@budgetsolarinstall You are correct that the Sol-Ark cannot frequency shift while connected to grid, as the Sol-Ark is locked into the grid frequency and simply following grid frequency while "on-grid". The Enphase system can be connected to the load side of the Sol-Ark, or to the gen terminals and the Sol-Ark can then be configured accordingly. This will give you the ability to still utilize the Enphase system during grid outage. However, in order to do zero export with the Enphase system, you will need to use their CTs, and install them directly before or after the Sol-Ark CTs. Shouldn't really matter which side, as long as they are both (SA and Enphase CTS) installed between your PoCo meter and the first breaker panel.
Something that I do not know, but you should double check, is whether or not the Enphase system will do frequency shift curtailment when it is configured for zero export! A
zero export configuration could override the frequency shift function, as the Enphase system then "knows" what to do purely off of the CT readings. This may end up giving you no frequency shift control in a grid down scenario!
If this is the case, you will want to be sure and have the Enphase system running off the gen terminals of the Sol-Ark! The reason being that the Sol-Ark can then open the gen terminal contactors, in order to cut off charging when the batteries are nearly full, to avoid overcharging the batteries!
Another option would be to just tie the Enphase system in directly to your "grid-only" panel, then you don't have to worry about overcharging the batteries. You also would then not get any PV power from the Enphase system when grid is down.
One note* When using 2 separate systems that have their own CT sensors, you will not get as good control over the zero export function! You tend to get periods where the 2 systems shift back and forth on power and then you get "overshoot" scenarios where you sell back for a little until the system "throttles back" production again. One thing that can be done to help this is to set the "buffer" watts different for the 2 systems. E.g. set minimum import number for Enphase to 50 watts and set Sol-Ark to 100 watts. This helps mitigate this effect, but will probably not completely solve the issue. (By the way, I do not know if Enphase has this setting for sure. I am not familiar with Enphase's settings, etc. However, I do know that Sol-Ark has this setting, and if Enphase does not have it then you can simply set the Sol-Ark to somewhere between 50-100 watts rather than zero, as the Enphase system will likely be shooting for a near zero number.)
A scenario like yours always works a lot better when you have a single system, rather than multiple systems trying to "play nicely". However I don't know your scenario, maybe you have too much solar to use only the Sol-Ark, or maybe this is a "retrofit" battery add-on to an existing Enphase system. But this is something for others to keep in mind if designing a new setup! The less mixing of brands in one setup, the smoother the setup will function, inevitably! And if someone is looking for rapid shutdown function, then I would say look at AP Smart RSDs or Tigo optimizers, if optimizers are needed, but I would recommend optimizers if not needed, as efficiency losses make them not worth using if you don't have partial shading for a decent portion of the day! Soon Sol-Ark's own optimizers will be available, then I would of course recommend using those!
