Motor question on terminal and wire sizing 60 degrees #8=40A, 75 degrees #8=50A, 90 degrees #10=40A?

[perl82480]

I was presented with a question I did not know how to answer, can someone please point me in the right direction please?

What is the minimum conductor size for a 10 HP motor 208v, 3 phase, using THHW-2. Type E

430.250 FLA IS 30.8A x1.25 per 430.22 = 38.5

Where I am getting confused, is when I’m in 310.15(B)(16) for sizing of the wires. They don’t call out a what the terminals are rated at so do you choose the

60 degrees #8=40A, 75 degrees #8=50A, 90 degrees #10=40A?

 

[don_resqcapt19]

I was presented with a question I did not know how to answer, can someone please point me in the right direction please?

What is the minimum conductor size for a 10 HP motor 208v, 3 phase, using THHW-2. Type E

430.250 FLA IS 30.8A x1.25 per 430.22 = 38.5

Where I am getting confused, is when I’m in 310.15(B)(16) for sizing of the wires. They don’t call out a what the terminals are rated at so do you choose the

60 degrees #8=40A, 75 degrees #8=50A, 90 degrees #10=40A?

For the supply end you will have to look at the equipment marking. Most currently available equipment will be marked for 75°C. However where the equipment is not marked, you have to use 60° for 100 amps or less. See 110.14(C)(1)(a)(4) for the motor end.

If this is a test question and not a real world question, the information for the test will often specify that for circuits 100 amps and less use the 60°C values.

 

[Jraef]

And for future reference, you almost never find terminations rated for 90C, so you can pretty much ignore that column. It's mostly only used when you are having to de-rate conductors for fill, temperature etc. and have conductor insulation rated for 90C.