- Location
- New Jersey

- Occupation
- Journeyman Electrician

- Thread starter infinity
- Start date

- Location
- New Jersey

- Occupation
- Journeyman Electrician

- Location
- Illinois

Take a look at 430.22(C). Assuming a 480 volt motor, you can use #1 copper for the motor circuit conductors.

I missed the the derating...#1 is too small. Assuming a 90?C conductor, 1/0 is code compliant.

I missed the the derating...#1 is too small. Assuming a 90?C conductor, 1/0 is code compliant.

Last edited:

I agree.Take a look at 430.22(C). Assuming a 480 volt motor, you can use ... 1/0 is code compliant.

- Location
- New Jersey

- Occupation
- Journeyman Electrician

Sorry, yes a 90? C conductor (THHN).Take a look at 430.22(C). Assuming a 480 volt motor, you can use #1 copper for the motor circuit conductors.

I missed the the derating...#1 is too small. Assuming a 90?C conductor, 1/0 is code compliant.

If someone could check my math here's what I came up with:

150 hp @ 480 volts = 180 amps {T430.250}

180 amps * 72% = 130 amps {430.22(C)}

130 amps/80% = 162.5 amps minimum conductor ampacity {6 CCC's in single raceway, 80% derating}

#1/0 THHN @ 90? C = 170 amps

- Location
- Illinois

That is the same that I came up with.Sorry, yes a 90? C conductor (THHN).

If someone could check my math here's what I came up with:

150 hp @ 480 volts = 180 amps {T430.250}

180 amps * 72% = 130 amps {430.22(C)}

130 amps/80% = 162.5 amps minimum conductor ampacity {6 CCC's in single raceway, 80% derating}

#1/0 THHN @ 90? C = 170 amps

- Location
- New Jersey

- Occupation
- Journeyman Electrician

Thanks. I need to show this calculation to someone who told me the correct size was #4/0.

... Just a thought

- Location
- New Jersey

- Occupation
- Journeyman Electrician

More than likely, I'm incorrect,,,, in any event, it would seem the motor FLA would be distributed.

Your calculation is most likely correct.... it simply went th ru my mind that we are using larger conductors than an ACL situation would require.

Yes. The motor has twelve leads for six windings (OP said 480 single voltage motor so I have to wonder about that). Winding leads are paired at motor terminal box so that only six conductors needed externally, i.e. for three sets of windings. You essentially have three 2-wire subcircuits. All wires conduct in both start and run modes.

- Location
- New Jersey

- Occupation
- Journeyman Electrician

Nameplate:Yes. The motor has twelve leads for six windings(OP said 480 single voltage motor so I have to wonder about that). Winding leads are paired at motor terminal box so that only six conductors needed externally, i.e. for three sets of windings. You essentially have three 2-wire subcircuits. All wires conduct in both start and run modes.

Wiring Diagram:

Okay... it has 12 leads for optional part winding start, rather than dual voltage.Nameplate: ...

PS: My next most recent post should have started "No" rather than "Yes". My brain interpretted your post as saying "correct" instead of "incorrect".

Last edited:

- Location
- Tacoma, Wa

- Location
- federal way,washington