Shading question.

Seven

On my house I will initially be running 4 strings of three panels each. The entire array will be 12 panels, portrait orientation, in a single line across my roof. In the early morning a small portion of my roof gets shading from a neighbors tree. It looks like two of the last panels will be shaded until about 8am.

My question is that if that string has some shading will it be bad for the controller? Classic 150. The output of that string will be less than the other strings that are in the same combiner box. I am ok with that, I just don't want to do any damage.

Side question. Being the panels are roof mounted, does the combiner box need to be on the outside of the house or can it be inside next to the other equipment?

Cariboocoot

Re: Shading question.

Shaded panels just drop power. The charge controller won't care; it just won't be able to put out as much.

Usually you put the combiner close to the panels so that you only run one set of wires down to the controller. But you don't have to. In some cases it may be advantageous to run multiple lines to the combiner near the controller - depending on the distance and wire sizes needed to handle the Voltage and current with minimal loss. Electrically it makes no difference if combined here or there, so long a the wires involved on both sides of the combiner can handle the respective loads.

waynefromnscanada

Re: Shading question.

And one very important thing to remember - - trees grow, so the shading problem is only going to get worse!

Seven

Re: Shading question.

Thank you both.
I never thought about putting the combiner box in the attic or on the roof. I just wanted it easy to access. The way my roof is, I could put the combiner under a overhang on the west side and be able to access it easily if I was already on the roof. What is the normal gauge of write that will take the mc4 connector? I will be running 90voc from my strings.

Already talked with the neighbor and he is all for trimming his tree, as long as I pay for it. Lol
I have a buddy that does trimming for a living, so I will be giving him a call. If my understanding is correct, the shading I am now getting will be less in the winter with the sun lower on the horizon. The tree in question is due east of my panel location

drew4justice

Re: Shading question.

Seven wrote: »

Thank you both.
I never thought about putting the combiner box in the attic

Keep in mind that if you run wires through the attic the solar heating of your roof will elevate the temperature in the attic and derate the ampacity of the conductors. Not sure, but I believe you may need to run the wires in a metal raceway if you're trying to stay up to code?

Just my $0.02.

Drew

Seven

Re: Shading question.

I understand what you are saying. Yes, it must meet code. I am seeing conflicting things in the code about it, but I have a month or so before I am ready to install everything, so I will get it figured out. I don't think that the attic would be any hotter than running the wires on top of the roof. Any conduit they would be in would be in direct sunlight on top of the roof.