400A parallel inverters - EG4 vs Sol-Ark

[LotsOPower]

Planning out a system for my house that has 400A service. There is a meter/main panel outside with a 320A meter and 400A main breaker, which uses parallel conductors to feed an Eaton IFS in the basement. Those parallel conductors land in a 400A breaker, which then feeds four 200A and one 400A sub-panel, each with their own 200A/400A breaker...

The short version is that I can't bring myself to completely rewire the IFS, so I had been planning to parallel two Sol-Ark 15K inverters, where each has the 200A pass-through, and some amount of PV+batteries that isn't super important to this thread. With the recent Sol-Ark/Deye fun, I started looking at EG4, but ran into a few questions after EG4 published an "EG4 400 Amp Residential Service System Wiring Diagrams" guide in December, but all 3 diagrams say: "This wiring diagram applies to a “400 Amp residential” service (400 Amp nominal Residential Service Entrances are really rated to 320 Amps split into 2 200 Amp Services. It does not apply to a True 400 Amp service with a single 400 Amp Main Breaker."

1. Does this actually require the meter/main to have two separate 200A breakers instead of parallel conductors coming off a 400A breaker?
   1. Does the Sol-Ark require the same and I just hadn't seen it?
   2. ... I suppose this makes sense given the Churod 200A relays used in the pass-through (55A make/break spec???) need limited to 200A, and under normal conditions that would be the case, but if one of the parallel inverters dies and the relay stays open, the other parallel conductor feeding inverter#2 with a closed relay could see the full load, but I'd expect inverters that are parallel capable to communicate with each-other and prevent this scenario.
2. EG4 diagrams with GridBOSS do not show the parallel 200A circuits recombining to a 400A panel
   1. Appears to be supported in the 18kPV with NO GridBOSS (diagram #3) ... well, kind of (via 70A back fed breakers)
   2. Sol-Ark shows this in their 15k parallel diagrams, and I've seen it in several YouTube install videos as well)...

As a side note, even with both cars charging, the pool running, dual ovens going, and all AC going, the house maxes out around 170A used - so all of the above is theoretical at best and really just comes down to me trying to not wait 8 months for Eaton to sell me new IFS parts or recertify the setup.

 

[SunDave]

Welcome to the forum. Did you consider backing up a single 200amp panel (or even two), and move a few loads around? There is a limit to what batteries and inverters will support unless you have an unlimited budget for the project. Depending on your setup you can even run loads in the other panels from solar until the grid goes down, then the inverter would revert to the load terminals only.

Keep in mind you could put the inverter right before your panel. It doesn't have to be right after the meter necessarily. Everyone's setup is different, but definitely spend some time considering scenarios. I ended up backing up everything on one 200amp panel with one Sol-Ark 15k, but I left another 150amp panel not backed up. I can live with one out of two panels during a power outage.

Either of the inverters you mentioned would be grid connected, and would likely require a grid tie agreement even if not selling back to the utility. They will back-feed small amounts of power to the utility even if set to zero it out. I have seen it in the charts personally.

There are instances of others paralleling inverters to utilize a 400 amp pass-through, but like you found, there will be considerable research into the breakers and wiring required. Personally I would consult an electrician for that part of it once the rest of your system is planned out.

Lots of research into UL listings, Inverter/battery UL combo listings, grid interconnect rules, and much more ahead. Take it a step at a time, and keep good notes. Good luck with your project. I hope others chime in as well.

 

[LotsOPower]

I have considered backing up just a single panel, but it would also require a full rework of the IFS (which is 18-24 months in Eaton's current backlog), and thus I've just been holding out until I could get 400A - parallel inverters is fine.

I will be grid tied, with battery backup. Not concerned about grid tie approval or back fed.

I wired the entire house and IFS, but to keep the IFS compliant, major changes need to go back through Eaton engineering.

Appreciate the thoughts!

 

[James Showalter]

https://eg4electronics.com/wp-content/uploads/2024/12/Dual-GridBOSSes-on-400-A-Residential-Service.pdf

 

[LotsOPower]

https://eg4electronics.com/wp-content/uploads/2024/12/Dual-GridBOSSes-on-400-A-Residential-Service.pdf

Thanks James! Always cool to get support straight from the source! The PDF you posted appears to be the same PDF I linked in my post, and all of the diagrams have separate 200A main breakers feeding separate GridBOSS/FlexBoss units which feed separate load panels.

Is there a wiring diagram for a single 400A main (rather than two 200A mains) and a single 400A load-panel? Something similar to the page 68/69 "2 parallel inverters" of the Sol-Ark 15K manual? They seem to use parallel conductors/terminal blocks/AC combiners to split and then rejoin the AC.

 

[Tommytwotone]

Thanks James! Always cool to get support straight from the source! The PDF you posted appears to be the same PDF I linked in my post, and all of the diagrams have separate 200A main breakers feeding separate GridBOSS/FlexBoss units which feed separate load panels.

Is there a wiring diagram for a single 400A main (rather than two 200A mains) and a single 400A load-panel? Something similar to the page 68/69 "2 parallel inverters" of the Sol-Ark 15K manual? They seem to use parallel conductors/terminal blocks/AC combiners to split and then rejoin the AC.

I have the residential 320 amp service you mention above. For me the install was not as complex as it has two 200 amp panels fed directly off the meter and, by choice and so as to simplify the install, we put one GB and two FB on what we would call panel 1 (one of the 200 amp feeds). See drawing.

With backup loads in Panel 1 the system can then push back to grid which thereby feeds the other panel PRIOR to crossing the meter.

Your install is different in that you recombine the two lines into one 400 amp service again with the Eaton IFS and that may change some things but conceptually it may not be much different. I cannot speak to how this would interact with Eaton IFS system from an NEC perspective.

If you are planning on installing just one GB, even with multiple inverters I wonder if the way we did it might work by putting a GB on one of the 200 amp services you deem to be your most important backup and then letting the sell to grid side sell to your other panels (or the grid if loads are not sufficient to use it all).

I could just be restating here and if so my apologies. Hope it helps.