Sizing Motor Circuit
- Thread starter sscottp
- Start date
- Location
- Illinois
- Occupation
- retired electrician
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.
The maximum OCPD for a thermal magnetic breaker is 250% of the table current or 450 amps.
It looks good to me.
- Location
- New Jersey
- Occupation
- Journeyman Electrician (retired)
The conductors are sized according to 125% of the FLC in TABLE 430.250 or 151*125%.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
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!
EngineeredElectric
Member
- Location
- Lockport IL
- Occupation
- Contractor
Wow that's a big fan. Please send pictures.
Thank you for this information. I did not mention that the length of wire is about 300' to 400' from the 400A breaker to the size 5 starter. I was assuming that the length of wire does not matter, is that correct?
- Location
- Illinois
- Occupation
- retired electrician
The length increases the voltage drop, so if lower voltage is an issue, you need to do a voltage drop calculation. You use the actual nameplate full load current for the voltage drop calculation, and not the current from Table 430.250.