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Solar wire gauge - how many amps

solar wiring amps

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#1 Helmut

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Posted 21 September 2019 - 02:53 PM

Hi to all,

 

I have a 2017 Grandby with the ZAMP 160W panel (factory installed). I extended it with two flexible 120W panels and ev was fine for about 1and1/2 years. Then one of the flexible panels failed and shortly after that the other. The max amps I had seen on the ZAMP charge controller display was 17amp. Now I am thinking of replacing the two faulty panels with another rigid one and remember stumbling over a post somewhere that the capacity of the solar wiring is limited. So I checked with FWC and aws told the system is limited to 200watts. ??????? That seems awful low to me as I read a lot of post of larger solar systems and don`t have the impresssion that everybody switched from the ZAMP PWM controller to a MPPT type and connect the panels in series instead of parallel.

Is there any expierience/knowledge out there how many amps I can safely run through my FWC solar wiring?

 

thanks for input

 

Helmut

 


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#2 rando

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Posted 21 September 2019 - 04:07 PM

There is a lot of confusion and misinformation on this question.   

 

The definitive answer is that you can run currents up to the carrying capacity of the wire:

Ampacity-Table.png

Source: https://shop.pkys.co...ables_b_43.html

 

My understanding is that FWC uses 12AWG wire for their solar systems (but you should check your wiring), which means you could safely use up to 750W (45A * ~17V) of solar with the stock wiring and the panels in parallel.   Realistically you couldn't fit or lift that much solar on the roof, so the wiring is not a limiting factor.      


Edited by rando, 21 September 2019 - 04:09 PM.

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#3 Helmut

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Posted 21 September 2019 - 04:18 PM

thanks Rando,

 

that does calms me down. FWC told me they use 10AWG, but whatever I don`t have to worry.

 

different question - similar problem: The wires running from the IOTA charger to the batteries seem very thin and long. Wouldn`t the batteries charge a lot faster with the IOTA as close as possible and connected with heavy wires to the batteries?

 

thanks in advance again ( bet you can give me a good advice )

 

Helmut


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#4 rando

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Posted 21 September 2019 - 04:50 PM

Battery charging is very sensitive to voltage drop - so yes shorter, fatter wires between the IOTA and the battery should help.  


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#5 ClimberRob

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Posted 21 September 2019 - 04:50 PM

Good info from Rando above. Here's an easy-to-use chart, as well: https://www.westmari...ze-And-Ampacity

 

The wiring on my stock IOTA charger were severely undersized (in addition to the fact that my IOTA charger was never even wired up at the factory- oops!). You can use the West Marine chart above to figure out what size wire would be ideal and compare to what you have installed currently.


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#6 Helmut

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Posted 21 September 2019 - 05:10 PM

thanks, getting a little smarter again :)


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#7 rando

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Posted 21 September 2019 - 06:38 PM

Good info from Rando above. Here's an easy-to-use chart, as well: https://www.westmari...ze-And-Ampacity

 

The wiring on my stock IOTA charger were severely undersized (in addition to the fact that my IOTA charger was never even wired up at the factory- oops!). You can use the West Marine chart above to figure out what size wire would be ideal and compare to what you have installed currently.

 

Just be sure to refer to the last chart in that link ('AWG Wire Specs') for solar panel wiring.   Much of the confusion on this seems to come from applying 3% or 10% voltage drop limit (first two charts) to solar wiring, leading to suggestions for massively oversized wire.


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#8 Jack

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Posted 21 September 2019 - 09:45 PM

Voltage drop depends on distance and current. The shorter the distance and/or the lower the current, the less drop in voltage for the same gauge wire. Rando's link to the West Marine chart tells you what you need to know. Note that the critical voltage levels for AGM batteries occurs when they are nearly charged, at which point the current is much less and the voltage drop decreases substantially. The same issue exists when charging off your truck's alternator.


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