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I know the correct behavior (for safety reasons) is to stop powering loads on AC-in-1 after grid failure, but is there a regulatory approved device similar to a generator automatic transfer switch (ATS) coupled with an assistant that would enable this?
The answer it is not possible and this is also a really bad idea.
Why can't you just feed the ATS from the AC-OUT? This would work and is how the inverter is designed to operate.
@shaneyake Why is it a bad idea? First, if I connected all my loads to the AC-out I wouldn't need an ATS. ATS's are how generators isolate from the mains to prevent back feeding. How is an inverter any different from a generator? I have a 200A/240V split-phase service. The Quattro's can't handle the feed through current. They are limited to 100A. For my application paralleling with ESS and managing the load after a grid failure would be optimal. Otherwise, I'd have to rewire to separate loads.
The reason I believe it is a bad idea is because it is important for the inverter to be in control of the transfer, this is both for safety and for setting up the transfer, like frequency shifting to match in coming feed, etc. The second is because it is against the convention, typically if you turn off the supply to an inverter that feed will be safe to work on. This is the case for all smaller inverters, doing something diffrent opens the doors for accidents.
An ATS is as you said an automatic transfer switch. This does but isolate the generator from the grid but rather transfers the load from the grid to a generator, typically with some bref outage. The generator is never connected to grid.
Yes, a single Quattro is limited to 100A but you can parallel 2 and then you will have 200A passthrough. That is one option.
An ATS is simply a 2 in - 1 out switch. You can connect your incoming grid feed to IN A and the AC-OUT of your Quattro to IN B. This would achieve exactly what you are trying to do. If the case of a grid outage all your loads would be transferred to the Quattro. You would probably want to just use a Transfer Switch so you can manual transfer once you have turned off loads so you don't overload the Quattro.
The only exception is that the Quattro needs to be connected to grid before the transfer switch or have it's input disconnected when the transfer switch is active if it is feed from the same panel that the transfer switch is feeding. As you can't connect the AC-IN to AC-OUT.
"How is an inverter any different from a generator?" Generators don't have AC-IN, only AC-OUT. If you think of a Quattro as only having an AC-OUT then you would wire it exactly like you would wire a generator.
@shaneyake Thanks for your thoughtful answer. I understand and agree with all your points. Searching around this site, this question has been asked many times in different ways. All the solutions proposed seem like clumsy workarounds to defeat anti-islanding regulations when safe islanding is a highly desirable feature. With all the intelligence in the Victron (and other) products there should be a safe way for islanding. It's hard to believe that a device like this doesn't exist. Something similar to a smart meter or voltage/frequency relay (Ziehl) that could be controlled with an inverter assistant to monitor for mains failure then open a contactor safely isolating the mains. Then have the inverter energize the AC-in to power loads on that circuit. Momentary power loss while assessing the nature of the mains failure would be acceptable. Critical loads on the AC-out would be unaffected. This assumes the inverter is sized correctly or you manage the loads on the AC-in. When the mains failure are resolved, the inverter assistant signals the device to close the contactor to resume normal operation.
I don't have the drawing abilities you have but your suggestion is suboptimal due to a geography challenge. I have three buildings (1,2,3) all served by a single 200A 240v split phase service that's on a pole with the meter and feed panel not local to any of the 3 buildings. Building 1 is 200ft from the feed panel and is served by a 100A breaker. Building 2 is 100ft from the feed panel and is served by a 200A breaker. Build 3 is 100ft from building 2 and served from a sub panel in building 2 from a 70A breaker. Building 1 will contain all the Victron equipment. (2) Quattro's (48/5000/70-100/100 120V) in a split-phase configuration, (2) 48v 304ah batteries, and a Smart Solar MPPT RS 450/100 with (16) 415W solar panels. All uninterruptible critical loads served by the AC-out reside in building 1 only. Building 2 is a shop that has several high load devices such as a 4hp air compressor, 30hp CNC machine, auto lift and other industrial machines. These devices will never be operated during a mains failure. Building 2 also has critical loads such as surveillance cameras, security system, lighting, pressure pump, electric roll up doors, etc. Building 3 only has surveillance cameras, security system, lighting, etc. Currently all 3 buildings critical loads (managed) are served happily by a single Honda EU7000is generator during a mains failure from the feed panel. I have 2 requirements. 1) Reduce electric bill with ESS by back-feeding loads from building 2 & 3 and generating power for AC-out loads in building 1. 2) During mains failure power critical loads in all 3 buildings. Your ATS configuration would work, but I'd have to mount the transfer switch at the main feed panel and trench an additional 200ft line from building 1 to it.
