Quick Hits

⚡ NEC Quick Hit: Conductor Properties & DC Resistance (Table 8) ⚡

Doing voltage drop calculations? You live and die by Chapter 9 Table 8. Let's break down DC resistance at $75^\circ\text{C}$ for copper and aluminum conductors from #14 up to heavy feeders! 👇

SLIDE 2 (COMMON BUILDING WIRE SIZES: #14 to #2)

DC Resistance ($\Omega$ per 1,000 ft at $75^\circ\text{C}$):

• #14 Solid Copper: 3.07 $\Omega$ / kFT (Aluminum: 5.06)

• #12 Solid Copper: 1.93 $\Omega$ / kFT (Aluminum: 3.18)

• #10 Solid Copper: 1.21 $\Omega$ / kFT (Aluminum: 2.00)

• #8 Stranded Copper: 0.778 $\Omega$ / kFT (Aluminum: 1.28)

• #2 Stranded Copper: 0.194 $\Omega$ / kFT (Aluminum: 0.319)

SLIDE 3 (HEAVY FEEDER SIZES: 1/0 to 500 kcmil)

Feeder DC Resistance ($\Omega$ per 1,000 ft at $75^\circ\text{C}$):

• 1/0 Stranded Copper: 0.122 $\Omega$ / kFT (Aluminum: 0.201)

• 4/0 Stranded Copper: 0.0608 $\Omega$ / kFT (Aluminum: 0.100)

• 250 kcmil Copper: 0.0515 $\Omega$ / kFT (Aluminum: 0.0847)

• 500 kcmil Copper: 0.0258 $\Omega$ / kFT (Aluminum: 0.0424)

SLIDE 4 (FIELD TAKEAWAY & WRAP-UP)

💡 Apprentice Pro-Tip: Notice how aluminum resistance is consistently higher than copper for the same gauge size? That's why aluminum conductors generally require a size bump up when you're calculating long runs and mitigating voltage drop!

💬 Save this post for your next voltage drop exam question or field calculation!

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