Swapping an old Fronius string inverter for a Sol-Ark - need a sanity check

I've got a system installed around 2011 on my roof that has 36 250w panels in a 12s3p configuration. PVWatts says the most I get (and I can confirm) is around 7200w a/c out of the setup since it's kind of west-facing.
It currently runs to a Fronius 10.0 ig plus inverter that everyone claims is well beyond its expected lifespan (though it seems to run fine).
This simple setup with 2011-era code compliance backfeeds a 60a breaker on the main meter/main combo panel.


My thinking is as follows:
1) Swap the current Fronius with a Sol-Ark 15K. The existing string is at the limits of what Sol-Ark is happy taking in on MPPT-1 (right at 500 voc at 0 degrees, but the max my Fronius has seen is 502v in its entire 11 years of life), and it will clip to 6500w.
2) Replace the 60a backfeed breaker with a 70a feeder to the GRID input of the sol-ark
3) Run the LOAD output of the sol-ark to a "critical loads" panel.
4) Ground-mount a Fortress e-flex outdoor things near the Sol-Ark and wire it up to the batteries
5) Optionally ac couple another 5kw of microinverters to another building on my property - with a dedicated circuit run all the way back to the sol-ark

At this point, I've got critical loads backup, slightly less PV production than before, and a new inverter.

Concerns:
1) I'm not modifying the existing roof array and adding RSD (required for new installs) since it wasn't installed that way and I assume it's not irresponsible to leave it untouched. Is this hack?
2) I need to limit my grid sell-back to around 10kw per my interconnect agreement (NEM 1) - I assume that the Sol-Ark will power loads, then charge the battery, then send the remainder to the grid (in that priority order) but does it attenuate dc or ac production if the loads and battery consumption are not enough to absorb all the pv production? I would assume it attenuates the dc first since while grid-tied, I think the ac coupling is all-or-nothing (I may be wrong on this).
3) Is there a more popular outdoor rated battery enclosure solution? There isn't a good option for bringing them indoors. I have some space for a shed of some sort, but it seems like more hassle (building/buying a shed, insulating it, thermally controlling it) than just buying a solution designed for outdoor exposure. I realize the temperature variation will probably be harder on the batteries but...
4) I read somewhere that the actual max voltage input for the sol-ark mppt is 550v which I doubt i'll ever see, but due to me not wanting to reconfigure my current array at all (leave well enough alone) - am I ok?

Appreciate the help in advance. I've been doing a ton of reading but don't want to head down some invalid path with my assumptions.

Also - anyone in the bay area work through one of those third party permitting/design companies?

If your pulling a permit, anything the work touches is required to be updated to the current in use codes.

Since the inverter is still working I would just leave it as is. When the the inverter fails, I would just swap out of a straight grid-tie unit ( no permits required )

If you go the permit route, your in CA, which means your looking at losing your current net metering agreement, which will severely change the economics of even having grid tie solar.

Solar Guppy said:

If your pulling a permit, anything the work touches is required to be updated to the current in use codes.

Since the inverter is still working I would just leave it as is. When the the inverter fails, I would just swap out of a straight grid-tie unit ( no permits required )

If you go the permit route, your in CA, which means your looking at losing your current net metering agreement, which will severely change the economics of even having grid tie solar.

Click to expand...

But permitting doesn't require me to notify the utility company, so I imagine NEM 1.0 stays in effect. I just figure it might be worth trying to have valid permits for the electrical work in the unlikely event I ever had an insurance claim etc

Max voc is 500v. Is the 502v when producing (that is not voc)? How did you measure 502 voc?

I would take 2 or 3 panels from each string and make a 4th string. 3 would be ideal so all are the same length and can be combined.

Sol-ark has a grid limit for exporting you can set.

nuke said:

But permitting doesn't require me to notify the utility company, so I imagine NEM 1.0 stays in effect. I just figure it might be worth trying to have valid permits for the electrical work in the unlikely event I ever had an insurance claim etc

Click to expand...

The meter will have to be pulled for the Sol-Ark ( 15K ) installation as it becomes the main with the built in 200A breaker, that will require the power company to be notified.

Additionally, your signed agreement with the Electric company is you are required to provide notice to any changes in the system.

This isn't "an imagine" thing you just make up as you go along, CA power providers are highly incentivized to move you to NEM 3.0, your proposed changes give them the that right.

Solar Guppy said:

The meter will have to be pulled for the Sol-Ark ( 15K ) installation as it becomes the main with the built in 200A breaker, that will require the power company to be notified.

Additionally, your signed agreement with the Electric company is you are required to provide notice to any changes in the system.

This isn't "an imagine" thing you just make up as you go along, CA power providers are highly incentivized to move you to NEM 3.0, your proposed changes give them the that right.

Click to expand...

But I am doing a partial backup using a backfeed breaker

DIYrich said:

Max voc is 500v. Is the 502v when producing (that is not voc)? How did you measure 502 voc?

I would take 2 or 3 panels from each string and make a 4th string. 3 would be ideal so all are the same length and can be combined.

Sol-ark has a grid limit for exporting you can set.

Click to expand...

Voc needs to consider temperature. STC voc is like 460.

You can AC couple the old inverter into the Solark and attach your loads to the Solark.
Or you can swap in the Solark and connect the PV and loads to it. The PV input is tolerant of too high voltage input but will throw an alarm.
What your utility company make of it if you go this route if they find out ????

Quattrohead said:

You can AC couple the old inverter into the Solark and attach your loads to the Solark.
Or you can swap in the Solark and connect the PV and loads to it. The PV input is tolerant of too high voltage input but will throw an alarm.
What your utility company make of it if you go this route if they find out ????

Click to expand...

I think officially you can modify the system up to 1kw over the original size without requiring a new interconnect agreement

nuke said:

I think officially you can modify the system up to 1kw over the original size without requiring a new interconnect agreement

Click to expand...

Adding of storage will REQUIRE you have your interconnection agreement updated in CA, no NEM 1.0, it will be NEM 3.0

Solar Guppy said:

Adding of storage will REQUIRE you have your interconnection agreement updated in CA, no NEM 1.0, it will be NEM 3.0

Click to expand...

That certainly sucks. I wonder if they'll let me swap in a hybrid inverter solely in a grid-tie configuration though.

If you install anything behind your original inverter they are not going to know a damn thing.

Solar Guppy said:

Adding of storage will REQUIRE you have your interconnection agreement updated in CA, no NEM 1.0, it will be NEM 3.0

Click to expand...

Actually I now dont think this is true. The internet is littered with stuff to the contrary.

Maybe the best thing to do is just see if I can get a hybrid inverter and batteries permitted. At that point the only questionable thing is the amount of PV but that's a separate problem I guess. Any other thoughts?