Ground-Neutral bonding the inverter, GFCI question

[meetyg]

Hi.
I have a 220v AC/12v DC Xijia (CNSPower) 1500w inverter.
I'm using it in a portable solar generator setup.
The inverter doesn't have ground-neutral bonding, same as most of these types of inverters (Giandel, etc...).

The output of the inverter AC socket goes to a small panel box, which houses an AC breaker with ground fault protection (GFCI) and a watt meter. Then from this box, AC out goes to a 3 pin socket. See picture:



In general, I understand that for most portable uses, using it with a floating neutral is OK.

But for the GFCI to properly protect from ground faults (and electrocution) I understand that these two conditions must be met:
1. I need a ground-neutral bond, before the GFCI.
2. I need a real ground somewhere (e.g. ground rod)

Am I correct?

If I bond the ground-neutral before the GFCI, but do not have a true ground, would this be any more dangerous than just leaving the neutral floating?

Since this is a portable build, I might not always have a true ground/earthing available. That's why I'm asking...

Another reason I want a ground-neutral bond is because I might want to charge an EV from this portable generator. Most portable EV chargers check the bonding before allowing to charge the vehicle. Of course this would be pushing it a bit for a 1500w inverter, but there are some portable chargers which can be set to 6 amps AC, which at 220v would be around 1300w.
In case I will charge an EV, then I will make sure I have a true ground.

But the question is can I leave the ground-neutral bond, even when not really needing it, and when ground might not be available?

Thanks.

 

[FilterGuy]

Am I correct?

I have not worked with GNC DIN mounted GFCI breakers, but all of this class of breakers will *at least* look for differential current between Hot and Neutral. This means that if any current is going someplace other than the intended circuit, the breaker will pop. The breaker only needs to see the current on Neutral and hot to do this, so it will work even if there is no Equipment Grounding Conductor or earth ground.

At least here in the US, if retrofitting an old system that does not have grounding wires, it is allowed to use GFCI outlets in order to provide proper protection.

If I bond the ground-neutral before the GFCI, but do not have a true ground, would this be any more dangerous than just leaving the neutral floating?

No, Adding an NG-bond without a grounding electrode does not make it more dangerous.

But the question is can I leave the ground-neutral bond, even when not really needing it, and when ground might not be available?

Yes.

HOWEVER:
My answers above are for quality inverters. Some lower-quality inverters specifically say do not create an N-G bond on the output (Giandle in particular).

 

[meetyg]

I have not worked with GNC DIN mounted GFCI breakers, but all of this class of breakers will *at least* look for differential current between Hot and Neutral. This means that if any current is going someplace other than the intended circuit, the breaker will pop. The breaker only needs to see the current on Neutral and hot to do this, so it will work even if there is no Equipment Grounding Conductor or earth ground.

At least here in the US, if retrofitting an old system that does not have grounding wires, it is allowed to use GFCI outlets in order to provide proper protection.

No, Adding an NG-bond without a grounding electrode does not make it more dangerous.

Yes.

HOWEVER:
My answers above are for quality inverters. Some lower-quality inverters specifically say do not create an N-G bond on the output (Giandle in particular).

I have seen various posts about Giandel inverters, but that just made me even more confused. If I recall correctly, Andy from Off-Grid-Garage has done this (without GFCI) on his 3000w Xijia, In order to charge his Tesla. But in his case he had it properly grounded.

My concern is that while the GFCI will detect imbalance between hit and neutral, this current has to go somewhere. If the inverter is not grounded, this means the current will be absorbed by the person...

 

[mrzed001]

Hi.
I have a 220v AC/12v DC Xijia (CNSPower) 1500w inverter.
I'm using it in a portable solar generator setup.
The inverter doesn't have ground-neutral bonding, same as most of these types of inverters (Giandel, etc...).

The output of the inverter AC socket goes to a small panel box, which houses an AC breaker with ground fault protection (GFCI) and a watt meter. Then from this box, AC out goes to a 3 pin socket. See picture:

View attachment 103646

In general, I understand that for most portable uses, using it with a floating neutral is OK.

But for the GFCI to properly protect from ground faults (and electrocution) I understand that these two conditions must be met:
1. I need a ground-neutral bond, before the GFCI.
2. I need a real ground somewhere (e.g. ground rod)

Am I correct?

If I bond the ground-neutral before the GFCI, but do not have a true ground, would this be any more dangerous than just leaving the neutral floating?

Since this is a portable build, I might not always have a true ground/earthing available. That's why I'm asking...

Another reason I want a ground-neutral bond is because I might want to charge an EV from this portable generator. Most portable EV chargers check the bonding before allowing to charge the vehicle. Of course this would be pushing it a bit for a 1500w inverter, but there are some portable chargers which can be set to 6 amps AC, which at 220v would be around 1300w.
In case I will charge an EV, then I will make sure I have a true ground.

But the question is can I leave the ground-neutral bond, even when not really needing it, and when ground might not be available?

Thanks.

There is one problem with grounding these "simple" inverters ... they are NOT ISOLATED !

One of the users in the Hungarian group made a very good demonstration video (sorry, it is in Hungarian language ... but you can see what he is doing)

He uses:
- 12V battery
- a "simple" inverter like you use (500W about 220V x 2,3A)
- a ground rod
- a second ground rod representing you standing in the ground
- an RCD in the inverter output

First inverter is not grounded (Floating ground)
- Line to ground = 0V
- Line to Neutral = 204V (not to strong 220V inverter)

Then he connects Neutral to Earth rod.
- Neutral to ground and Neutral to second ground is 0V
- RCD working, tester shuts it down

And here comes the interesting part:
- Both battery terminal to the second ground (you) = 110V
- Both battery terminal to the second ground (you) = 0,7A
THAT IS LETHAL !

At last he tries to ground one of the battery terminals (sparks), inverter shuts down with short circuit.


So if you use a simple, NON ISOLATED inverter and have to ground its output ...
always assume the battery cables and terminals have lethal AC current present !

 

[tagjags]

You can watch the video in english: to the left of the word YouTube,on the bottom, click on the 6 tooth gear; activate subtitles; then select auto translation to english (or any? language on the looooong list) ; for the 5 seconds i tried it, it seems to be a perfect translation.

 

[tagjags]

Watch at 01:40 how he grabs a 220 V AC live naked line with his bare hand,and nothing happens;

When electricity is created at the alternators, there exists no ground , the one grounded wire is created later by the electric company,the generators only produce live wires,not ground,just like our inverters with the 2 live AC wires, sinewave on both; so,in other words,they grab one of the live wires and run it into the ground,and from then on,that live wire they call Ground; and,of course,if you stand on the earth, Ground now, and grab the other wire,you die; why they do that,no one is 100% sure...

So,our hungarian friend there,thank you very much for the excellent video, he grabs the HOT 220 V AC and he feels nothing; of course not, the circuit is not closed, the other line has not been run into the ground yet; like the unharmed birds on the HV wires, the circuit is open; but the guy who pees on the electric fence for the video... he most likely won't do it again º.º

 

[Hedges]

The GFIC (or residual current breaker if you call it that) should interrupt both poles, line and neutral, to ensure you are protected no matter which you come into contact with. In the U.S. we use those for portable power cords, since can't trust outlet to be wired correctly.

In the U.S. we use 5 mA threshold for human safety. The 30 mA GFCI could be above the "can't let go" threshold without tripping, are used for equipment protection and for the funny utility connections found in other parts of the world.

A ground rod would be good to provide a grounded pin in the socket, if it takes a 3-prong plug.

 

[tagjags]

yeah, 30 years ago they were called just GFIs;
i still have laying around somewhere a relic 110v (here we use 220V) hair drier(vidall sasson??) from NYC with a GFI at the end of the cord,in the plug,a very boxy plug indeed; i used to live in NY and NJ,for 20+years.