# Solar problems



## jjh81 (Aug 17, 2010)

So here we go I thought I had a grasp of things now I'm lost. I have 36 75 watt 12 volt solar panels. 2 of which are wired in series to make 24 volts which makes 18 24volt panel sets. Which means in essence I have 18 24 volt panels. Im trying to wire these up to keep 24 volts and not go over amps. should they be wired in paralell or series. I think Ive been out in the sun to long and cant figuer this out I need three sets of 6 to go to my combiner box. The panels are Siemens SP75-CPL got a great deal on them. Panel specs are in the pic. Also if it matters I'm running a midnight solar 150 charge controller.


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## shawnlee (Apr 13, 2010)

Series doubles voltage...parallel keeps it the same.


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## jjh81 (Aug 17, 2010)

That's where my mind was but I couldn't keep it straight in my head 3 day of triple digit heat out here.


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## wy_white_wolf (Oct 14, 2004)

If memory serves me the Midnight classic 150 has a max voltage input of 150V. Derating 25% for cold weather and high light conditions lowers that to 120V. So you can run 5 panels in series to the controller. If you happen to live down south where the derate is less you might get by with 6. 

WWW


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## jjh81 (Aug 17, 2010)

So can I run 3 legs of 5 and 1 leg of 3?


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## Murby (May 24, 2016)

Go for the highest voltage your controller can take to reduce voltage drop losses.
Your Midnight Classic 150 can take 150 volts max at 96 amps.

36 panels means you want 6 parallel rows/columns of panels with 6 panels in series.

This configuration uses all 36 of your panels and the fewest number of connectors and wire.

Here you go:









EDIT: Hold for a moment, have to check something...

OK, the above array will work but it might put you close to over voltage on cold days.. So with that in mind, I would suggest a 7 x 5 configuration as follows:

This will use 35 of the 36 panels with fewest number of connectors, wire, etc. You get a spare panel in case you get a malfunction. 

I'm not sure why you want to keep your system at 24 volts as you said, your charge controller will knock down the voltage to whatever charge settings you set it up for. When it knocks down the voltage, it will drastically raise the amps. 

35 panels at 75 watts per panel works out to a 2625 Watt Array. That's 2625 watts of battery charging.. Hope you have a decent size battery bank to suck all that up..


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## Murby (May 24, 2016)

Let me add that you could go 4 in series and 9 in parallel, but you're going to spend a lot of extra money on wire, conduit, and combiner boxes.. You'll have to jump to a wire that can handle 45 amps.. and then, since you're only at around 68 volts, you'll need to go one size larger to avoid voltage drop losses. 

The most efficient setup, when all things are considered (electrical, cost, maintenance, etc) , is the 6 x 6... but if it gets cold where you're at, the next best is the 5 x 7 to array and leave a panel to spare.

Going to a 4 x 9 would use all the panels but will cost extra.. you either spend it up front in big wire, or incur the wrath of the laws of physics with voltage drop losses.


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## jjh81 (Aug 17, 2010)

I live in northern nevada it can get cold 20 or 30 degrees sometimes lower here these panels are mounted in sets of 2 already wired in series that is why I was thinking parallel. But I'm not sure now. And the reason im going 24v is everything i have is 24 volt. I was looking at other panels when I bought everything else.


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## MoonRiver (Sep 2, 2007)

jjh81 said:


> I live in northern nevada it can get cold 20 or 30 degrees sometimes lower here these panels are mounted in sets of 2 already wired in series that is why I was thinking parallel. But I'm not sure now. And the reason im going 24v is everything i have is 24 volt. I was looking at other panels when I bought everything else.


Your charge controller works with 12 to 72 volt batteries, so the input voltage from solar panels to charge controller does not dictate output voltage to batteries. (If I correctly understood your concern)


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## jjh81 (Aug 17, 2010)

No my inverter and battery bank are 24 volt


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## Murby (May 24, 2016)

The diagram(s) I gave you are your best bet. The purpose of your charge controller is not just to charge the batteries, any stupid and inexpensive PWM charge controller can do that... You spent the big money on your Midnight Classic because its a high power MPPT charge controller.. 
I'm an electrical engineer by education and fighting the urge to give you five pages of explanation on the difference.. but lets cut it short and just say an MPPT controller is to a cheap PWM what a bicycle is to a Harley Davidson.. Its barely even the same thing.

Your Midnight controller will take whatever voltage your panels put to it (up to 150v), and convert it down to your battery voltage.. When it does that, it (in simple language) trades voltage for amperage.. so the voltage goes down, but the amperage goes way up.. The 30 or so amps going into your controller at 120 volts will get converted to around 24 volts at 60 or 70 amps.. Amps are what charge your batteries, not volts.. the volts are just there to push the current(amps) through the wire.

And you want as many volts as you can get coming out of your array.. the higher the voltage, the lower the current, and its current that causes wasted energy.. When the current level approaches the capacity limit of the wire, energy is converted to heat and dissipated to thin air.. (quite literally what your kitchen toaster does).. Granted, your wire isn't going to glow red or anything, but any heat generated at all, even less than what a human can feel, will be lost energy.. For the sake of simplicity, we won't go into the EM energy loss on top of the thermal losses. Its not a big deal when the giant monster power grid is feeding your home, but it is a big deal when you're trying to squeeze energy out of sunlight.



jjh81 said:


> I live in northern nevada it can get cold 20 or 30 degrees sometimes lower here these panels are mounted in sets of 2 already wired in series that is why I was thinking parallel. But I'm not sure now. And the reason im going 24v is everything i have is 24 volt. I was looking at other panels when I bought everything else.


The physical orientation and layout of your panels means almost nothing.. Just run the wires from panel to panel as shown.. The more organized the physical layout, the less wire you'll use doing it. 

Be sure to use PV wire and MC4 connectors.... this is important as the PV wire is rated for outdoor use. You're dealing with high enough power to kill someone or start a fire so don't screw around pinching pennies. DC power is much worse than AC power when bad things happen.

Unless your charge controller is mounted 15 feet from your panels, I would suggest you take whatever current your array will generate and pretend to double it for the wire size.. 

And don't forget to install circuit breakers, you need the following:
Array >>Breaker >> Charge controller
Charge Controller >> Breaker >> Batteries
Batteries >> Breaker >> Inverter

And if your inverter puts out more than the wire that feeds your appliances then you need normal household breakers protecting those as well.

Ebay is your friend.. DC Breakers are easy to find in all different sizes. Remember, the breakers and fuses protect the wires, not the crap plugged into them.

Its easy to find normal household breakers and panels on Craigslist as well...


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## jjh81 (Aug 17, 2010)

Ok so I was wrong on one thing I thought we had gotten the midnight classic 150 but I actually have a classic 200 so if I have everything correct I can run the 6 parallel rows/columns of panels with 6 panels in series and not go over the voltage when its cold am I correct? Also Murby I really appreciate all your knowledge and not just throwing up your hands and being like his guy is an idiot cause its how I feel about now.


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## Murby (May 24, 2016)

No problem, glad to be of help.

Looks like the 200 has a higher voltage limit so the 6 x 6 config should work well.. 

What is your distance from your array to the charge controller?


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## jjh81 (Aug 17, 2010)

Im shooting for no more than about 30 ft my inverter needs to be within about 15 ft of my electric panel


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## Murby (May 24, 2016)

jjh81 said:


> Im shooting for no more than about 30 ft my inverter needs to be within about 15 ft of my electric panel


What inverter are you using? Got a model number? 

It is important that your inverter is close to the battery bank, not the household 120/240 breaker panel. Once you convert the power to AC current, distances are no longer very important. Its the DC side that is critical.


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## jjh81 (Aug 17, 2010)

Murby said:


> What inverter are you using? Got a model number?
> 
> It is important that your inverter is close to the battery bank, not the household 120/240 breaker panel. Once you convert the power to AC current, distances are no longer very important. Its the DC side that is critical.


GPISW3000 its a go power best for what I could afford at the time wanted a Schneider but wasn't happening. Also Looking at the 6x6 diagram does that mean I only need to go to one breaker on my combiner box?


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## Murby (May 24, 2016)

jjh81 said:


> GPISW3000 its a go power best for what I could afford at the time wanted a Schneider but wasn't happening. Also Looking at the 6x6 diagram does that mean I only need to go to one breaker on my combiner box?


Go Power inverters are a mid level inverter.. I have two of them myself as backups, a 600 watt and a 2000 watt unit. They are among the best of the mid level units and find homes in boats and RV's as well as smaller off grid setups. You made a good choice going with Go Power and I don't think you'll regret it. 

That said, it is not important to have your inverter close to your household breaker box but it is important that the inverter is close to the batteries. For your 3000 watt inverter, you're going to want to use some 1/0 or 2/0 battery cable for connecting the inverter to the batteries. Yes, you could get away with less, but you don't want to.. use the bigger wire and the inverter will be your friend for it. 

You should be able to get away with a single breaker on your combiner box.. better to put one on each series string but I probably wouldn't bother with that myself considering the small size. Extra breakers add extra levels of protection but one must draw the line somewhere right? 

Just make sure your using standard 10ga PV wire on your array, even if there was a short circuit to ground, the individual strings of 4.8 amps would not be capable of damaging a 30 amp wire.


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## jjh81 (Aug 17, 2010)

I have 6 breakers in my box so I figure if I use three what harm could it be. How far do you think I can run wire for the inverter to house? Also I do have 1/0 for my batt cables about a 2ft run from the breaker to the batteries


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## Murby (May 24, 2016)

jjh81 said:


> I have 6 breakers in my box so I figure if I use three what harm could it be. How far do you think I can run wire for the inverter to house? Also I do have 1/0 for my batt cables about a 2ft run from the breaker to the batteries


If you already have the equipment, use it all.. 

Inverter to the house? I would have thought the inverter was in the house.. How far do you need to go with it? Are you saying your batteries are outside? What kind of batteries?


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## wy_white_wolf (Oct 14, 2004)

Something I think you may have overlooked.

75 watts * 36 panels / 24 volts = 112.5 amps

The midnite classic 200 has an output limit of 78 amps at 24v. While I don't see what the input limit is for the charge controller, 800+ watts is a lot of power for the controller to burn up. I'd suggest you go with a six in series and only 4 strings until you can get a second charge controller or change to a 48 volt system.

WWW


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## jjh81 (Aug 17, 2010)

Murby said:


> If you already have the equipment, use it all..
> 
> Inverter to the house? I would have thought the inverter was in the house.. How far do you need to go with it? Are you saying your batteries are outside? What kind of batteries?


No the inverter is not in the house the building dept where I am will not let me put it or batteries in the house. I need to go about 15 feet from my solar shed to the electric panel in the house.


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## Murby (May 24, 2016)

wy_white_wolf said:


> Something I think you may have overlooked.
> 
> 75 watts * 36 panels / 24 volts = 112.5 amps
> 
> ...


Nice catch.. I didn't see that in the specs


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## jjh81 (Aug 17, 2010)

Yeah looks like I'm going to have to run the 6x4 and I will be upgrading around the first of the year to the Schneider 48 volt inverter


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## Bearfootfarm (Jul 13, 2006)

jjh81 said:


> No the inverter is not in the house the building dept where I am will not let me put it or batteries in the house.


If it gets very cold where you are and the building isn't heated, you may want to do something about that before Winter.

And get something to remove snow from the panels.


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## Bearfootfarm (Jul 13, 2006)

jjh81 said:


> No the inverter is not in the house the building dept where I am will not let me put it or batteries in the house.


If it gets very cold where you are and the building isn't heated, you may want to do something about that before Winter.

And get something to remove snow from the panels.


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## Murby (May 24, 2016)

jjh81 said:


> Yeah looks like I'm going to have to run the 6x4 and I will be upgrading around the first of the year to the Schneider 48 volt inverter


 When I was doing research to purchase mine, I did a lot of reading and found that the older Schneider inverters had a good reputation, but something changed with the company and problems surfaced. One thing that really turned me off was a lot of customers saying their customer support is lousy. Its not something I can confirm because I didn't go with the Schneider.

Don't get me wrong, I'm not suggesting the Schneider Conext is low quality or anything, Schneider is well known in the electrical industry, its just that from what I was reading, most prefer the Outback Radian inverters over the Conext.

The Conext units have some advantages over the Outback units but most folks say the Outback is more robust. Heck, just compare the weights of the two brands, the Outback Radians are 25% heavier than the Conext.. I think that says a lot.

I liked the Conext units, but in the end, I went with the Radian 8048.. I've always heard a lot of good things about Outback equipment and decided to stick with them. From what I could surmise, the SMA SunnyBoy products are the best for grid tie and the OutBack for off grid.


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## jjh81 (Aug 17, 2010)

Murby said:


> When I was doing research to purchase mine, I did a lot of reading and found that the older Schneider inverters had a good reputation, but something changed with the company and problems surfaced. One thing that really turned me off was a lot of customers saying their customer support is lousy. Its not something I can confirm because I didn't go with the Schneider.
> 
> Don't get me wrong, I'm not suggesting the Schneider Conext is low quality or anything, Schneider is well known in the electrical industry, its just that from what I was reading, most prefer the Outback Radian inverters over the Conext.
> 
> ...


I wish I could afford the radian but its about 2k more than my budget as I need to add AC to my place too maybe I can find something comparable or I will have to stick with the Schnider.


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## Murby (May 24, 2016)

jjh81 said:


> I wish I could afford the radian but its about 2k more than my budget as I need to add AC to my place too maybe I can find something comparable or I will have to stick with the Schnider.


One thing you want to make sure of is that the Conext can accept a dirty generator input. A lot of inverters out there with aux generator inputs can only accept generators that put out clean and stable power.. which most residential consumer style generators can not do. I know mine certainly doesn't. 

I know it was an issue when I was doing the research and one of the reasons I went with the Radian.. the Radian is designed to take dirty generator inputs. Voltage a bit too high or too low, frequency off a bit, bogging down on loading, all seem to have negative effects that some inverter/chargers can't handle.

You should call them and ask about that and find the documentation for it. Worst thing you can do is spend several thousand dollars with plans and expectations that don't get met.


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## jjh81 (Aug 17, 2010)

Murby said:


> One thing you want to make sure of is that the Conext can accept a dirty generator input. A lot of inverters out there with aux generator inputs can only accept generators that put out clean and stable power.. which most residential consumer style generators can not do. I know mine certainly doesn't.
> 
> I know it was an issue when I was doing the research and one of the reasons I went with the Radian.. the Radian is designed to take dirty generator inputs. Voltage a bit too high or too low, frequency off a bit, bogging down on loading, all seem to have negative effects that some inverter/chargers can't handle.
> 
> You should call them and ask about that and find the documentation for it. Worst thing you can do is spend several thousand dollars with plans and expectations that don't get met.


Do you know if I need to use there whole setup or if I just use the Inverter? Don't want to have to replace my whole setup.


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