Common Neutral Split Phase and Neutral-Ground-Bond EG4 Six Inverter Installation

[JCSchwarb]

All-

I have read a lot of confusion on how the EG4’s switch the neutral depending on AC pass through, battery charging, etc. Note that my only Neutral-Earth-Ground bond occurs in my first means of disconnect from the power line meter. So appreciate final thoughts on the Neutral-Earth-Ground NEG bond and the ground loop issues many have weighed in on, but without complete resolution in my observations. Specifically, why do some inverters have internal NEG bond and why aren’t their instructions on how to properly configure units for safety?

Appreciate your help soonest so I can commission my system and sleep better at night. Appreciate any explanations or pointers on how the system works if the EG4’s will cause anomalies or issues in my installation setup.

Thank you!
-J

 

[sunshine_eggo]

I don't know anything about how the EG4 handles N-G bonds. would assume N-G bond when inverting and broken when passing through AC/charging, but no idea how they handle it in parallel operation.

IMHO on such a complex setup, I would make the N-G bond at the AC panel and break it at all of the inverters all the time.

On my Victrons, it's simple. I can manually control the N-G bond. The single inverter providing L1 has the N-G bond enables, the L2 inverter N-G bond relay is open.

 

[JCSchwarb]

Thank you for your reply and recommendation. I have read about one phase like L1 having a NG bond while leaving L2 open. It is not clear to my why any inverters need to have a NG bond.

 

[timselectric]

The best option (which requires opening the inverters) is to disable inverter N/G bonding (if it actually exists). And carry the common neutral, from the first means of disconnect, through your system, to the final loads panel.

 

[NEpowerandlight]

 

[JCSchwarb]

Tim - thank you so much. This seems to make the most sense. Any insights on common neutral question is much appreciated! -J

 

[JCSchwarb]

Thank you! Will’s explanation is excellent, but only applies to an off-grid setup with the main panel with NG bond at the inverter(s) AC output. Unfortunately, Will’s video is one of many configurations so folks need to be careful applying this to everything.

To further explain:
In Will’s video, he has an off-grid configuration supplying a “main” panel on the inverters AC output side. This panel has the NG bond and therefore any power input should not be bonded at the inverter and main panel, so Will is correct on removing the inverter(s) NG bond to be “NEC” compliant with one NG bond.

I am concerned that the manufacturer doesn’t cover this important safety configuration regarding different NG bonding configurations, but rather says making a change to the inverter will void the warranty. Going inside the inverter takes skill and confidence as some disassembly is required to get to the screw Will mentions removing. I would not recommend doing this as faults could be induced via connector damage or other issues. I think that Signature Solar’s EG4 Inverters need a way to control this internal NG bond via software or purchasing the item preconfigured for the installation of choice. A manual update or supplement drawing needs to be supplied to explain how to ensure NEC compliance and safety.

Regarding Will’s comment on bypass mode in the video, this implies grid tied with an AC input and is a completely different configuration so not sure why that was thrown in so quickly without unpacking it for the audience. I am confident with Tim’s explanation that the NG bond at first means of disconnect gets pulled through the inverter AC input (i.e., when grid tied) to the output supply panel.

 

[timselectric]

Thank you! Will’s explanation is excellent. I am concerned that the manufacturer doesn’t cover this important safety configuration, but rather says making a change will void the warranty.

Not sure what bypass mode is that Will mentions. I will need to understand this, but am confident with Tim’s explanation that the NG bond at first means of disconnect gets pulled through the inverter to the output supply panel.

Bypass mode is when the inverter passes grid power through to the loads. Bypassing the inverter and batteries.

 

[JCSchwarb]

Thanks!

 

[sunshine_eggo]

Thank you! Will’s explanation is excellent. I am concerned that the manufacturer doesn’t cover this important safety configuration, but rather says making a change will void the warranty.

Code compliance is the responsibility of the installer. Manufacturers and manuals do not address code compliance. Codes change, and they may dig themselves a hole.

 

[sunshine_eggo]

The best option (which requires opening the inverters) is to disable inverter N/G bonding (if it actually exists). And carry the common neutral, from the first means of disconnect, through your system, to the final loads panel.

Please confirm we said the same thing in different ways. Break the bond in all and bond at the panel.

 

[timselectric]

Please confirm we said the same thing in different ways. Break the bond in all and bond at the panel.

Main panel, yes. Loads panel, no. (If connected to grid)

 

[JCSchwarb]

Code compliance is the responsibility of the installer. Manufacturers and manuals do not address code compliance. Codes change, and they may dig themselves a hole.

 

[JCSchwarb]

Thank you, but your comment adds little value to my question. There is nothing in the manual that provides instructions on how to configure neutral-earth-ground bond in various configurations. I am still scratching my head why the EG4 or other similar inverters have an NEG bond on battery power. This is the point I am trying to understand.

 

[JCSchwarb]

Main panel, yes. Loads panel, no. (If connected to grid)

Thank you. Understand. My only concern is inside the inverters themselves since a diagram or instructions are not provided with the product. Most electricians that I know would not go to this level of detail. Having to open the internals to a box does not feel right, but clearly is necessary. Thanks again!

 

[JCSchwarb]

I did some testing this morning and discovered that the EG4 6500 bonds neutral to ground when the unit is off. There is no good reason for this, unless the unit is stand alone and not connected to a distribution panel for a whole house system. Scratching my head on what to do. I can’t unbond the inverter, so what are my options other than sending it back?

 

[timselectric]

Looking at your first post picture.
It appears that the inverters are mounted on non conductive surfaces.
If you can verify that the inverters N/G bond is active at all times. (In all modes and when completely shut down) I have an unconventional solution.
Not for public consumption. lol

 

[JCSchwarb]

The walls are non-conductive, durarock. I would have to test other modes to determine when the bond is open, if ever. I think I know where you are going…

 

[JCSchwarb]

The best option (which requires opening the inverters) is to disable inverter N/G bonding (if it actually exists). And carry the common neutral, from the first means of disconnect, through your system, to the final loads panel.

Tim - I went back and looked at removing the inverter NG bonding screw and it turned out to not be viable. The design requires internal CCA disassembly (Will is much more brave than me ). Since Signature Solar (EG4 support) is slow to provide me with drawings and information, I will be testing with AC input applied as pass through to determine if the NG bond is open and then test if bond is closed in Battery or Solar.If my assumption proves correct through testing, then the inverters will be able to support my installation since my main NG bond will be isolated on the supply side panel and will not conflict with the load panel when the inverter is in battery or solar (DC) mode since the neutral and ground from the supply panel will be disconnected.

Please confirm if you agree/disagree. Thank you!!

 

[John Frum]

I did some testing this morning and discovered that the EG4 6500 bonds neutral to ground when the unit is off. There is no good reason for this, unless the unit is stand alone and not connected to a distribution panel for a whole house system.

Coming in late, hopefully I'm up to speed...
Pretty sure most AIO's and inverter/chargers have N bonded to G when the ac input to the unit is not energized.
Its the non energized position for the relay.