Motors
- Thread starter scs
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bphgravity
Senior Member
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- Florida
Re: Motors
The feeder overcurrent protection for for several motors is found in Article 430.62. Basically, take the largest branch circuit overcurrent device and add the FLC of the rest of the motors connected to the same feeder.
This is one situation in which the code does not permit going up to the next standard size OCD.
The feeder overcurrent protection for for several motors is found in Article 430.62. Basically, take the largest branch circuit overcurrent device and add the FLC of the rest of the motors connected to the same feeder.
This is one situation in which the code does not permit going up to the next standard size OCD.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: Motors
Remember when sizing motor circuits, the NEC requires you to use the ampere values in the table from 430, not the actual nameplate values.
Likewise, when choosing the final running current protective device, you should use the actual nameplate values and not the ones from tables. For instance, the Square D Motor Data slide rule lists the ampacity from the NEC (i.e. 10HP, 480V = 14A), however the "thermal unit" selection comes from some statistically safe formula (the suggested B25 is based on 12.8A)
Remember when sizing motor circuits, the NEC requires you to use the ampere values in the table from 430, not the actual nameplate values.
Likewise, when choosing the final running current protective device, you should use the actual nameplate values and not the ones from tables. For instance, the Square D Motor Data slide rule lists the ampacity from the NEC (i.e. 10HP, 480V = 14A), however the "thermal unit" selection comes from some statistically safe formula (the suggested B25 is based on 12.8A)
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