Panel wiring

[Dave T]

I picked up a 4KW PV system. Previous owner had gathered the equipment other things happened, and he had to get rid of it.

I have a lot of electronics / electrical experience, just not specific to this big of a system.

A couple of questions:
I have Sharp ND-224UC9BX panels. When wiring in parallel, can they just simply be wired + to + to + / - to - to - etc.? If one panel gets shaded, would the power from the others harm the dark one? [Do they need diodes to prevent backflow?] Fuses? Each panel, or a big one at the main tie point?
When wiring them, how important is keeping the resistance of each run to each panel / group of panels equal?
I am in central CT, what angle is optimal for a fixed mount facing south?

Thank you,
Dave

[sensij]

Without knowing to what you are wiring the panels, it is hard to know how you should wire them.

Check out PVWatts for mounting angles, and read the help files for more information on the technology you've just acquired.

[Dave T]

I also have these:

19 Sharp ND-224UC9BX panels
Outback Flexmax 80
Outback GVFX3524 inverter
4 Powerjack PSWGT inverters

[ButchDeal]

I also have these:

19 Sharp ND-224UC9BX panels
Outback Flexmax 80
Outback GVFX3524 inverter
4 Powerjack PSWGT inverters

19 is an odd number of modules to string up. 18 would do better with 6 strings of 3 probably being a good fit. You would need some fuses a combiner etc.
biggest problem is that the inverter is 24v and the charge controller flexmax 80 is only 80 amps. 4kw at 24v is way too many amps for it.

The outback inverter is grid tie bimodal. You will need a 24v battery bank to use it. And another flexmax 80 to handle the array.
i would toss or sell the powerjacks though.

[Dave T]

Yes 19 is a weird number. One was damaged in shipping to the original owner, he would have had 20.

I am going to look at selling or trading the 2 outback pieces for a good grid intertie inverter. Adding the expense of a battery bank makes no sense in my situation.

[ButchDeal]

Yes 19 is a weird number. One was damaged in shipping to the original owner, he would have had 20.

I am going to look at selling or trading the 2 outback pieces for a good grid intertie inverter. Adding the expense of a battery bank makes no sense in my situation.

That outback,inverter is a grid tie inverter. It is bimodal but grid capable. He G in GVFX is for grid.
you would save on batteries though with a grid tie instead of bimodal. I would suggest solaredge hdwave SE3800H with p300 optimizers. Takes care of your shadows and most of the safety and code requirements.

[Dave T]

I looked up the SE3800H. Sounds very good. Says it wants nominal 380V DC input. The open circuit V [or even 24V] for 19 panels is 695, which is over the max.

The p300 optimizers, I am not sure how they are used? One per panel? Outputs in parallel? Do they make the 24V from each panel into the 380 nominal the inverter needs? The spec sheet says they only make 60V output to the inverter.

[ButchDeal]

I looked up the SE3800H. Sounds very good. Says it wants nominal 380V DC input. The open circuit V [or even 24V] for 19 panels is 695, which is over the max.

The p300 optimizers, I am not sure how they are used? One per panel? Outputs in parallel? Do they make the 24V from each panel into the 380 nominal the inverter needs? The spec sheet says they only make 60V output to the inverter.

You put one optimizer per pv module. The optimizers have a buck/boost in them to regulate the output voltage.

[Dave T]

Is there a way to use the panels and the inverter without the optimizers? What would the output / collection difference typically be? Any shading losses on part of the array will most likely be near start and end of day, so the percentage would be small. I may not gain enough to justify the cost of that many optimizers. I saw bigger optimizers, looked like they could handle 2 or 3 panels in series?

Is there someplace I can find some typical and various system configurations?

Thank you for the help.

[ButchDeal]

Is there a way to use the panels and the inverter without the optimizers? What would the output / collection difference typically be?

Without the optimizers the production would be zero.

Any shading losses on part of the array will most likely be near start and end of day, so the percentage would be small. I may not gain enough to justify the cost of that many optimizers. I saw bigger optimizers, looked like they could handle 2 or 3 panels in series?

Is there someplace I can find some typical and various system configurations?

Thank you for the help.

The larger optimizers can handle two pv modules but only work with 3 phase inverters.

[Dave T]

Started looking through the other suggested inverters -this one looks like it could do the job without a bunch of extra expense? Fronius Primo 3.8-1 208-240

[sensij]

Started looking through the other suggested inverters -this one looks like it could do the job without a bunch of extra expense? Fronius Primo 3.8-1 208-240

It gets a little bit complicated. Simple string inverters like what SMA sells and the Fronius you found require the panels to be wired in series strings to generally get to 200-500 V. Your panels have a Vmp of 28.9 V, so a string of 10 into one mppt input and a string of 9 into the other is probably what would work best. The extra expense that comes with those inverters is a "rapid shutdown system", which is a safety system that became required as of 2014 NEC.

The Solaredge system has a single inverter, and an optimizer on each panel. In that system, the panels each operate independently, and you can have all 19 optimizers in a single string. The optimizers coordinate to provide the proper DC string voltage for the inverter. Because each optimizer is capable of shutting down its panel, you don't need the external safety system required for basic string inverters.

The 3rd common option is to install a microinverter for each panel. These convert to 240 Vac right at the panel.

With the rapid shutdown system, the cost for the string inverter is usually pretty close to the cost of the Solaredge system (optimizers and inverter combined). Microinverters tend to be slightly more expensive, but can be easier to install, and with only 224 W panels, you could look for a deal on some enphase M215's.

Any of the systems that put electronics on each panel introduce reliability risks that string inverters don't have, and you'll find lots of opinions about which type of system is superior and why. Do your research, and choose what you think is best.

[ButchDeal]

Started looking through the other suggested inverters -this one looks like it could do the job without a bunch of extra expense? Fronius Primo 3.8-1 208-240

Looks are deceiving. Add the rapid shutdown equipment and there is your extra expense.

[Dave T]

Ah, this is making more sense now.
Sounds like the solar edge optimizers outputs are wired in series?

I'll look at the micro inverters too..


Thank you!

[ButchDeal]

Ah, this is making more sense now.
Sounds like the solar edge optimizers outputs are wired in series?

I'll look at the micro inverters too..


Thank you!

The solaredge optimizers are wired in series or sereies/parallel

Micros appear cheaper at first but they have a rather expensive cable that is required, most miss the cost of the cable.