Conductor size for 30hp 230 volt 3 phase motor

[GWB]

Full load is 75.4 amps so multiply by 125% gives me #1 thhn. (430.22) with #8 ground (250.122)
What about the conductors from the meter to the pump panel? The breaker is 100 amp at the pump panel...not sure about wire size from pump panel breaker to meter base. 430.24 says 125% of highest rated motor..but that is for a motor and other loads or several motors. This is just a pump panel supplying a motor, no other loads
This is an agricultural irrigation pump.
Thank you for your input.

 

[topgone]

Full load is 75.4 amps so multiply by 125% gives me #1 thhn. (430.22) with #8 ground (250.122)
What about the conductors from the meter to the pump panel? The breaker is 100 amp at the pump panel...not sure about wire size from pump panel breaker to meter base. 430.24 says 125% of highest rated motor..but that is for a motor and other loads or several motors. This is just a pump panel supplying a motor, no other loads
This is an agricultural irrigation pump.
Thank you for your input.

If it's a motor load, please refer to Table 430.52.

The guiding principle is to choose an overcurrent protection device that will be able to carry the motor's starting current but will trip the controller if the motor gets short-circuited.

 

[augie47]

(Note that in this case it may make no difference, but for all calculations other than overload, 430.6 directs you to use Tables 430.247-430.250 rather than nameplate values for most situations.)

In answer to your question, my opinion would be you could size the conductor from the meter to your breaker per 230.42

In regard to post #2, the 100 amp breaker does raise a few questions. Is it part of the pump controller ? If it's not integral with the pump controller, how was the size selected ?

 

[augie47]

Take a look at 230.90. As I read it your service can be sized the same as the branch circuit

 

[don_resqcapt19]

Will a standard 100 amp breaker let a motor with a full load of 75 amps start without tripping on the inrush?

 

[topgone]

Will a standard 100 amp breaker let a motor with a full load of 75 amps start without tripping on the inrush?

Good point!
That's basically what I was trying to point out when directing the OP to visit 430.52. Depending on the type of load being driven, a standard 100A breaker will probably trip before the starting current tapers off.

 

[hbendillo]

Will a standard 100 amp breaker let a motor with a full load of 75 amps start without tripping on the inrush?

It is questionable but it would depend on the locked-rotor-amps of that particular motor. That depends on the Code rating or label on the motor. It is standard practice to use 6 x RLA as the locked-rotor amps because we rarely know what the Code rating of the motor is at the design phase. Never had that fail me. The code requirements for sizing OCP for motors provides plenty of margin for error. Doesn't mean a smaller breaker wouldn't work though. I think your obligation ends at the pump controller. Provide a service based on your load calculations with a appropriately sized service disconnect.