How Many Amps Can a Wire Carry? Conductor Ampacity Basics

In this video, we cover compressor ampacity basics and answer the common question: how many amps can a particular wire type carry? We also explain where people can look to find out more information.

You can look up the National Electrical Code (NEC) for free to search for wire and conductor ratings. The NEC has tables with wire ratings, including 310.15(B)(16).

Table 310.15(B)(16) gives you temperature and ampacity (size) ratings for different conductors. For example, number 10 wire at a 140-degree-Fahrenheit insulation rating is rated for 30 amps. However, when you have a 167-degree-Fahrenheit insulation rating with copper conductors, it's rated for 35 amps.

We sometimes use non-metallic cable, which generally has a 140-degree-Fahrenheit insulation rating, so that's why we say that number-10 wire can carry 30 amps.

However, there are certain types of wires and assemblies that have specific application concerns, and they may not be able to go into damp environments. Overall, we have to understand that ratings are NOT always what they seem; we have to look at applications and derating factors to make sure we're using the correct wiring.

Read all the tech tips, take the quizzes

[neppy]

glad i found this video, helps to explain the different wire size recommendations i was getting from different online wire size calculators given the same inputs

[kennethbaker]

Also depends on the terminal (breaker, etc.) you are landing it on. Most are rated at 75 Degrees. so you have to use the 75 Degree column.

[MrKeith]

I absolutely love when people teach on here that have no idea what they’re talking about. Table 310.15 is one of the most confusing parts of the NEC. That was explained 100% incorrect

[ladjkaoz]

good info, but im a lil slow...
IF 10 gauge can do up to 30 amps Black Neutral Ground 120V, but if you I do 240V Hot Hot Ground it would drop to 15Aright? I'm a mobil DJ I have 2 amplifiers that draw about 22A at 120V I usually wire them to a 120V 20A circuits but the lights of the buildings dim which the music... I just got this idea pluging a 10/2 (B hot, W hot, G ground) cord to the panel. when I run then one the 120V 20A I have to keep them below their max power and monitor the current draw so the breakers won trip till. Also I have other gear Wish Incould connect to this 10/2 cord but don't want to have fireworks... if you know what I mean...😉

[helpyfanvlogs]

Hi, Do you know what gauge I have to use to power up 20 amp light? The light is 35 feet away from main source, thanks

[spelunkerd]

As a Canadian, I find this topic very confusing. The prevalent nonmetallic cable here is NMD90, good to 90 deg C. Terminal connections are the bottleneck, where breakers are limited to 60 or sometimes 75. If any part of the circuit is limited to 60, the whole circuit is derated.

[benjaminvandenberghe]

Dang what's that piano riff at the beginning of the video?

[jinshikami]

Ohm my gosh you should try this application! Observe: androidcircuitsolver/app.html

[jimmyjohnson]

Why not talk the basics All this number letter stuff wont wire anything for me ! Not looking to transport do want electicity to my garage ! Nothing explain about wire carrying capacity or different types of wire !

[orlandojohnson]

All I wanted to know was the amperage usually used for 30 amps or 60 amps!
I know 10 awg gauge is used for average length for 30 amps!
What's 8 gauge & what's 6 gauge used for!?
8 gauge good for 60 amps!? Or do you use 6?!

I had a chart! Can't find it!
I don't need a narrator!
Lol 😂🙄

[neppy]

glad i found this video, helps to explain the different wire size recommendations i was getting from different online wire size calculators given the same inputs