#1 fed by 150A CB

[lielec11]

I have an engineer of record saying a #1 can be fed from a 150A CB and a #4 can be fed from a 100A CB. Both branch circuits feed motor loads and they are sighting 430.32 as their backup. I don't see anything in that section that mentioned adequate cable protection. Is there another section they might be referring to? I just have it stuck in my head that the breakers are way to big to protect these feeders but I'd appreciate any other input.

 

[electrofelon]

I have an engineer of record saying a #1 can be fed from a 150A CB and a #4 can be fed from a 100A CB. Both branch circuits feed motor loads and they are sighting 430.32 as their backup. I don't see anything in that section that mentioned adequate cable protection. Is there another section they might be referring to? I just have it stuck in my head that the breakers are way to big to protect these feeders but I'd appreciate any other input.

You need to differentiate between motor overload protection and conductor ground fault and short circuit protection. Although you can do both with one device, often they are separate. The latter can be 250% the FLC if a breaker .

 

[electrofelon]

This may help

https://www.ecmweb.com/code-basics/motors-and-nec

 

[kwired]

I have an engineer of record saying a #1 can be fed from a 150A CB and a #4 can be fed from a 100A CB. Both branch circuits feed motor loads and they are sighting 430.32 as their backup. I don't see anything in that section that mentioned adequate cable protection. Is there another section they might be referring to? I just have it stuck in my head that the breakers are way to big to protect these feeders but I'd appreciate any other input.

430.32 is overload protection. Overload protection can be anywhere in the circuit as long as it will respond to usual load current.

430 part IV is short circuit and ground fault protection. That must be located at the beginning of the branch circuit.

430 Part II is motor circuit conductors - and covers minimum required conductor ampacity.

Short circuit/ground fault protection can be well above minimum required conductor ampacity.

Overload protection is going to be based on actual motor rated current.

 

[Dennis Alwon]

I have an engineer of record saying a #1 can be fed from a 150A CB and a #4 can be fed from a 100A CB. Both branch circuits feed motor loads and they are sighting 430.32 as their backup. I don't see anything in that section that mentioned adequate cable protection. Is there another section they might be referring to? I just have it stuck in my head that the breakers are way to big to protect these feeders but I'd appreciate any other input.

The overload protection in the motor will protect the conductors from being overloaded while the overcurrent protective device will protect the conductors from ground fault or short circuit protection. The overcurrent protective device is often higher than the ampacity of the conductors since T430.52 allows it.

 

[infinity]

I would follow what the engineer said. If you refer to post #2 you'll see that the OCPD could be up to 250% of the motor FLC. {Table 430.52}

 

[lielec11]

Thanks everyone.