I reread your question.
I think the only way to be sure the internal transfer switches in the inverters all switch at the same time on a big high load ( exceeding potentially the max current rating of a single relay) multi stack inverter system is to use external transfer switch’s.
The system I installed is never going to exceed 200 amps, probably never exceed 80 amps. 2 inverters can more than handle the load. The 3rd was installed as built in redundancy to make it easier in case one fails. As the system won’t run on 1. So I didn’t have to worry about exceeding relay capacity.
I think this is one of the potential problems with paralleled systems vs larger single 120/240 inverter’s which we don’t really have here in the US.
I have a 3 stack eg4 18k and while watching the inverters online they are totally balanced.
Jay On Feb 4, 2026, at 4:29 PM, Jason Szumlanski via RE-wrenches <[email protected]> wrote:
Hi all,
When backing up a 400A service with multiple paralleled all-in-one inverters by combining the AC inputs and outputs, the individual inverter transfer switches must operate in a synchronized manner. Come to think of it, the same thing applies to backing up 200A service with paralleled inverters. Are these tested for this function? – I assume so.
I'm really asking because Sol-Ark seems to be the only brand that specifically addresses 400A service in documentation, although not very clearly in the manual itself. Their training and literature support passing through additive grid pass-through with multiple inverters, which implies that they are additive in their ability to transfer power. See attached examples.
I have not found anything from EG4 (for the 18kPV) or the Midnite AIO that specifically addresses this.
In other words, how can we assume that paralleled inverters will be additive in terms of their ability to transfer high levels of current that exceed the rating of a single unit? Is that even addressed in listings? The documentation is quite poor from all manufacturers (no surprise there!)
I do have a couple of grid-interactive Midnite AIO systems with four paralleled AIOs backing up 400A services, and so far, so good. My engineer signed off on that.
![]() <Image 1171.jpg> <Image 1172.jpg> _______________________________________________List sponsored by Redwood AlliancePay optional member dues here: http://re-wrenches.orgList Address: [email protected]Change listserver email address & settings:http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.orgThere are two list archives for searching. When one doesn't work, try the other:https://www.mail-archive.com/[email protected]/http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.orgList rules & etiquette:http://www.re-wrenches.org/etiquette.htmCheck out or update participant bios:http://www.members.re-wrenches.org
|
_______________________________________________
List sponsored by Redwood Alliance
Pay optional member dues here: http://re-wrenches.org
List Address: [email protected]
Change listserver email address & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
There are two list archives for searching. When one doesn't work, try the other:
https://www.mail-archive.com/[email protected]/
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
http://www.re-wrenches.org/etiquette.htm
Check out or update participant bios:
http://www.members.re-wrenches.org
