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Motor Control Circuits

Motor Control CircuitsWhen specifying, installing, or modifying motor control circuits, you need to apply Article 430, Part V. This consists of Sections 430.71 through 430.75, and occupies a couple of pages.

To be efficient in applying the NEC requirements for motor control centers, understand that Part V has two main concerns:

  1. Overcurrent protection [430.72].
  2. Disconnection [430.75].

We’ll come back to those, after looking at two other important concerns.

The first of these appears throughout the NEC. It’s the admonition that you install the conductors so that they are protected from damage. This is actually a requirement for all electrical installations [110.27(B)]. But the specific text here (motor control circuits) modifies that by stating that if such damage would pose a hazard then the conductors of the remote motor control circuit must be run in raceway (or be otherwise protected from damage) [430.73].

The second has to do with handling ground faults if the circuit has a grounded conductor. If the remote motor control circuit has a grounded conductor, arrange the circuit so that a ground fault in it won’t start the motor and won’t bypass the shutdown devices (whether manual or automatic safety devices) [430.74].

Source: Mark Lamendola | Mindconnection