Sizing a industrial Machine

[jggramlin]

First sizing a machine like this and only guy with electrical experience so looking for some extra brains.

Need to size fuses at disconnect and wire to the machine. Where it terminates to a 15amp theee pole fused disconnect in the control cabinet.

Name Plate:
FLA of largest motor: 6.7
3 phase
480v
FLA: 13.81

I went to 670.
Found 125% of largest motor plus sum of everything else. (No heating element)

So i did WOLF

Wire= FLCode x 1.25
7.6 (Motor Table) x 1.25 =9.5
9.5 +13.81 = 23.31
Going with 10 wire

670
OL = OverLoad
13.81 x 1.25= 17.26

F = fuse
FLC x 1.75 =
13.81 x 1.75= 24.1675
Round up and go

Just looking for advice or anything advice for tricks of the trade

 

[Barney B]

Most of your work is fine, but, your calculation for the fuses is incorrect.
For a multi-motor load, you must:
1. Size a fuse rating for the largest motor alone (in your case 7.6A x 175% = 13.3A = 15A fuse).
2. Add 100% of the remaining loads to this value (in your case 15A + 13.81A = 28.81A).
3. Since the value shown in the second step is a "not to exceed" limit, you must use the next lower standard rating (in your case 25A fuses).

Read NEC Article 430.62(A)

 

[retirede]

The way you present the nameplate data, I would expect the largest motor amps to be included in the machine FLA. is that not the case?

 

[jggramlin]

It gives me a FLA of the motor (there is only one) and the FLA of the entire machine. I would think the motors FLA would be included

 

[augie47]

Normally the nameplate FLA is all need need to take into account. Adding to that you state the machine has a 15 amp internal fusible disconnect so any feed 15 amps or above should be fine. I'd likely run a 20 amp circuit to it with #12s.