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Old 01-26-2016, 12:19 AM   #81
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Thank you, Lew and Alano. There is so much to learn.
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Old 01-26-2016, 12:28 AM   #82
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The Wynns are sponsored and not technical people. Just watch Jason's video on installing a composting toilet. They just have really good production value because that's what they do professionally. And that create the air of authority.

But they're not the only ones who are trying to sell something.
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Old 01-26-2016, 05:38 AM   #83
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Our GS-100 solar panels are sold as having a 5.5 amp output so five of them (like on our 23D) are capable of a 27.5 amp current which exceeds the continuous load rating of #10 wire which is 24 amps per the National Electric Code. On our Classic with nine of the same panels, they current generated would approach 49.5 amps which greatly exceeds the 30 amp maximum current rating of #10 wire.

The TriStar 60 MPPT remote display has shown 600 watts coming off the existing eight solar panels, Dividing by the nominal 12.5 VDC means 48 amps of current. Dividing by 18 Vdc would be 33.3 amps. So #10 wire lacks the amperage capacity for our installation before even considering voltage drop.
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Old 01-26-2016, 09:03 AM   #84
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I still have my GS print out I got with my latest panel. My GS-135 is rated at 7.71 IMP and the GS-100 is rated at 5.7 IMP. So 7.71 amps *3 = 23.13amps + 5.70amps =28.83amps.

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1. 10 AWG wire can quite easily handle the 960 W series connected array with low loss. Let's say the output voltage is 100 V, then the current is 960W/100V = 9.6A. If we assume the 10 AWG wire pair runs 75/2 feet, then the total wire length is 75', and the losses are 75'/1000'/millohm = .075 ohm. At 9.6A the voltage drop is 0.72V. So the voltage loss due to the 10 AWG wires represents a loss of 0.72/100 = 0.72%. Not too shabby!
I'm not sure how you arrived at this. If I use the Vpm rating of my panels and do 17.5 * 4 I get 70 volts. Following your math example

500W/70V = 7.14A - Pretty sure my system is putting out more than 7.14 amps.

Once upon a time. I use this as my handy guide for wiring.
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Old 01-26-2016, 10:16 AM   #85
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Originally Posted by switz View Post
Our GS-100 solar panels are sold as having a 5.5 amp output so five of them (like on our 23D) are capable of a 27.5 amp current which exceeds the continuous load rating of #10 wire which is 24 amps per the National Electric Code. On our Classic with nine of the same panels, they current generated would approach 49.5 amps which greatly exceeds the 30 amp maximum current rating of #10 wire.

The TriStar 60 MPPT remote display has shown 600 watts coming off the existing eight solar panels, Dividing by the nominal 12.5 VDC means 48 amps of current. Dividing by 18 Vdc would be 33.3 amps. So #10 wire lacks the amperage capacity for our installation before even considering voltage drop.
Let's forget for a moment that there's something called a MPPT solar charger in between the panels and the batteries. So in switz's case, he has connected all his panels in parallel, so yes the currents add for each panel in parallel. On his 23D the current from his panels is 27.5 A and I wouldn't recommend using 10 AWG wire because of the resistive losses. However, when you connect panels in series the current remains the same but you keep increasing the voltage, just like you do when you connect batteries in series. So in Wynn's case, they've connected 6 panels in series. Therefore the current remains the same, 9.6A, but the voltage is nearly 100 V. The total power is V*I = 100V * 9.6A = 960W.

Now the output of the panels is connected to a MPPT charger. This is actually a sophisticated DC/DC charger which in this case takes a higher DC voltage and converts it to a lower DC voltage with high efficiency among other nifty things I won't go into here. In Wynn's case the 960W at 100 V is converted to 960W at 13.7 V (just as an example), so at 13.7V the Wynns have 960W/13.7V = 70A of charging current available to the batteries if we assume that the MPPT charger has 100% efficiency. Typical efficiencies run in the range of 92% to 97%.

In Bold's example, IF he mounted his 4 panels in series, then yes, the total voltage would be 70V and the current would be 7.14A. If he connected this to a MPPT controller that can accept 70V, then the controller would deliver 70V*7.14A = 500W to the input of the MPPT controller and the controller would supply 500W/13.7V = 36.5A when charging the batteries, assuming 100% efficiency. I'd have to check with Bold but I'm pretty sure he did not connect his panels in series. This isn't a problem, it just means that the current from his solar array is 4*7.14A = 28.5A and therefore he had to use wire larger than #10 AWG to carry the current.

In my own installation, I connected my 4 100W panels in a series/parallel configuration and I'm able to reuse the existing solar pre-wiring while keeping the voltage losses due to the pre-wiring at less than 2%.
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Old 01-26-2016, 12:44 PM   #86
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Mine are in Parallel because I was worried about shading when we get back to the Pacific North West this year.

Thanks for the explainer, that makes a lot of sense and I totally didn't even think/realize the parallel/series exception with the panels. That's good information to know.
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