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Hermetic Motors, Part 1

Hermetic Motors, Part 1Hermetic motors are used in air-conditioning and refrigeration equipment. What makes them “hermetic” is the fact that the motor itself is immersed in the refrigerant and the case is sealed tight. This arrangement means there are different cooling and other characteristics for these motors compared to non-hermetic motors.

Because of those characteristics, the NEC provides special requirements for the installation, wiring, and circuit protection of hermetic motors.

True or false? The requirements for hermetic motors are in Article 440.

False. Article 440 provides some of the requirements for hermetic motors, not “the” requirements. These are in addition to, or amend, the requirements of Article 430 (motors) and other requirements in the NEC [440.3].

To avoid confusion and rework when installing these motors or the circuits that supply them, work from Article 430 but refer to the applicable Part of Article 440 when doing so. For example, you’re sizing the branch-circuit protection. That would be Part IV of Article 430 (see Figure 430.1 to quickly find the applicable Part) and Part III of Article 440. Need to select the controller? That would be Part VII of Article 430 and Part IV of Article 440.

If the motor involves an appliance, you’ll also need to refer to Article 422. If it involves fixed space heating equipment, you’ll also need to refer to Article 424.

Table 440.3(D) lists additional (possibly applicable) Articles by equipment/occupancy.

Part 2 » | Source: Mark Lamendola | Mindconnection