely automatic. When I start the generator, the inverter will switch without interuption. I don't want to take a chance and forget to disconnect that manually placed GN connection when I shut the generator off, not to mention if it ran out of gas with that gn bond in place. My inverter would then have two GN bonds.

A proper ATS=automatic transfer switch makes the bonds mutually exclusive.

That manual extra ground is on input of inverter, not output. So inverter serves as ATS, makes bonding exclusive.

I suggest in a cord, not a shorting plug, because that associates it with inverter input, doesn't get carried with generator.
(but if using generator portable, may want to ground to a ground rod and bond neutral. Portable generator tends to be floating neutral. Actually, you want an all-pole GFIC.)

 

[John Frum]

Are you suggesting another switching mechanism for the GN bond when running off the generator?

No just trying to acertain your topology to make an informed recommendation.

Actually, the gfi issue doesn't matter, and this mode of operation will just be a backup source.

I'm not talking about GFCI=ground fault circuit interrupter.
GFCI opens the circuit on a mismatch between the current tally on the hot wire and the neutral.
No grounding conductor is even required.

Just need to understand what it means to have a floating ground and how does it effect my system.

The neutral/ground bond allows ground fault current(traveling on the green wire) to get back on the neutral wire to complete a low impedance circuit thereby tripping the over-current protection device and thus clearing the fault.

 

[electricthot]

Or make a cord for input of inverter to be plugged into generator. Do the N/G bond in the cord.





That manual extra ground is on input of inverter, not output. So inverter serves as ATS, makes bonding exclusive.

I suggest in a cord, not a shorting plug, because that associates it with inverter input, doesn't get carried with generator.
(but if using generator portable, may want to ground to a ground rod and bond neutral. Portable generator tends to be floating neutral. Actually, you want an all-pole GFIC.)

Generator chassis is earth grounded. As is my entire solar system, even battery negative.

 

[electricthot]

Quote: Or make a cord for input of inverter to be plugged into generator. Do the N/G bond in the cord.

That's my answer...thank you.

 

[John Frum]

Generator chassis is earth grounded. As is my entire solar system, even battery negative.

More than one connection to the dirt can be a problem.

Grounding Made simpler - Part 1: AC/houshold grounding

To get the paper, click on the orange button at the top of the screen. The subject of grounding is a complex, multifaceted subject, that is often treated as an after-thought but needs to be considered from the beginning of the design and build...

diysolarforum.com

 

[electricthot]

More than one connection to the dirt can be a problem.

Three earth grounds (I live in the desert) are connected at ground level with 8 ga wire. One rod grounds mobile home to earth. One grounds electrical room (RV trailer) to earth. The third grounds solar array frame to earth. Battery negative connects to the center ground rod. Being directly connected at ground level should prevent any ground looping, shouldn't it? I should mention that my generator/inverter is now earth grounded. But I must be sure before I connect the generator to my Xantrex inverter.

 

[John Frum]

Three earth grounds (I live in the desert) are connected at ground level with 8 ga wire. One rod grounds mobile home to earth. One grounds electrical room (RV trailer) to earth. The third grounds solar array frame to earth. Battery negative connects to the center ground rod. Being directly connected at ground level should prevent any ground looping, shouldn't it? I should mention that my generator/inverter is now earth grounded. But I must be sure before I connect the generator to my Xantrex inverter.

The battery should be grounded on the downstream of the shunt and/or bms.
Please read the doco I linked.
Grounding is complicated and I'm reluctuant to get into the details.

 

[electricthot]

The battery should be grounded on the downstream of the shunt and/or bms.
Please read the doco I linked.
Grounding is complicated and I'm reluctuant to get into the details.

Sure. I'm reading it. Reading is cheaper than new equipment. Thank you.

 

[realpinochet]

Not solar related for me on this topic ..but subject is sorta the same regarding generators. I'm getting ready to wire in, using lockout kit, my portable gen to my main panel and only panel. Since my main is the only panel it's N/G bonded. My generator is N/G bonded from the factory. Per NEC code I can only have one bond so I have to pull the flipping panel off my gen and remove the N wire from the backside of the grounding lug and then either install a switch of some kind to switch between modes, use a grounding plug or just wire it into the cord like Hedges suggest for portable use. I'm not really sure why they still sell floating neutral generators any more ..I thought I read it was code for them to be bonded today. It's debatable on having two points of bond in this usage scenario. Some people don't care if they have a bond at the panel and the generator , as long as the source feed is not on a gfi circuit as that will trip the outlet since it will see some current being returned on the ground on the supply cable. My gen and a lot of others don't use gfi for the 240V side so it's not a issue. This current on the ground is only on the wire from the gen to the panel and not the house itself so some don't worry about it since it's considered low risk. I would bet a lot of emergency setups are like this..people install a lockout kit and plug in a portable generator to their main panel and don't even know about the bonding issues; even some electricians don't seem to sweat it. While it's low risk it's not code compliant. However..I'll probably unbound my gen and then when I plug it into my main panel it will pick up the N/G bond there anyways and per code only have one point of bound so no current on the ground is seen. I'd rather be compliant for legal reasons. Here's some links if ones interested as to what I found.

https://www.doityourself.com/forum/electrical-ac-dc/510124-predator-standby-genertor-bonded-neutral.html

 

[Hedges]

This current on the ground is only on the wire from the gen to the panel and not the house itself so some don't worry about it since it's considered low risk.

I feel the same way. If the only loads connected are in the house, their ground is wired to house's ground rod. If a neutral opens in house wiring, it does not result in any current through the ground wire they are using. No "objectionable current" in wires that matter to user.

If either neutral or ground opened in generator cord, the other would carry current, but that doesn't affect loads in house. An undersized wire could be overloaded, but ground wire in a 30A cord would be same gauge as the others. If both neutral and ground opened, then imbalance between L1 and L2 would make generator frame electrically live; that's the one issue I can think of.

 

[realpinochet]

I feel the same way. If the only loads connected are in the house, their ground is wired to house's ground rod. If a neutral opens in house wiring, it does not result in any current through the ground wire they are using. No "objectionable current" in wires that matter to user.

If either neutral or ground opened in generator cord, the other would carry current, but that doesn't affect loads in house. An undersized wire could be overloaded, but ground wire in a 30A cord would be same gauge as the others. If both neutral and ground opened, then imbalance between L1 and L2 would make generator frame electrically live; that's the one issue I can think of.

In that last link the user "Furd" suggest leaving the generator N/G bonded and just don't connect the ground wire from the generator to the panel and thus current can't flow back on it and be forced to use the Neutral. Thoughts? This should work in theory as if there's a dead short in the house the breaker would pop in the panel and if there's a dead short in the generator the integrated breaker should pop since it's still bonded. I was thinking of putting a switch of some sort on mine after removing the N/G ground so I can switch between bonded and unbounded easily but not sure of what kind of switch this might be. It would need to be something like a small toggle switch. This would allow me to connect to the house or to a RV etc using the correct NEC supported way.