9 motors new install

[CodyGtx]

Just trying to verify if I’m right and that I did my calculations right. I have 9 of the same size blower motors in a cooler. All motors are 3 phase 480v 3hp with a 1.00 starting factor.
I figured I’d run 3 circuits off a 3pole 40a breaker using 10 wire and each breaker. 1 breaker would feed 3 motors. Of course using disconnect means at motor. Is this sufficient?
Thanks

 

[veraniumhydroxide]

I think it is ok. and breaker of each blower should be 20A.

 

[CodyGtx]

I think it is ok. and breaker of each blower should be 20A.

I got 15amp breaker for (1)3hp motor. But obviously I don’t want to Install 9 3pole breakers in existing panel. Don’t have that kind of room

 

[Besoeker3]

I think it is ok. and breaker of each blower should be 20A.

Seems a bit excessive for a 2.2 kW motor.....

 

[infinity]

Would Table 430.52 limit an inverse time circuit breaker to 250% of the motor FLC which from table 430.250 is 4.8 amps?

 

[augie47]

Would Table 430.52 limit an inverse time circuit breaker to 250% of the motor FLC which from table 430.250 is 4.8 amps?

Agree.
Unless you have some other short circuit means, you would be limited to a 15 amp breaker.
How are you addressing overload protection ?

 

[bwat]

with a 1.00 starting factor.

Minor note. I’m guessing you meant “service” factor.

 

[CodyGtx]

Agree.
Unless you have some other short circuit means, you would be limited to a 15 amp breaker.
How are you addressing overload protection ?

Yes so 3 motors times 4.8 is 14.4amps. I can probably get away with 12 wire but now for overload protection14.4 amps time 250% is 36 which is why I was thinking I need 40 amp breaker

 

[ptonsparky]

Each motor needs overcurrent protection. How are you providing that?

I would consider your 40 amp CB as protection of the feeder to your three motor controllers. They could be VFDs, manual starters, across the line starters or a set of fuses in your motor disconnect.

 

[infinity]

Yes so 3 motors times 4.8 is 14.4amps. I can probably get away with 12 wire but now for overload protection14.4 amps time 250% is 36 which is why I was thinking I need 40 amp breaker

You're math incorrect it's 4.8*250%=12 amps maximum for each motor.

 

[kwired]

Maximum short circuit/ground fault protection is 250% for inverse time breaker and 175% for time delay fuse, next higher standard device is permitted (from 240.6).

Lowest standard circuit breaker is 15 amps, therefore you can have however many motors a 15 amp breaker will let you start, three probably will start in many cases but could be a few you get no more than two.

If using fuses 10 amps is a standard size. Again however many motors that 10 amp fuse will let you start is likely the practice you will follow, may only be able to start one motor in some cases here, but I'd bet majority of time you could start two.

If 15 amps is highest circuit breaker you can use no reason to use larger than 14 AWG conductors besides to counter voltage drop.