Thread: Ben's Garage
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Old 02-19-17, 05:19 PM   #91
bennelson
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Join Date: Sep 2008
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Thanks for the advice, Steve.

Yes, in general, everything you are saying is about what I was thinking on this system.

The advice on shoes sounds good, and I'll take it.

As for the "center-feed" on the Enphase inverters, I had already read the document about it, but I'm not sure how I would actually execute it.

With 24 panels, I need two strings of inverters. That could be 16 panels on one leg and 8 on another, 12 panels on each, or any variation in between. I DO need each circuit going to a 20A breaker.

Looks like the best way to do that will be to bring down each circuit from the roof to a combiner box on the exterior wall of the garage. I am required to have an outside AC disconnect anyways. I'm looking at the Midnite Solar NMPV6 AC Disco. It's a combiner box which can support up to three double-pole (240V) circuits AND it has a big red lockable disconnect. (The big red lever actually physically flips the circuit breakers inside!)
https://www.altestore.com/store/encl...P77xoCD_zw_wcB

By using that, I would only need one box on the side of the building instead of two.

Getting back to center-feeding.... My array will be 8 panels wide by three rows tall. It's pretty easy for me to do one circuit of 8 and the other of 16 because that brings the ends of the cables out from behind the solar panels to a roof junction box. It would simply mount on the end of the racking.
If I wanted to do two circuits of 12 and 12 panels. I'd need the junction box UNDER the solar panel right in the middle of the roof, where I'd never be able to get at it again, and then run conduit from the center of the roof (under the panels) out to the edge, around the edge of the roof, and down the side of the building.
And that's not even center-feeding, it's just making both circuits the same length!

To do a true center-feed, I think I'd have to be running the Enphase trunk cable VERTICAL, or in a "swirl" pattern to get one half the roof to a junction box, centered in the middle of the left half of the roof, repeat on the right half of the roof, then run conduit from both boxes all the over to the edge of the roof. Seems like it gets complicated fast!

I might have to shoot a video with some diagrams to get some input on the best way to do this. Ideally, I'd prefer NOT to have ANY junction boxes or the like on the roof UNDER the panels. If there's EVER ANY reason why I would need to get at one, it would require removing a signfificant portion of the solar panels to get at the box.

Maybe I could have the one circuit be the full 16 panels, but center-feed that one. That way, the junction box could still be on the END of the array NOT under a solar panel. That could feed down to the other box to join the other circuit of 8 panels, and from there to go down the side of the building to the Combination Combiner/AC Disconnect.

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