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add 6mm to 4 mm cable from pv array to inverter ?

gramos100

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Aug 24, 2020
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Can I ask for some advice please , I am installing my Rosen Solar off grid system .

I have 4 x strings of 7 x 400 w panels into a combiner box , and have 2x Growatt 5k inverters which involves a 36 metre cable run .
I have 100M rolls of cable 1x black , 1x red to carry the power , according to various calculators the 4mm has not sufficient capacity .
So as I can utilise my cable and add another cable , 6mm to increase the capacity , giving a total of 10mm .

Is this a sound idea ?
is my logic applicable ?


many thanks ,
Graham , Greece
 
IMHO if you’re “adding cable” ie a second conductor to facilitate better voltage drop characteristics I would simply return or sell the 4mm and buy the cable size required for the application.
 
How much volts are each string? At 250v, you’re around 45A, and I’d recommend 16mm2 for that load over any appreciable distance… adding 6, would help the issue, but replacing it with 16 is far better.
 
IMHO if you’re “adding cable” ie a second conductor to facilitate better voltage drop characteristics I would simply return or sell the 4mm and buy the cable size required for the application.
Thanks but it's not worth posting back to China 2 X 100 M reels of cable and then paying import duties when the bigger cables are sent.
 
How much volts are each string? At 250v, you’re around 45A, and I’d recommend 16mm2 for that load over any appreciable distance… adding 6, would help the issue, but replacing it with 16 is far better.
Thank you , I checked the output on each string today and it varies between 306 and 362 ,I am trying to keep down extra costs by adding more cable to the 4 mm as the reels are already bought from China
 
How much volts are each string? At 250v, you’re around 45A, and I’d recommend 16mm2 for that load over any appreciable distance… adding 6, would help the issue, but replacing it with 16 is far better.
Hi , Thanks for your reply , I saw youre in NC my niece just bought a house in Lenoir ! We flew into Charlotte for the wedding .

I have a 36 metre run and have enough red and black 4 mm for 2x runs each so total , my cable ,
is 8mm so with the 10mm I can get here makes 18mm
Do you think this s enough ?
 
Hi , Thanks for your reply , I saw youre in NC my niece just bought a house in Lenoir ! We flew into Charlotte for the wedding .

I have a 36 metre run and have enough red and black 4 mm for 2x runs each so total , my cable ,
is 8mm so with the 10mm I can get here makes 18mm
Do you think this s enough ?
 
Lenoir is beautiful, and high up away from the humidity we get pounded with… lucky.

So, you are considering three cables in parallel. It really isn’t recommended. Lengths need to be EXACT, and each run needs fusing, and fire or connection issues are common… and fusing introduces additional resistance issues.
A single 16mm is far safer.
 
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