diy solar

diy solar

Southwire 10 AWG THWN Ok ?

Is this the type of wire most people are using for their solar panels to the combiner box?
My setup is 2P2S, 250w panels and looking to adding another 2P2S later on, or may go go 3P3S.
The run from panels to combiner box is about 50-70 feet.
https://www.lowes.com/pd/Southwire-...d-Black-Copper-THHN-Wire-By-the-Roll/50163633
Not for my RV. I use PV wire. That Lowe’s THWN wire is not for outdoor use. When I get that stuff at my local Lowes and Home Depot, the insulation is significantly thinner than PV wire.

I shop here forPV wire where it comes in black and red:

I now avoid thicker than 10 AWG wire by upping the voltage, but if I need a thicker wire than is available for PV, I use this:

Although PV wire is rated for outdoor exposure to the sun, I put the wire in split loom. I believe PV roof installations on houses need to be installed in conduit by code.
 
Great, thanks guys. I will certainly go with the PV wires instead of the THWN wire.

I was thinking of putting the combiner box about mid-way between the panels and the inverter/batteries. But I should put it close as possible to the panels, correct? To save on wire size?

Can I get away with 12 AWG wire from the panels to combiner box? Or should is10 AWG pretty much the standard for these MC connectors?
 
What’s the math of running 4 conductors longer to the combiner box vs one long run of two conductors from the box to your SCC?

What gauge will you use from the combiner box to the SCC?

Also a combiner box is a great way to include your over voltage protection device for the array which is best to keep it as close to the panels as possible.
 
I think whatever you end up with, the combiner box should be in an area easy to sure.

From good advice I got here, I changed my original plan of putting the combiner box on the hard to get to roof to the easy to use area next to my batteries. Made trouble shooting and posting the system on and off easy. I need to shut off the solar panels before removing battery power. I would have hated to climb to the roof each time to do it.

In my case I used 10 AWG from panels to the combiner box, and then 6 AWG from the combiner box To the SCC.

I first check ampacity to be sure the wire can handle the amps:


So no matter the volatage loss, for 10 AWG wire size I won’t use it more than 30 amps. Ampacity doesn’t care about length. Voltage loss does.

I then go to a website for a DC voltage loss calculator like this and try for less than 3% voltage loss with wire size and length:


Distance matters on voltage loss and will make a big difference.

I use 100 watt panels on two different strings and I use 175 watt panels to another SCC. Not quite 250 watt panels, but I’d do the same thing if I were calculating for 250 watt panels. I also built to be able to add panels on, which for the most part I have. The bigger combiner box I ran out of room for panels and can’t add on though.
 
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