wiring size

[guggemos]

I have a 2400V motor circuit with a 700HP motor that I'm replacing with a 150HP motor. Besides the fused starter changing from a 12R to a 3R and the CT's being resized does the feeder cable to the motor need to be downsized? Currently it is 3 #4/0. I can relug the motor connections if needed to accept the 4/0 wire.

 

[Dennis Alwon]

Even though T. 250.122 tells you what size the egc must be for a certain size breaker if you increase the ungrounded conductors for any reason then the egc must be upsized proportionately. That is the only issue I see with the whip to the unit. If the egc is the conduit on the line size of the disconnect then that is not an issue.

 

[masterinbama]

As long as the t head on the motor is big enough I would leave it as is.



With the grounding as Dennis said.

 

[Dennis Alwon]

I should have stated to read art. 250.122(B)

 

[kingpb]

I don't know what your lug size is, but you can check the Burndy pin terminals to see of you can go from 4/0 to whater the lugs can handle. This could save you having to change the lugs. These come in handy when running upsized conductos to cover for voltage drop.

 

[guggemos]

wiring size

Thanks, all.
I will check the lugs and keep the wiring the same.