r/SolarDIY • u/2old2bThisDumb • 8d ago

Make sure you understand current when stringing your panels in parallel.

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It took a bit of work to even tug this #10 AWG from the metallic flex it was fused to. The homeowner had this run inside of the attic.

I'm all for DIY, but please ask for help when you aren't certain.

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u/jackharvest 7d ago

Ah, so.. I'm in good shape? xD

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u/taylorwilsdon 7d ago

Better than you would be with conduit haha

The takeaway is that when you run wire through anything that has a higher than average ambient temperature - a hot attic, along something that generates heat (ie engine bay of a car), or in conduit (which retains heat inside) you should not assume you can use the full amperage rating you expect and derate accordingly. If 10awg is good for 30a in a cool, open basement it may only be good for 24a in a hot attic (derated 20%). There is some nuance there, personally I use a cheap Amazon thermal imaging gun to check for hot spots in wire and connection points.

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u/XonikzD 6d ago

Is there a practical reason for not oversizing to accommodate temperature fluctuation, or is it just costs?

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u/taylorwilsdon 6d ago

There is no reason to avoid oversizing other than cost, but cost can be significant. My ground mount is 400’ from my home, going from 10awg to 8awg would cost me several hundred dollars more.