MI cable ampacity

[cppoly]

310.15(B)(17) - gives MI cable ampacity in free air but only gives ampacity using the 90 degree column. If you're going to size MI cable for fire pumps, don't you have to size it based on the 75 degree column as per 110.14(C) - so how do you get this ampacity if it's not listed in the chart?

 

[augie47]

MI is also listed in 310.15(B)(16), 90° Column./

 

[david luchini]

so how do you get this ampacity if it's not listed in the chart?

Move one column to the left.

 

[cppoly]

Move one column to the left.

Lol... well yea, but MI isn't listed in 75 degree column for some reason

 

[infinity]

Normal 90° C conductors (like THHN) aren't in the 75° C column either but they're sized at that ampacity all of the time.

 

[david luchini]

Lol... well yea, but MI isn't listed in 75 degree column for some reason

Neither is THHN. See 110.14(C).

Edit: Rob types faster than me.

 

[augie47]

As you noted in your original post. 110.14 would still apply so the "allowable" ampacity will be based on your termination devices.

 

[cppoly]

Thanks, that makes sense then