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Indoor Electric Cable Types

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I am about to install a portable generator hookup and since it is reeeally important to properly size my cable between the inlet box and my main load center, I thought I share what I found out.

Although I use the term “Romex” (brand owned by Southwire) you can certainly use other brand with same specs (i.e. Cirtex made by CirroWire).

Image # of Conductors Cable Type AWG Size Ground Stranding Ampacity
romex-nm-b-14-2-fl Two, Copper NM-B 14/2 14/2 14 solid Solid 15 amps @ 75 celsius
romex-nm-b-14-3-fl Three, copper NM-B 14/3 14/3 14 solid Solid 15 amps @ 75 celsius
romex-nm-b-12-2-fl Two, Copper NM-B 12/2 12/2 12 solid Solid 20 amps @ 75 celsius
romex-nm-b-12-3-fl Three, copper NM-B 12/3 12/3 12 solid Solid 20 amps @ 75 celsius
romex-nm-b-10-2-fl Two, Copper NM-B 10/2 10/2 10 solid Solid 30 amps @ 75 celsius
romex-nm-b-10-3-fl Three, copper NM-B 10/3 10/3 10 solid Solid 30 amps @ 75 celsius
romex-nm-b-8-3-fl Three, copper NM-B 8/3 8/3 10 solid 7 strands 40 amps @ 75 celsius
romex-nm-b-6-3-fl Three, copper NM-B 6/3 6/3 10 solid 7 strands 55 amps @ 75 celsius
romex-nm-b-4-3-fl Three, copper NM-B 4/3 4/3 8 strands 7 strands 70 amps @ 75 celsius
TIP: A quick way to tell a difference between a 15 amp (14 awg) wire vs 20 amp (12 awg) wire is to compare the thickness. 14 awg resembles the width of a dime, 12 awg resembes the width of a nickle

Quick Size and AMP Ratings (NM, TW & UF WIRE)

  • 14 AWG – 15 AMPS
  • 12 AWG – 20 AMPS
  • 10 AWG – 30 AMPS
  • 8 AWG – 40 AMPS
  • 6 AWG – 65 AMPS

Quick Size and AMP Ratings (SERVICE CABLE)

  • 8 AWG – 50 AMPS
  • 6 AWG – 65 AMPS
  • 4 AWG – 100 AMPS
  • 2 AWG – 125 AMPS
  • 1 AWG – 150 AMPS

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Thanks and good luck with your DIY project!

 

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