options to combine multiple inverters

[secondhandluck]

I am just finishing up some of the design details of a system using two inverters, and have a question about the best way to have them connected with a single exterior AC disconnect. The system has two separate arrays, feeding two separate Sunny Boy SB-4000us inverters. The spec sheet shows 17A each and I was told to run them on 20A breakers. I am using Tigo TS4 optimizers for rapid shutdown, and with one exterior disconnect the Tigo transmitter will shut down all of the panels. After plenty of reading, I see that I can run the two inverters to a sub panel to combine them, then run the sub panel feed to the disconnect, and exterior disconnect to the main panel. Or I could use this AC combiner box/ shutdown from MIdnite Solar, which essentially has the AC breakers for each inverter in the disconnect. Looks like a nice piece of gear, but $$ for what it is.

https://s3.amazonaws.com/ecodirect_docs/MIDNITE/MNPV6_DISCO.pdf

Or, another suggestion was to run L1 and L2 from each inverter (4 lines total) to a 4 pole exterior disconnect, and then back to the main panel. This way each inverter has it's own breaker in the main panel, and I don't combine them. The Tigo rapid shutdown transmitter would work with this .
Thoughts? What am I missing?
SD

 

[Proteus]

I have essentially the same questions. Combining the two ac lines into one creates a really expensive solution. I think I'm just going to put in two small-as-i-can-find safety cutoffs for each AC output from my two inverter strings. I looked at discos from that mfr too.

 

[secondhandluck]

I ended up running both string inverters to a 60A subpanel, , and then ran the sub panel through an exterior disconnect, and then back to the main panel backfeed breaker. All township and utility approved.