What size wire do you need for insulation? Can you use an aluminum wire or does it have to be copper?

For the R4H436GKC's 30 Amp double pole circuit and the FEM4X3600BL's 15 Amp double pole circuit, I would recommend using 10 gauge copper wire for both. If you are also adding an electric heat strip kit, you will need to factor that in as well for the air handler's wire size and breakers.

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