Motors, Part 3

Because it’s so large, Article 430 can seem overwhelming. But don’t let its size distract you. If you open your NEC to Article 430, you’ll notice Figure 430.1. This lays out the contents of Article 430 in the sequence of what you need to do to install a motor system.

Rather than wade through all of Article 430 to find requirements that might apply to whatever step you’re on, you can use Figure 1 to hone in on the requirements that do apply.

For certain applications, other articles may also apply [Table 430.5]. For example, hermetic motors are used in air conditioning and refrigeration systems. If you’re installing such a motor, you must apply Article 430 and Article 440.

The requirements of Chapters 1, 2, and 3 also apply to motor systems except where contradicted (amended) by Article 430. For instance, you still have to protect conductors from over current [240.3], but you wouldn’t follow the rule for the next size up to do so [240.6(A)].

With motor circuits, overload protection differs from how you’d normally do it. The two normal jobs of the overload protection device (OCPD) are split into two separate functions handled separately.

Normally, the branch circuit OCPD protects against overload and faults. But motor branch circuit OCPDs don’t handle overcurrent protection. They protect against short-circuit and ground-fault protection [Article 430, Part IV].

To protect motors, motor control apparatus, and motor branch circuit conductors against over current, delve into Part 3 for what applies to your application.

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