Sizing Motor Circuit

[sscottp]

Is it allowable to install a 4/0 AWG CU circuit on a 400A breaker for a 3-phase 480V 150HP Fan? The 4/0 conductor is installed to a Size 5 starter which has another breaker and overloads sized for the 150HP.

 

[don_resqcapt19]

The full load current in Table 430.250 for a 3 phase, 460 volt, 150 hp motor is 180 amps. The minimum conductor size, per 430.22 is 125% of 180 amps or 225 amps. 4/0 copper is 230 amps so the conductor is good.
The maximum OCPD for a thermal magnetic breaker is 250% of the table current or 450 amps.
It looks good to me.

 

[infinity]

The conductors are sized according to 125% of the FLC in TABLE 430.250 or 151*125%.

 

[Jraef]

The conductors are sized according to 125% of the FLC in TABLE 430.250 or 151*125%.

I guess it depends on if this is in Canada (575V) or the US (460V). OP never said, but their profile says Colorado so unless they are on a long road trip north, 150HP 460V is 180A.

Don FTW!