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

I am using a 2P1/2P2 setup. AC In from main panel to EG4s (40A breakers) and a full separate load panel for house. For ease let's call them on grid and off grid panels.

I did not remove the EG4 bonding screws. My off grid panel does not have bonded N-G. The ground on my off grid panel is tied to the on grid ground.

Basically the off grid panel is treated as a sub-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!!
That's how it's supposed to work. But not all of these type units do it correctly. Which is why we always need to test it.
If dynamic bonding is done correctly by the manufacturer. Then there's no issues.
If not, it must be addressed by the installer.
 
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.
That's how it should be. But a lot of them aren't that way.
 
I am using a 2P1/2P2 setup. AC In from main panel to EG4s (40A breakers) and a full separate load panel for house. For ease let's call them on grid and off grid panels.

I did not remove the EG4 bonding screws. My off grid panel does not have bonded N-G. The ground on my off grid panel is tied to the on grid ground.

Basically the off grid panel is treated as a sub-panel.
That's how it should be wired if the AIO's do dynamic bonding. As far as I know, no one has reported that the EG4's do.
This is why you need to test them.
To avoid neutral current on the grounding conductor.
Because of parallel paths, caused by more than one N/G bond.
 
Thanks all! I powered four units on to start testing the NG bonding modes and heard a loud pop and everything shutdown instantly. L1-2 (second inverter on L1) had an internal failure. I am suspicious of the internal NG bond as the reason. Anyone have any thoughts?
 
I am using a 2P1/2P2 setup. AC In from main panel to EG4s (40A breakers) and a full separate load panel for house. For ease let's call them on grid and off grid panels.

I did not remove the EG4 bonding screws. My off grid panel does not have bonded N-G. The ground on my off grid panel is tied to the on grid ground.

Basically the off grid panel is treated as a sub-panel.
Thanks @PreppenWolf. This is very helpful. Best -Jay
 
I'm not sure what occurred would be N-G related right off the batt.

We're you running loads? Battery and solar on? AC bypass on?
 
@PreppenWolf - I had a small load running, just batteries (6) on. I have noticed that when I turn my units on, my 2P1, 2P2 settings are not all staying in memory, I did double check my RS232/VGA connections, which is not clear what information that is exchanging. Also not clear what the load balancing lines are for, to left of RS232 ports and when are used. Not sure if that would cause a failure. When setting up and testing, not clear what the best sequence is, I had the AC output breakers set to on. My first L2 inverter comes on for thirty seconds and powers back down. Really frustrated with Signature Solar tech support and the manual really leaves a lot missing.

Appreciate your feedback.
 
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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.
Thanks John @John Frum - after my multi split phase inverter failure, trying to understand what likely backfed the system to cause the failure or was their a phasing issue?
 
The following would be my first checks.

1) Ensure the 3 units for 2P1 are set to 2P1 and the wiring to the panel is correct (i.e. you haven't crossed a leg at the load panel)

2) Ensure the 3 units for 2P2 are set to 2P2 AND 180degrees. Also check the wiring to load panel that all three are connected to the same load panel busbar.

3) For your AC input connection, I would ensure all 2P1 units are on the same busbar in your grid main panel and 2P2 are all fed by the other leg. I don't think (I might be wrong) that you can pass through from any leg in the grid panel to any leg in the Load panel. I would assume they need to be in phase?

I am only running (2) units so I have not considered the impact of #3 for my setup.
 
Following up with everyone. The EG4’s when powered off show continuity between L and N (meaning the NG is bonded) on both input and output sides. The cause of failure is pointing to not having a current sharing wire installed in a parallel installation (more than one inverter) on a given phase. Note that the manual does have instructions or warnings on this requirement. It only states not to connect two phase differences.
 
Following up with everyone. The EG4’s when powered off show continuity between L and N (meaning the NG is bonded) on both input and output sides. The cause of failure is pointing to not having a current sharing wire installed in a parallel installation (more than one inverter) on a given phase. Note that the manual does have instructions or warnings on this requirement. It only states not to connect two phase differences.
I was about to fire up my 4 EG4 (26kW split phase) system today after finally finishing a new main panel install. Pretty complex configuration with three AC panels, ground neutral bond at main only. I hesitated due to the exact same questions you posed and the lack of any details in the manual related to inverter bonding. What did you end up doing?
 
I am running mine today (2 units 2P1/2P2), both with NG bond screw in, load panel not bonded. Main panel bonded.

I have zero current flowing on my ground wire from the load panel to the main panel. Also zero from AC In ground wire.

I've run a 1.5hp compressor, a 2hp mill, well pump and a bunch of daily driver stuff. No issues thus far. My current plan is to leave the two bond screws in at this point.
 
I am running mine today (2 units 2P1/2P2), both with NG bond screw in, load panel not bonded. Main panel bonded.

I have zero current flowing on my ground wire from the load panel to the main panel. Also zero from AC In ground wire.

I've run a 1.5hp compressor, a 2hp mill, well pump and a bunch of daily driver stuff. No issues thus far. My current plan is to leave the two bond screws in at this point.
It's only an issue when in bypass mode. (Grid powering the loads, through the inverter)
And only if the inverter bonds N/G in bypass mode.
 
It's only an issue when in bypass mode. (Grid powering the loads, through the inverter)
And only if the inverter bonds N/G in bypass mode.
Thanks @PreppenWolf and @timselectric. Unfortunately, with my 26kW inverters, 14.1kW PV, and 30kWh of battery backup, I will be in bypass mode often. Would a simple continuity test at the inverter when in bypass mode be sufficient or should I be measuring for current on ground when in bypass?
 
I was about to fire up my 4 EG4 (26kW split phase) system today after finally finishing a new main panel install. Pretty complex configuration with three AC panels, ground neutral bond at main only. I hesitated due to the exact same questions you posed and the lack of any details in the manual related to inverter bonding. What did you end up doing?
Hey @Mudd216! Congratulations on getting this far. I bet you thought it would go much faster? I have yet to get an answer from SS, been waiting over 2 weeks. I assume they have no engineering department and are merely rebranding Chinese designed items and they don’t know how to answer. That said, I am still working through this. I plan to have an answer before this Thursday.

Couple of details added below for consideration I learned on commissioning, hope this helps.


1. Ensure your current sharing cables are installed on parallels units, those that feed L1 or L2. They must be hooked up correctly or your unit(s) will die a fast death. Note the manual text “inverter 1 port A to Inverter 2 port A is referring to the current sharing cables, not the RS-232 cables.
2. Install RS-232/VGA cables and Ethernet between batteries and to your master inverter per the manual.
3. With AC power In and Out turned off, apply at least 2, more is better, batteries (10 kWh) and turn on one breaker at a time to the first inverter. Configure setting 28 for 2P1 and setting 05 for EG4 (assuming you have matched batteries) and set priority mode (03?) to SBU (solar, battery, utility). Power cycle your inverter and ensure unit is reading the battery voltage. If not, set 05 to USE and back to EG4. It took mine several tries, if stubborn power on split phase pair and try again.
4. Turn on 1-2 more batteries and Power on second phase unit (breaker and power on) (inverter 3) and in setting 28, set to 2P2 180, set 05 to USE and 03 to SBU. Check voltage on battery is reading.
5. Turn on PV inputs to both unit, observe that the battery SOC light is charging.
6. Turn on 2nd parallel unit (breaker and inverter on button) and set 28 to 2P1 and 05 to USE and 03 to SBU. Check that battery shows SOC.
7. Turn on 2nd parallel unit and set 28 to 2P2 180 and 05 to USE and 03 to SBU. Ensure battery shows SOC. Turn on remaining PV and check that batteries show SOC charging.
8. Close PV switches and push the power off on any inverter, they should all go into standby mode (horizontal panel light goes out) and units power off within 30-45 seconds. Turn off
9. Power on each unit staring with master and check to ensure phase settings remained, ensure 2P2 units read 180 and not 120. Check that batteries are showing SOC. Power off all PV inputs and power down units.
10. Ensure all batteries are at the same voltages, using stand alone charger or using inverters powering one unit on at a time until SOC is 100%. This may take several days as mine took about 4 hours for each battery.
11. Power off large house loads, A/C, heater, oven and turn off main house power. Energize system starting with batteries, then PV ensure system is stable and turn on AC input breakers and the AC output breakers.
 
Hey @Mudd216! Congratulations on getting this far. I bet you thought it would go much faster? I have yet to get an answer from SS, been waiting over 2 weeks. I assume they have no engineering department and are merely rebranding Chinese designed items and they don’t know how to answer. That said, I am still working through this. I plan to have an answer before this Thursday.

Couple of details added below for consideration I learned on commissioning, hope this helps.


1. Ensure your current sharing cables are installed on parallels units, those that feed L1 or L2. They must be hooked up correctly or your unit(s) will die a fast death. Note the manual text “inverter 1 port A to Inverter 2 port A is referring to the current sharing cables, not the RS-232 cables.
2. Install RS-232/VGA cables and Ethernet between batteries and to your master inverter per the manual.
3. With AC power In and Out turned off, apply at least 2, more is better, batteries (10 kWh) and turn on one breaker at a time to the first inverter. Configure setting 28 for 2P1 and setting 05 for EG4 (assuming you have matched batteries) and set priority mode (03?) to SBU (solar, battery, utility). Power cycle your inverter and ensure unit is reading the battery voltage. If not, set 05 to USE and back to EG4. It took mine several tries, if stubborn power on split phase pair and try again.
4. Turn on 1-2 more batteries and Power on second phase unit (breaker and power on) (inverter 3) and in setting 28, set to 2P2 180, set 05 to USE and 03 to SBU. Check voltage on battery is reading.
5. Turn on PV inputs to both unit, observe that the battery SOC light is charging.
6. Turn on 2nd parallel unit (breaker and inverter on button) and set 28 to 2P1 and 05 to USE and 03 to SBU. Check that battery shows SOC.
7. Turn on 2nd parallel unit and set 28 to 2P2 180 and 05 to USE and 03 to SBU. Ensure battery shows SOC. Turn on remaining PV and check that batteries show SOC charging.
8. Close PV switches and push the power off on any inverter, they should all go into standby mode (horizontal panel light goes out) and units power off within 30-45 seconds. Turn off
9. Power on each unit staring with master and check to ensure phase settings remained, ensure 2P2 units read 180 and not 120. Check that batteries are showing SOC. Power off all PV inputs and power down units.
10. Ensure all batteries are at the same voltages, using stand alone charger or using inverters powering one unit on at a time until SOC is 100%. This may take several days as mine took about 4 hours for each battery.
11. Power off large house loads, A/C, heater, oven and turn off main house power. Energize system starting with batteries, then PV ensure system is stable and turn on AC input breakers and the AC output breakers.
Thanks, that's a nice write-up. I stumbled through a slightly different procedure. I struggled getting my 2p1/2p2 configured. It kept timing out which made it more difficult for me to identify my error (I wasn't actually saving the 2p2 change). It also took me a bit to figure out I needed 3 inverters set to USE. I am hoping to test powering the whole house on battery and bypass mode today (gonna take a while to get the panels installed) assuming I get enough confidence with the inverter bonding.
 
Thanks @PreppenWolf and @timselectric. Unfortunately, with my 26kW inverters, 14.1kW PV, and 30kWh of battery backup, I will be in bypass mode often. Would a simple continuity test at the inverter when in bypass mode be sufficient or should I be measuring for current on ground when in bypass?

I'll check out bypass mode when our grid power comes back on. Gonna be at least another day.
 
Thanks @PreppenWolf and @timselectric. Unfortunately, with my 26kW inverters, 14.1kW PV, and 30kWh of battery backup, I will be in bypass mode often. Would a simple continuity test at the inverter when in bypass mode be sufficient or should I be measuring for current on ground when in bypass?
Need to test for Continuity between neutral and ground, in bypass mode. But without an incoming ground. (Otherwise you will read the main service panel N/G bond)
 
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