Breaker sizing

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hhsting

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Glen bunie, md, us
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I have pizza shop that has Commercial kitchen. SEF-1 fan inside duct for smoke/economizer with 5hp breaker sizing 208V three phase. What is the breaker size for this according to NEC 2017? 40A is provided
 
What does manufacturer specify? Did you review 430? If this is existing equipment, is it be changed or modified which would require the circuit breaker to be replaced?
 
hhsting said:
I have pizza shop that has Commercial kitchen. SEF-1 fan inside duct for smoke/economizer with 5hp breaker sizing 208V three phase. What is the breaker size for this according to NEC 2017? 40A is provided
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You tell us what you came up with, let us tell you if your right.
we should treat this like a test question....

:unsure:
 
No one said it was a test question. The comment was "treat it as a test question"
Same theory applies:
If we simply give you the answer, you will ask again on the next motor.
If you do the calculation yourself and confirm it with us, the next time you will be more confident.
 
My Sq D motor data calculator has a 3 ph 200 volt motor at 17.5 FLC (average) and gives the circuit breaker size at 35 amps.
Your 12.78 seems low, what is the nampeplate A on the motor?
This would be a good test question.
 
The question remains.. where did the 12.78 come from....
sting needs to learn what Dennis is trying to teach him or he will be back every time he wants to check a breaker size.
 
Dennis Alwon said:
Yeah but for motor overcurrent protective device we should be using the FLC of the motor not Table 430.250. We use that table for conductor sizing. Somewhere we need to know the FLC of the motor.
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Is this right? I thought GF/SC OCPD was table. The OL is from actual nameplate. I’ll add section ref when back at code book.
 
And that seems to be correct and coming from 430.6(A)(1) and (2). My underlines.

430.6(A)(1) Table Values. Other than for motors built for low speeds
(less than 1200 RPM) or high torques, and for multispeed
motors, the values given in Table 430.247, Table 430.248,
Table 430.249, and Table 430.250 shall be used to determine
the ampacity of conductors or ampere ratings of switches,
branch-circuit short-circuit and ground-fault protection,
instead of the actual current rating marked on the motor
nameplate.

430.6(A)(2) Nameplate Values. Separate motor overload protection
shall be based on the motor nameplate current rating.
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Dennis Alwon said:
Yeah but for motor overcurrent protective device we should be using the FLC of the motor not Table 430.250. We use that table for conductor sizing. Somewhere we need to know the FLC of the motor.
Click to expand...
Isn't the nameplate used for overload devices not the CB feeding the motor as per post #17?
 
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