[Conflict]

Born and raised in central FL. Recently moved to upstate SC. Taking classes in residential and commercial wiring. I am terribly confused by the wording differences between 110.14C1a2 and 110.14C1b2; "ampacity is determined based on" versus "ampacity does not exceed", respectively. Has that been discussed? Should that be a new thread? Obviously it is significant or they would have worded it the same way. Under 100 amps, 55 amp conductor is fine for 40 amp load. Over 100 amps 170 amp capable conductor is no good for a 150 amp load because it exceeds "the 75C ampacity" of the conductor? How does that make sense?

 

[HARRY304E]

Born and raised in central FL. Recently moved to upstate SC. Taking classes in residential and commercial wiring. I am terribly confused by the wording differences between 110.14C1a2 and 110.14C1b2; "ampacity is determined based on" versus "ampacity does not exceed", respectively. Has that been discussed? Should that be a new thread? Obviously it is significant or they would have worded it the same way. Under 100 amps, 55 amp conductor is fine for 40 amp load. Over 100 amps 170 amp capable conductor is no good for a 150 amp load because it exceeds "the 75C ampacity" of the conductor? How does that make sense?

Hello welcome aboard.:thumbsup:

What year code book are you reading?

 

[Conflict]

2014. But I think 2011 is worded the same. My class up at the local technical college can't make sense of it either.

 

[HARRY304E]

2014. But I think 2011 is worded the same. My class up at the local technical college can't make sense of it either.

They're taking about table 310.15(B)(16)

Look at the table columns, you have,

60c 75c and 90c temperature.

In each column has the ampacity of the conductor

The temperature ratings of your terminals will be marked with that temperature rating,lets say it's 75c 1/0 copper is good for 150 amps in the 75c collumn,you cannot go above 150 amps with that size wire under your 75c rated lug because it will over heat.

As you can see 1/0 is good for 170 amps at 90c but your lugs must be rated for 90c too.

 

[HARRY304E]

2014. But I think 2011 is worded the same. My class up at the local technical college can't make sense of it either.

You're right about the wording it's screwy..:laughing:

 

[guest]

Moved to the NEC Forum to get better answers to the OP's questions.

 

[HARRY304E]

Moved to the NEC Forum to get better answers to the OP's questions.

Good man..:thumbsup:

 

[Conflict]

lets say it's 75c 1/0 copper is good for 150 amps in the 75c column,you cannot go above 150 amps with that size wire under your 75c rated lug because it will over heat.

So my question is, does that also apply under 100 amps? Because under 100 the code only says based on, instead of shall not exceed. Thanks for the response.

 

[NacBooster29]

You can always run a larger cable than load requires.

 

[HARRY304E]

So my question is, does that also apply under 100 amps? Because under 100 the code only says based on, instead of shall not exceed. Thanks for the response.

Yes it does.