Motor conductor sizing

[Alwayslearningelec]

Reading and article and it stated this ….

For motors marked with design letters B, C, or D, you can use conductors having an insulation rating of 75°C or higher if the ampacity of such conductors doesn’t exceed the 75°C ampacity listed in Table 310.15(B)(16) [110.14(C)(1)(a)(4)].

..does this mean that no matter what , if terminals are 90 degree or if using correction factors etc., basically anything that would allow you to use the 90 degree column you CAN’T?

Also, it stated this…

For equipment rated 100A or less, you must size the conductors using the 60°C temperature column of Table 310.15(B)(16) [110.14(C)(1)(a)(2)].

…are there exceptions to this where you can use the 75 or 90 degree column? Id have to imagine so as a lot of the loads we use when sizing are under 100a and we rarely use the 60 degree column .

 

[infinity]

For equipment rated 100A or less, you must size the conductors using the 60°C temperature column of Table 310.15(B)(16) [110.14(C)(1)(a)(2)].

…are there exceptions to this where you can use the 75 or 90 degree column? Id have to imagine so as a lot of the loads we use when sizing are under 100a and we rarely use the 60 degree column .

If the terminations are rated for 75° C then you can use the 75° C ampacity from the table. This is why the 75° C ampacity is almost always used (NM cable being an exception).

For all intents and purposes with the exception of adjustment factors (derating) forget that the 90° C ampacity even exists.

 

[augie47]

"For motors marked with design letters B, C, or D, you can use conductors having an insulation rating of 75°C or higher if the ampacity of such conductors doesn’t exceed the 75°C ampacity listed in Table 310.15(B)(16) [110.14(C)(1)(a)(4)]."

If that's the exact wording of the Article I think it would be be best to ignore the article
Go by infinity's guideline and the wording in 110.14

 

[infinity]

I tell my apprentices that in 2022 you can use the 75°C column for just about everything with the exception of NM cable. That will guide you correctly in 99% of all installations.

 

[wwhitney]

I tell my apprentices that in 2022 you can use the 75°C column for just about everything with the exception of NM cable.

We've had this discussion before, but LFNC and LFMC in wet conditions are also exceptions.

Cheers, Wayne

 

[Alwayslearningelec]

I tell my apprentices that in 2022 you can use the 75°C column for just about everything with the exception of NM cable. That will guide you correctly in 99% of all installations.

What column is used for NM cable? And by NM cable romex is obvious but also SER cable is obviously considered NM cable correct?

 

[infinity]

What column is used for NM cable? And by NM cable romex is obvious but also SER cable is obviously considered NM cable correct?

NM cable must be used with 60° C column. SE cable has 17 different rules depending on what code cycle you're on. As I said for us 99% of the time we just use 75° C because we don't use NM cable in commercial work. The other 1% will cover the things that Wayne mentioned and similar items.

 

[don_resqcapt19]

What column is used for NM cable? And by NM cable romex is obvious but also SER cable is obviously considered NM cable correct?

No. It is a completely different cable and has its own article and own product standard.