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 |
|---|---|---|---|---|---|---|
 |
Two, Copper | NM-B 14/2 | 14/2 | 14 solid | Solid | 15 amps @ 75 celsius |
 |
Three, copper | NM-B 14/3 | 14/3 | 14 solid | Solid | 15 amps @ 75 celsius |
 |
Two, Copper | NM-B 12/2 | 12/2 | 12 solid | Solid | 20 amps @ 75 celsius |
 |
Three, copper | NM-B 12/3 | 12/3 | 12 solid | Solid | 20 amps @ 75 celsius |
 |
Two, Copper | NM-B 10/2 | 10/2 | 10 solid | Solid | 30 amps @ 75 celsius |
 |
Three, copper | NM-B 10/3 | 10/3 | 10 solid | Solid | 30 amps @ 75 celsius |
 |
Three, copper | NM-B 8/3 | 8/3 | 10 solid | 7 strands | 40 amps @ 75 celsius |
 |
Three, copper | NM-B 6/3 | 6/3 | 10 solid | 7 strands | 55 amps @ 75 celsius |
 |
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!
