I don't think it is really called a line-side tap when it comes after the first OCP.
My old place was already set up that way, a 200A main breaker and meter in one box. New place I'm upgrading to 200A and doing the same (200A main breaker only panel, fed by a meter box.)
I don't feel at all bad about smaller gauge wires protected by OCP at the far end, so long as the wires are as large as required ground wire for the upstream protection. If there is a moderate overload, so wire heats up for a while until it clears, that will be through the downstream OCP. If there is a dead short in between which fast strips upstream OCP, required ground wire is of sufficient size.
For my 200A, that would be 6 awg copper. Yours is 400A (fast trip above 2000A, or whatever your fuse curve), so 3 awg:
brunsengineering.com
From what Tim says, "40A" is considered sufficient. I guess that means 8 awg, since 10 awg has 40A ampacity but is only allowed 30A. Since it is inside conduit, other things are protected, but would rather avoid insulation damage.
But I might want to second-guess the code and go larger. In my case, couple of 100A branches will be 2 awg (plenty large), and 8 awg ground is considered sufficient but maybe I'll follow my reasoning and use 6 awg for ground.
I think main problem would be poor contact to conduit, which would be more resistive than copper and could have poor contact in places. If series resistance dropped current below 2000A, then it would flow a while. Again, fuses have their own characteristics different from breakers.
BTW, if anyone is in the Houston area, my local solar distributor is selling these panels at a great price of $70 each.
Please do, $0.19/W is a great price. Bunch of us bought from Inxeption for that price delivered, but that deal is sold out.
Also, the inverter will be right next to the house panel and I will also be adding a manual transfer switch and critical loads panel, but they will all be within a few feet of each other so any potential upgrades should be easy compared to this installation.
Interlocked backfed "generator" breaker in the house panel would let you manually supply any load from inverter.
Another one in critical loads panel would let you bypass inverter if it is down. Of course you'll also have OCP/disconnect before the inverter. Transfer switches are more expensive and often larger, but just a fused safety switch should work here.
Not sure I understand the question. It doesn't need any accessories that I know of after reading the manual. There is no mention of an autotransformer or transfer relay.
Some brands/models are 240V only, and some don't have relay separating grid input from output. If yours is 120/240V it probably contains everything.
And it will be nice to have a transfer switch for the following reasons. I will have a backup battery, but if the grid goes down, I don't necessarily want all the critical loads to come on automatically so I will use a manual transfer switch and then I can manage the critical loads. Another reason is that my backup battery will only be 10kwh. After a day or so without sunshine it will depleted.
You might want automatic backup of critical loads, like communications and alarm. Of course those may have 12V supply, could run off a battery, charger, PV panel.
The Growatt doesn't need CT's to operate, from what I understand. It is an optional accessory that only provides data to the app. I may get one eventually, but I'd probably have to run separate conduit for that. But you bring up good points that I haven't thought of. I would probably install the CT's on the line side of my multitap, as you suggest. But since they may not fit on the 350 wire, what would happen if I installed them on the 2/0 going to the house? I'm guessing I would just get inaccurate data?
Will you have a net-metering plan?
Without that, you could only feed downstream loads (protected loads panel).
But if you install CT just before junction box, then inverter can backfeed to house and barn, without backfeeding grid.
If you have net metering, no need because you can backfeed both house and grid freely.
If the plan gives less than 100% credit, you might want to measure backfeed and enable loads to use surplus (for full value rather than reduced credit.) Maybe with other meter/control not related to inverter.
If you have time of use, CT could tell inverter to charge battery rather than exporting during low rate times, discharge battery rather than importing at high rates. Assuming it implements such functions.
