studying for test

[teeg123]

I have a question on a practice exam and have not been able to grasp it.
The disconnecting means for a 50 HP, three-phase, 460 V induction motor shall have a minimum ampere rating of ?

1/ 60amps
2/ 100 amps
3/ 125 amps

So im in the 2023 nec I go to table 430.250 find my FLC of 65 amps
65amps X 1.15=74.75
for some reason be it a brain crap or what I cant seem to the answer they want of 100 amps
table 430.52 does my no good. I feel like im just missing something silly and will kick myself in the arse for it. The induction part appears to my to be the thing im messing up.

thanks for any help or assistance

 

[blueheels2]

Well it can’t be 60. It could be either of the other 2 but only one of them is the minimum.

But I’m not sure that’s right.

 

[infinity]

Well 100 amps is greater than the 74.75 amps so will that work?

 

[teeg123]

the answer s given but no steps on how to achieve it. i do appreciate everyone's help.

 

[teeg123]

Rob, yes 100 amps is the answer, but I don't imagine that they are rounding up to 110 from 74.75. I very well could be wrong.

 

[infinity]

Rob, yes 100 amps is the answer, but I don't imagine that they are rounding up to 110 from 74.75. I very well could be wrong.

Well the short answer is 74.75 is greater than 60 amps so 1) cannot be the answer. You're then left with two choices 100 and 125 amps, both are greater than 74.75 so it could be either 100 or 125 amps. Since they've asked for the minimum size and since either 100 or 125 would be code compliant the minimum would be the smaller of the two or 100 amps.

 

[teeg123]

thanks again