Motor Wiring Questions

[Lectricbota]

I have (6)3 phase motors that I need to connect and am hoping someone will check my math.

Coming out of a panel with 2 circuits in 1" PVC conduit before branching off to feed 3 motors in both direction.

Circuit 1. (3) 5 hp motors.
Feeder Conductors. 16.7 FLC each so 125% of biggest+sum of others =54.275.
#6 THHN good for 65 amps(conductor bundling reduces to 60 amps-#6 still good).
Feeder Circuit Protection 250% of largest+sum of others=75.15 next size down=70

Circuit 2. (2)5 hp,and (1)3 hp motor.
Feeder Conductors.16.7,16.7, and 10.6 FLC. 125% of largest+sum of others=48.175.
#8 THHN good for 50 amps(conductor bundling reduces to 44 amps-need to increase to #6).
Feeder Circuit Protection 250% of largest+sum of others=69.05 next size down=60.

Branch Circuits for Motors.
#12 taps and branch conductors 5 hp motors with 50 amp breaker.
#14 for 3 hp with 30 amp breaker.

# 8 EGC from feeder panel.

 

[Dennis Alwon]

Doesn't article 430.52(C)(1) except. 1 allow for the next higher size breaker.

Also is the #12 on a 50 amp breaker allowed? 16.7*250%= 41.75= 45 amp breaker????

Not sure since you did not give the voltage I assumed 208 3 phase

 

[Lectricbota]

Doesn't article 430.52(C)(1) except. 1 allow for the next higher size breaker.

I don't think it applies to feeders though. ????

Also is the #12 on a 50 amp breaker allowed? 16.7*250%= 41.75= 45 amp breaker????

I think you're right. I've never seen a 45 amp CB and did not think they made them but it is listed in 240.6(A)

Not sure since you did not give the voltage I assumed 208 3 phase

It is 208 volts.


Appreciate the help, Dennis.

 

[jumper]

I don't think it applies to feeders though. ????

It doesn't. No next size up for motor feeder OCPDs.

430.62 Rating or Setting ? Motor Load.
(A) Specific Load. A feeder supplying a specific fixed motor
load(s) and consisting of conductor sizes based on
430.24 shall be provided with a protective device having a
rating or setting not greater than the largest rating or setting
of the branch-circuit short-circuit and ground-fault protective
device for any motor supplied by the feeder [based on
the maximum permitted value for the specific type of a
protective device in accordance with 430.52, or 440.22(A)
for hermetic refrigerant motor-compressors], plus the sum
of the full-load currents of the other motors of the group.