Panel Schedule, phase load calculation

QUF

Member
Location
USA
Occupation
Student
How to calculate a Phase load on the Panel Schedule? Loads are 4x30hp motor and 2x 10hp

Panel board is 480v, 3p, 4w, 400A.



Thanks,
 

charlie b

Moderator
Staff member
Location
Seattle, WA
Look at NEC table 430.250, and find the current values for the motors. Use the 460V column. Multiply that value times 480 volts and again by the square root of 3 (about 1.732). That tells you the total KVA for the motor. Show one third of that value on each of the three phases. Do the same for the other 5 motors.
 

QUF

Member
Location
USA
Occupation
Student
Thank you sire,
I did that just to confirm,

40 (30hp)x 480x 1.7= 32640
32640 /3=
10880 pA
10880 pB
10880 PC

is that right ?
 

charlie b

Moderator
Staff member
Location
Seattle, WA
You have the right idea. I would suggest using a number that is closer to the actual square root of 3 than just 1.7. Even using 1.73 would get you a bit closer. The difference is just under 2%, so I would not make a big deal of it.
 
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