Planning Phase of first DIY Solar

[oaknut]

Hello, this will be my first post but I have been trying to read as much as I can. I have a plan to install a 23kw grid tie system that will power two homes. Here in PA we have virtual net metering so to my understanding we will take the solar to one house and the excess will offset the power in the 2nd home as long as they are both in the same persons name for the electric bill. I plan on using 50 480W panels. I want to install them at about 28 to 30 degrees from what I found on PV watts unless someone else has something to say. I question this myself because my latitude is around 41.45 degrees. The though I am having is because this is grid tie, this will give me the best output through the year.
If I can find them I would like to use two 12.5kw Fronius inverters and tie 2 string on each inverter. Here is where I would like some input. From the two inverters, I am not sure what to do next. I have a run of about 250'. Is there a way to combine the two inverters in a junction box or a breaker box or does this mess with the phasing or not allowed due to some code? If I do this, I assume I would double the amps from a max of 52A up to 104A. I would also have to go with a heavier gauge wire. If I am unable to do this, I will just run the 3 wires from each inverter to a fused AC disconnect near by main meter and then do a line side connection. By combining them I would only have to run 3 wires the 250' vs 6. Due the the gauge of wire, I am not sure of the cost savings if any at this point, hence why I am asking if I can even do this. I have a 200amp panel so I would be unable to tie into it due to the 120% rule.

If you are able please help me determine the best and most effective way to get from the inverter to the grid that would help me a lot. Is the fused disconnect an acceptable idea to protect the system or do I use breakers instead of the fuses? The inverters require an 80A over current protection device. Thanks for your help and I appreciate reading all the comments out there.

 

[400bird]

Yes, you can combine the AC side and run both inverters on the same 4 wires. You cannot do this in the PV side. All the MPPTs and inverters need dedicated runs to their panels.

 

[SilverbackMP]

I had 240’ of run and went high voltage DC to the inverters rather than converting closer at the panels. But my inverters (Sunny Boy) accept up to 600v on each string (three inputs on each inverter, I used two) so I was able to squeeze 12 of them into series (total of 72 panels). Very little line loss and LOT smaller wires. I laid two runs of 2 1/2 inch conduit and I can easily triple the amount of panels in the future if I want (currently using 1/2 the capacity of one line of conduit).

Anyhow, point of the diatribe is not to discount the benefits of running higher voltage DC over longer runs.

 

[oaknut]

I had 240’ of run and went high voltage DC to the inverters rather than converting closer at the panels. But my inverters (Sunny Boy) accept up to 600v on each string (three inputs on each inverter, I used two) so I was able to squeeze 12 of them into series (total of 72 panels). Very little line loss and LOT smaller wires. I laid two runs of 2 1/2 inch conduit and I can easily triple the amount of panels in the future if I want (currently using 1/2 the capacity of one line of conduit).

Anyhow, point of the diatribe is not to discount the benefits of running higher voltage DC over longer runs.

That is a good point I never thought of, I need to look into that. Thanks

 

[oaknut]

Yes, you can combine the AC side and run both inverters on the same 4 wires. You cannot do this in the PV side. All the MPPTs and inverters need dedicated runs to their panels.

So I could run each inverters to their own 80A breaker then the panel to a ac disconnect near our meter before a line side connection? I am asking because I was told I could not but did not understand why. So maybe they were wrong

 

[400bird]

So I could run each inverters to their own 80A breaker then the panel to a ac disconnect near our meter before a line side connection? I am asking because I was told I could not but did not understand why. So maybe they were wrong

You likely need another breaker near the source for the line side tap. Depending on code in you region, you might need to have these as two separate components (knife switch and breaker) but the inverter would be fine with the breakers serving both functions (over current protection and safety disconnect)

If I am understanding correctly it will work for the inverters. Might not work for code.

Line side tap > breaker> AC disconnect (knife switch might be required) > long, heavier gauge AC run > two AC breakers > short, lighter gauge run to each inverter

 

[oaknut]

What I was thinking is a fused ac disconect. If I do that, I should not need any other components. The inverter does not need any dc fuses or breakers.

 

[400bird]

What I was thinking is a fused ac disconect. If I do that, I should not need any other components. The inverter does not need any dc fuses or breakers.

The fused AC disconnect sounds good.

I'm pretty sure you need a DC disconnect to meet code (and for serviceability reasons)
Correct, thrt PV wiring doesn't need OCPD as long as the PV output amperage is within the rating of the wiring and panels (counting all parallel strings)