Would this be with no DC coupled PV at house, all PV at barn and AC coupled to SolArk?
Last I heard, SolArk recommended having DC coupled PV greater than AC coupled.
Yes, this was the idea. I sort of forgot SolArk recommends that after seeing success stories with 18kpv in 100% AC coupled config. In my defense it's because searching multiple times for a technical explanation for why SolArk needs that came up empty.
Alternatives would be a battery inverter at the house which fully supports AC coupling (e.g. Sunny Island)
Sure.
But the SMA battery inverters have wimpy surge. Any other brands support remote transfer (disconnect) switch that could be located at grid connection?
Enphase calls it Microgrid Interconnection Device. Couple of the Chinese companies have these, and I think EG4 teased something that could be one in the recent trade show.
You would still need to pull a control wire all the way to the barn to connect to the grid forming inverter. And this wire needs to be reasonably well protected.
All of these AC coupled schemes (including SolArk if no DC) have the problem that if loads drain battery, system shuts off and PV can't recharge it. Also if load exceeds PV during the day, battery drains.
Having a generator around for dark start or practicing how to adjust the low voltage / low SoC cutoff mitigates this.
As well, even with a DC-coupled system you need a dark start procedure written down (and potentially support hardware to bootstrap) if you have Rapid Shutdown.
i do not really have space at house (feeding main service panel) for this so am exploring the barn
Hmm. Another idea if the space is constrained in the house is to pull a new #1 feeder from the barn. And manually switch the house to this if power is out.
Or put in a shed near the house to hold batteries and inverters.
You can pull CAT6 at this time too for control connection (200ft is really long though, you might need official RS485 or whatever cable). At this distance you might want to use a digital energy meter instead of sending an analog CT signal that length. I don't know what the limit is of analog CT but 200ft sounds like a lot.
Don't know how far away CT are allowed, but CT before barn panel could seek to supply barn loads. CT before house panel could seek to supply all loads.
CT before house panel would have better ROI for the system.
As I said above need to contact manufacturer to see if they recommend analog or digital.
Would Absolutely consider going that route I believe you had helped me determine that 3800 watts would be my maximum solar on barn given the 100 amp main panel and 60 amp backfed breaker? Would sincerely appreciate opinions on panels and GT inverter if I were to go that route.
I think you can go up to 100A total with no service upgrade, so that is 19.2kW AC (subtract out your current system). And you can overpanel DC vs AC to stay below 19.2kW. For instance, if you put 40kW of solar panels but limit export to 19.2kW. In the summer you will throw away a lot of production during the peak of the day, but your extended hours production goes up.
If allowed by POCO (electrical code allows it) you can add a 70A line side tap leading to a breaker older or small subpanel with 70A breaker in it. Then move the barn feeder over to this box.
(This is assuming your existing is a 30A breaker on the line side tap. Or is it 25A?)
The 200A upgrade is potentially straight forward. They could put a 200A panel next to your meter, and then feed your current main from that.
If you already have a 200A capable meter base, you can potentially just upgrade the conductors from meter to main to allow adding up to 200A of backfeed breakers.
how do we get 160 amps drawn in that scenario? ( wouldn't 100Amp main service panel breaker trip?)
The 160A is the hypothetical max backfeed (80% of 200A) if you upgrade the path to the POCO to 200A.
The 160A will never get pushed into your main (can still be protected by 100A). The main will only draw as much power as the loads want.
I'm not sure if 60A breaker to barn is allowed when backfed with PV. Does the rule consider the 20A breaker used for PV in barn? Or the 60A breaker in main panel? Possibly you're required to replace with 50A breaker.
Most of the clauses for bus calculations use the actual output nameplate amps (some don't and use OCPD). A lot of designers I think just use breakers as shorthand.
