Fact check: Higher volts requires larger gauge wire

[timblack1]

The fellow behind the counter at a solar store gave me some good advice, but stated a few things on which I'd like to get a second opinion. Here's one: 8 AWG wire could handle 9.6 A over 40 feet if there were only 1-3 panels put in series (creating 37 - 111 V), but since I plan to put 7 panels in series, creating 260 V (but still no more than 9.6 A), I'd need a larger gauge wire.

Is that true? Or will 8 AWG wire handle the 260 V just fine, since the amps remain the same at 9.6 A? This wire, which I would consider using, states it is rated for 2000 V - https://www.amazon.com/WindyNation-...riety-Available/dp/B01L6OU74M/ref=as_li_ss_tl. I've been using this ampacity chart:

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[time2roll]

False. Possibly move down to more common #10 wire. With more voltage the percent of loss drops.
My home solar is 3 kW and uses #10 wire at up close to 450 volts with panels close to 80' from the inverter.

 

[MisterSandals]

Using your numbers, 8awg, 9amps, 40ft and comparing 111V vs 260V it shows that there is much lower voltage drop at 260V so I would have to say false, seemingly the opposite.

 

[rmaddy]

Some additional thoughts beyond your immediate question:

While current and voltage drop are main factors in choosing wire size, also keep in mind that you also need to make sure the chosen wire is rated for the voltage you will have. Good quality marine-grade copper wire can typically handle 600V so you don't really need to worry about the voltage. But if you cheap out on your wire, make sure it can handle the needed voltage.

Also understand the limits of your chosen solar charge controller. Panels in 7s with a Voc of 260V (more in colder weather) means you need a SCC that can handle that voltage. Some only handle 100V (or less), some 150, some 250, and a few can handle even more. Make sure yours can handle 300V or more if you go 7s with your panels.

 

[toms]

Please stop listening to that fellow behind the counter.

 

[curiouscarbon]

The “insulation” on your cables is just another conductor in disguise!

If the voltage going through the wire is high enough, the insulation sheath itself will conduct electricity and that is usually bad day.

Cables generally have a max voltage rating, and from what I’ve heard around, it’s based on 1) what metal for the conductor and 2) what material for the insulator and 3) how thick the insulation layer is

The wire I bought for my DIY solar stuff seems to all be rated for 600V, usually it’s written in a repeating text along the side of the wire.



This one says 15000 Volts on the Cable Jacket Information, so that’s gotta be some thick or very good insulation.

Anyways, for DC you can pretty much say one voltage rating for a given insulation thickness, I believe.. thick or thin cable conductor.

With AC, the voltage is changing so much that the outside of the wire has less “inertia” than the center so for AC the skin of the wire does the most work. So for AC thickness can matter more.

TL;DR for DC the size of the conductor is not what matters for voltage rating. it’s the thickness and type of insulator.

 

[12VoltInstalls]

for DC the size of the conductor is not what matters for voltage rating. it’s the thickness and type of insulator

not entirely true.

The presence- ability to measure- of voltage in/from a conductor is only a part of the factors to be considered. A tiny conductor can show/conduct 100 volts and not be able to pass the desired amperage.

I’m a little bit odd: I over-gage most low voltage wires. I’d also use 8ga for solar panel to controller LOL.

10ga will be fine- truth be told, I’ve only seen a measurable improvement difference (from over sizing wires) a small number of times. The only times I blindly say “this must be oversized to be acceptable!” is offroad vehicles and trailers with winches because, well, nothing oversized has caught fire!

I may not ‘blindly’ oversize battery to inverter cables. However, I always use ABYC for the surge amps. Then go up one size; if it calls for 1/0, I use 2/0 and fuse at the 1/0 amp rating. Yes it costs more- a lot more percentage-wise sometimes - but on the grand scale it’s usually only a pizza in dollars.

but ya, stop going to the solar store. What if they give you bad advice on something that leads to a house fire?

 

[kenryan]

Wires are rated for "ampacity" or how many amps they can conduct. Larger wires can conduct more amps.

Your solar panel generates a certain amount of power, which is rated in "watts."

Watts = Volts X Amps

So ...

If your panels generate 120 watts of power at a voltage of 12 volts, then the current would be 10 amps.

120 watts = 12 volts X 10 amps

If your panels generate 120 watts of power at a voltage of 120 volts, then the current would be 1 amp.

120 = 120 X 1

As you can see, as volts go up, wire size comes down (if all other things remain equal).

 

[timblack1]

This wire, which I would consider using, states it is rated for 2000 V - https://www.amazon.com/WindyNation-...riety-Available/dp/B01L6OU74M/ref=as_li_ss_tl.

Oops...I should have said it's rated for 600 volts, not 2000.

 

[timblack1]

Also understand the limits of your chosen solar charge controller. Panels in 7s with a Voc of 260V (more in colder weather) means you need a SCC that can handle that voltage. Some only handle 100V (or less), some 150, some 250, and a few can handle even more. Make sure yours can handle 300V or more if you go 7s with your panels.

Thank you. The manual at https://watts247.com/manuals/mpp/PIP-LVX/LVX6048 split phase manual-20210312.pdf?x65773, p. 28, says the LVX 6048's "Max. Input voltage (Maximum PV open voltage)" is 450 VDC. So I believe the 260 V the arrays I'm planning could produce should be far enough below the LVX 6048's max input voltage.