IQ aggregator or soladeck for trunk wiring

[joemadsun]

Hi,
I'm in the planning stages for a ~18 panel IQ7+ installation. The IQ7+ branch limit is 13 microinverters so I will need two branches. I would like to center-feed the branches as recommended by enphase to minimize losses.

I am looking to get opinions on using an IQ aggregator versus a soladeck versus keeping both branches independent until near the AC disconnect near the meter.

IQ Aggregator
Wire Q cable at center into IQ aggregator. LFMC conduit from IQ aggregator to soladeck, soladeck just acts as a pass-through, 6 gauge wire in 3/4" EMT conduit through attic down to utility room and out to garage(panel in garage, meter outside of garage)
Pros:
The IQ aggregator provides nice Q connectors on the outside so no need to use Q field wireable connectors.
Fuses inside the Q aggregator less likely to blow than breakers?
Only 3 wires(2 current carrying + 1 ground) back to AC disconnect
Cons:
OCPD under panels, if issue comes up, panel has to come off
Still need a soladeck to make rooftop to attic transition

Soladeck with internal breakers
Create two stub cables with field wireable Q connectors that wire through glands in the soladeck. connect these cables to center connectors of each branch. wire to 2x 20A breakers in soladeck and then run 6 Ga cable through 3/4" EMT conduit through attic down to utility room and out to garage(panel in garage, meter outside of garage)
Pros:
Simple solution. Q cables feed into soladeck, soladeck has 2x 20A breakers internal to it
only 3 wires(2 current carrying + 1 ground) back to AC disconnect
Cons:
Circuit breakers more likely to trip than fuses?
OCPD under panels, if issue comes up, panel has to come off
Have to used field wireable Q connectors

Soladeck with combiner box near AC disconnect
Create two stub cables with field wireable Q connectors that wire through glands in the soladeck. connect these cables to center connectors of each branch. wire to DIN pass-through connectors and use 8 gauge cable to run both branches back to combiner box in garage via 3/4" EMT conduit
Pros:
No OCPD on rooftop
Technically lower loss as splitting the branches across 8 gauge wire is lower loss than running both branches on 6 gauge wire
Cons:
Need 5 wires(4 current carrying + 1 ground) back to AC disconnect
Need a juncitonbox somewhere in the garage to do the combining versus using an already availabel junction box(soladeck)



What are your thoughts?
1. My order of preference would be Soladeck with internal breakers seems the most clean, but then I have OCPD devices on the rooftop that could trip. Would you be concerned about that?
2. IQ aggregator is similar to the soladeck with breakers, but enphase designed it so I assume the fuses will never blow unless there is truly an issue.
3. Soladeck with combiner box in garage results in lower loss but its on the order of 0.1% less loss so really insignificant overall.

[bob-n]

You have three good options. At this point, it's just preference.

If it were me, I'd go with #3, so that the breakers are at ground level. The less you have on the roof exposed to the elements, the better.

Option #3 also helps if you ever have to debug a problem, because you could separate the two strings at ground level. But that's a really tiny advantage. Your Envoy gateway will tell you so much about each panel and each microinverter. Most of the time, you won't have issues. On that 1 in a million chance that you have a problem, the Envoy may tell you all you need without separating branches.

[joemadsun]

Thanks,
That does seem like the safest solution in terms of avoiding any problems that would require removing panels. Also probably results in the fewest junction boxes, since the combiner box will have the envoy in it rather than needing an independent box for the envoy.

[ChrisBarrett]

Joe,
Which setup did you end up going with? I have a similar conundrum but plan on center feeding from the soladeck. I'm also in Madison WI!

[joemadsun]

Hey, I ended up going with the IQ Combiner method with a pass-through soladeck on the roof. I figured I need a place to put the envoy anyways so might as well buy a box with the envoy installed in it. Also was leery of putting something that is meant to service(breakers or fuses) some place completely inaccessible(under panels on the roof).

[ChrisBarrett]

Nice! Also - did you install DIY? Curious if you ran into any inspection problems.
Thanks!

[joemadsun]

I am in the process of DIY install. I got my permit a week ago and equipment is arriving currently. I had to add some additional rail mounting points to common trusses in my roof due to calculations from solarstruc spreadsheet that the city of Madison uses to calculate stresses in trusses. We'll see if I run into any inspection issues, but I expect it will be a while until my first inspection.

[ChrisBarrett]

great! I'm about to apply for the city permit, and do the documentation for the utility. Did you purchase a special crimper tool for the Q cable connectors?

[joemadsun]

I did not buy the crimper tool. Where I work has a variety of crimp tools so I figured I can make one of then work. Worst case I will crimp with a pliers and solder.

[Mike90250]

....... Worst case I will crimp with a pliers and solder.

Yep, that's about the worst you can do. Proper crimping provides stress relief on the cable, Solder very often wicks up the strands under the insulation and makes a solid wire. A bit of play and vibration over the years and the stress of the flex wire at the edge of the solder wicking, and the wires break under the insulation. Or if the crimp is bad enough, under heavy load the solder melts and the wire falls out, with solder splashing and plasma arcing. fun fun fun

[ChrisBarrett]

Thanks for the warning Mike. I have some general crimping tools that should do the trick, so no worries there. Meanwhile, Joe if you get to your install before me - could you post up some pictures of how you wire the center feed? I just received delivery of all my components and I need to figure out the wiring scheme for each of my arrays.

[joemadsun]

Here is a super crude drawing of my wiring. Red box is the soladeck. Blue is the Q cable. Not shown is the pigtailed female Q cables coming out of the soladeck to connect up to the Q cable.So 8x panels in the left branch and 9x in panels in the right branch

https://ibb.co/51wwp3B

And I was able to find a crimper at work that made a nice crimp

https://ibb.co/M5fkyDK

I have installed the racking and am waiting on a rough electrical inspection before proceeding to installing panels.

[nova42]

HI there - came across the very helpful post while researching design of my own system. I have a question about combining branches in the soladeck.

system info (picture below):
I am planning a 42 panel system with enphase inverters consisting of 5 branches/strings of panels on 2 seperate roof sections, using a soladeck box per roof section. I wanted to combine all strings on each roof section to minimize the number of wire runs back to the Enphase combiner/envoy box. Similar to poster's option 1 and 2...

however, I do not understand the need for breakers/ fused connection on the roof if everything is going to be routed down to the breakers in the Enphase combiner box. Seems the AC combiner kits or IQ-Aggregator are pretty expensive and I would need 2 seperate AC combine kits. Is it not ok to simply tie the 3 branches together in a standard (non fused) junction box on the roof?
solar panel install.jpg

[ChrisBarrett]

You don't need breakers on the roof, afaik, as long as you are not switching from DC to AC right there, for example. How many branches you can combine depends on their total amperage and the gauge of the wire running to your combiner box as well as the breakers used in the combiner box.

[Mike90250]

With your connections and splices being made under shelter ( in the attic ) I would suggest using #4 or #2 aluminum wire. Less cost, reliable if done right with anti-ox and easier to handle.
The vertical feeds from the horizontal arrays, needs to be larger than #12 copper, I suspect.

And you are using micros because why ? Rapid shutdown ? Shade issues that can't be solved ?