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Need help with wire gauge size

Joe Blow

New Member
Joined
Nov 13, 2022
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4
Hello everyone,

I am trying to construct a solar power system to bring some power to my shed. These are the basics of my system:

600W Solar panels
40A MPPT Solar Charge Controller
1500W Pure Sine Wave Inverter
2 x 100AH 12V LiFePO4 Batteries
Circuit Breaker & Fuses

I am having trouble figuring out the gauge of copper wire I will need to connect all the various components together. Can anyone offer some advice, or point me in the direction of a resource that can assist me?

Thank you in advance for your help. It is appreciated.

Regards,
Joe
 
Hello everyone,

I am trying to construct a solar power system to bring some power to my shed. These are the basics of my system:

600W Solar panels
40A MPPT Solar Charge Controller
1500W Pure Sine Wave Inverter
2 x 100AH 12V LiFePO4 Batteries
Circuit Breaker & Fuses

I am having trouble figuring out the gauge of copper wire I will need to connect all the various components together. Can anyone offer some advice, or point me in the direction of a resource that can assist me?

Thank you in advance for your help. It is appreciated.

Regards,
Joe
Here are a couple of resources:

1) This should help provide guidance on the wires to the panels. https://diysolarforum.com/resources/fusing-wire-sizing-guidelines-for-solar-panels.144/

2) This resource helps determine the minimum wire size between the battery and the inverter. (If the inverter manual says to use a larger wire, follow the manual)

3) When selecting the minimum wire size for a given current, the type of insulation is a big factor in determining the correct gauge. I use this chart when looking up wire size (But you need to know the temperature rating of the wire)

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Note: I typically use marine-rated wire with 90C temp rating. It is more expensive than other wires but it is very flexible and has good ampacities.

Note 2: Bigger wire is better (Less voltage drop) so I will often go one or two gauges larger than calculated unless it creates a physical problem such as not fitting into the components. For short runs, the extra cost is not that great. The longer runs are usually to the panels and the way NEC calculates wire size often ends up with a low voltage drop anyway. It only gets to be an expensive proposition on really long runs to the panels.
 
Once you come up with the wire sizing feel free to respond in this thread if you want help double checking. The last thing you want to do is buy a bunch of wire that ends up being unsafe, or not size protection adequately. Best of luck !
 
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