Industrial Panel Wiring

[plsticsman]

According to NEC, what feeder wire do I need to run from a (values made up, but it helps with the point) 150A, 3 phase main panel breaker to a 60A, 3 Phase breaker feeding a motor starter? Does the wiring from the 150A to the 60A have to be sized for 60A or 150A??? And does anyone know the NEC reference to show this?

 

[roger]

Re: Industrial Panel Wiring

You will be able to work yourself through this starting with article 430.

The motor starter is not what will determine the feeder.

Roger

[ August 16, 2004, 04:38 PM: Message edited by: roger ]

 

[steve66]

Re: Industrial Panel Wiring

In general, conductors have to be protected at their ampacity, and the protection has to be at the supply to the conductor (240.4). However, 240.4 also lists some exceptions. Look at 240.4 (G) and the table. You use article 430 parts III-VII to determine wire sizes and overcurrent protection for motor circuits.

You are calling this a feeder (refer to figure 430.1), and I assume it only feeds a single motor. So refer to 430.22 to size the feeder.

Also, you gave two arbitrary size breakers. Notice that they would have to be sized per Part V and Part IV (again refering to 430.1).

Steve

 

[tom baker]

Re: Industrial Panel Wiring

In general a motor feeder or branch circuit is sized at the value in table 430.22 E (I'm not giving it to you so you will look it up). The type motor duty and its table value (430.148, 149,..)determine the size of the conductors.