Amp input Question

[BigTXSun]

I am in the beginning stages of a Solar Build. As I research and learn about setting, the inverters have limits. Typical is a 600V input and a max amp input of 16–18. All this is dependent on inverters, but those seem to be common. It looks like I will need 20 panels. Again, depending on the panel size (but I was looking at the big ones from mission solar), 10 panels in series adjusted for temperature is over 500 volts. That will meet the inverter volt limit, but when I tie the other 10 panels in parallel, that will push me over on the amp input. Each panel is a little over 11 amps, so it doubles when I tie them together.

Like I said these are general numbers and change based on panel specs but it appears it is difficult to meet the specs of the inverter at 20 panels. My questions are

1) Can you solve this or do you have to accept clipping. If you accept the clip, what does that do for your overall output. Lots of money to not get full use.
2) Is there another way ....What am I missing.. can not be the only one designing a 20 panel system

I suppose I could get another inverter but that is costly.

Thoughts help etc

Thanks

 

[BigTXSun]

When i get everything together I will post the build under another thread but wanted to ask some questions separately so it is easily searchable.

 

[JWLV]

You don't have to worry about the amperage from the PV panels. The inverter's spec is just to let you know how much current it can use. If more current is available, it just won't use it.

 

[BigTXSun]

Thanks JWLV -- I understand, but would that not hurt efficiency. It seems like you would be spending lots of dollars on equipment that is not working for you or is this just the way it is. To get to 11KW it is going to take fair number of panels. 11KW is my net zero number.

Also if I understand the inverter specs most only allow 600V max. I am assuming that means that you need to control the volts going to the inverter to ensure it is under 600V otherwise you shut down the inverter at best and at worst fry it. Correct.

 

[JWLV]

If 600V is the max for your inverter, it's best to stay about 10% or 20% below that. VOC specs on a PV panel is based on Standard Test Conditions (STC). STC means that it was tested at 25 degrees C. If it's hotter, the VOC will go lower. If it's cooler, the VOC will go higher. If where you live gets freezing temperatures on some days, you'd be wise to stay below 500V. There is a formula and a few websites that can help you estimate VOC based on temperature. I don't have them handy right now. Maybe someone else can post it.

Every SCC/Inverter has a max PV input voltage and amperage. The trick is getting the most out of your PV panels while conforming to that maximum. If you go over the voltage, you'll fry the SCC/inverter. If you go over the amperage, not much will happen, but then you are not utilizing the full potential of your PV panels. To find the right combination for your system, you'll have to do the math and come up with a good combination of serial & parallel layout to fit your needs.

 

[gotbeans]

Also if I understand the inverter specs most only allow 600V max. I am assuming that means that you need to control the volts going to the inverter to ensure it is under 600V otherwise you shut down the inverter at best and at worst fry it. Correct.

You don't control the voltage in
You have to make sure your panels in series add up to.. around 480-500 so you're safe at 20% less otherwise when it becomes freezing and super sunny your panels may go above rating and kill your charge controller

 

[DougfromdaUP]

The clipping you’re worried about won’t happen too often. You’ll be well below the rated output with your panels baking in the Texas sun most days.
And the rest of the time those extra panels will be providing more power.

Do you look for a #13 wire if a #12 has 1% too much ampacity ? No, there would be no savings.

 

[BigTXSun]

Thanks. I have been researching a ton on here and also using "The Google" That is kind of what I figured. I just hate to spend dollars that are not working to their maximum capacity.

I am planning a Grid Tie. Texas has good net metering and even the ability to sell back but I just mainly want to lower my electric bills. Selling back is okay if it happens. The down side is when the power goes out, but I have a generator with a manual transfer switch for those occasions. I do worry about the small blips in power, given that I am in the country. I worry that it would just shut down, and then I would be solely on the meter till I caught it, and again, the solar is not working for me.

I took a look at the Growatt inverters, I believe it is the 6000 model, and they look simple and easy to install. I would just have to run two of them for the 11 KW. The good thing is that I could start small and then just add on as money presents itself. I do not want to get a loan and want to pay for this as I go, BUT to make the tax credit work, I need to get a big enough system to start with and start saving money on my electric bill. 6 KW might be the ticket with 1 Growatt.

I want to DIY it all the way to the point of the meter hookup, then let an electrician take over. I think the companies require that anyway.

I will start a new thread when my research is more mature on the total system and specs with brand and model numbers to see what the forum thinks. This question was to help me get over some details for that thread.