National Electrical Code Articles and Information

Code Quiz: Article 440

Based on the 2020 NEC

Questions and answers written by Mark Lamendola, who has worked as a master electrician, electrical inspector, and design engineer. Mark is an IEEE Senior Member, and the Code article author for Codebookcity.com. Since 1996, he has been writing National Electrical Code articles for electrical trade magazines and has an extensive portfolio of hundreds of NEC articles.

Article 440 provides the requirements for hermetic motors. As the name implies, these motors are hermetically sealed. They are used for refrigeration equipment. Article 440 does not replace Article 430, it amends it except as noted in Article 430. Typically, each equipment manufacturer does the conductor and protection calculations for the equipment and puts this information on the nameplate. You should not need to perform these calculations when installing a chiller or similar equipment. If the information is missing or seems to be wrong on its face, contact the manufacturer before proceeding. That also applies to the disconnecting means.

1. If you use EMT as the raceway for a roof-mounted AC unit, what must go inside the EMT?
   

2. What's the minimum amperage rating of the disconnect for a hermetic compressor motor?
   
3. Which is a better location for the disconnect of an outdoor compressor, on the side of the building or on a panel of the unit?
   
4. If the conductors supply a motor-compressor load in addition to other loads, what's the minimum ampacity for that conductor?
   
5. Can you use a time delay breaker for short-circuit and ground-fault protection of a motor-compressor branch circuit?

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