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NEC: Air Conditioning and Refrigerating Equipment — Part 3

Jan. 3, 2023
Article 440, Part 3 provides the requirements for the branch-circuit short-circuit and ground-fault protection used in HVAC and refrigeration equipment.

Article 440, Part 3 provides the requirements for the branch-circuit short-circuit and ground-fault protection used in HVAC and refrigeration equipment. That is, it provides the requirements for overcurrent protective devices (OCDPs) for hermetic motor circuits.

These requirements are not standalone, however. They supplement or amend the overcurrent protection requirements that apply to non-hermetic motor circuits [440.21]. This fact can make compliance a bit tricky. So here’s a pro tip: Proceed as if you are installing a non-hermetic motor, then look in Art. 440, Part 3 to see if there is an applicable set of requirements.

For example, suppose you are sizing the OCPD for an individual motor-compressor. You proceed as if you are sizing the OCPD for an individual non-hermetic motor. You start with the requirements in Art. 430. But that’s a big Article — how can you quickly locate the requirements? Go to Figure 430.1. You will see on the fourth tier of the drawing, “Motor branch-circuit short-circuit and ground-fault protection.” Part 4 is right across from it. Bingo.

When you go to 430 Part IV, you’ll see “430.52. Rating or Setting for Individual Motor Circuit.” This corresponds with “440.22. Single Motor-Compressor.” 430.52 underwent heavy revision with the 2023 cycle, and now you’re going to effectively revise it again by noting and applying the differences in 440.22. Before you read through the 430.52 requirements, understand what the 440.22 requirements are. And if you’ll notice, they are much simpler. No need to mess with Table 430.52(C)(1) and the rating rules that follow. All you have to do is use an OCPD that can carry the starting current and that does not exceed the greater of two values:

  1. 175% of the motor-compressor rated-load current.
  2. 175% of the branch-circuit selection current.

But you may need to use one of the two Exceptions if you can't start the motor by following the 175% rule.

Now, there is an even bigger shortcut that may exist for your particular installation. In many cases, the manufacturer has designed a “ready-to-go” package. If you install a Brand X Model 123XYZ HVAC unit, it is likely the manufacturer has already determined what disconnect and OCPD to use. The manufacturer does this for multiple reasons, such as reducing support tickets and warranty claims. If you’re putting together a bill of materials for installing such a system, check the installation instructions to see if this work has already been done for you.

About the Author

Mark Lamendola

Mark is an expert in maintenance management, having racked up an impressive track record during his time working in the field. He also has extensive knowledge of, and practical expertise with, the National Electrical Code (NEC). Through his consulting business, he provides articles and training materials on electrical topics, specializing in making difficult subjects easy to understand and focusing on the practical aspects of electrical work.

Prior to starting his own business, Mark served as the Technical Editor on EC&M for six years, worked three years in nuclear maintenance, six years as a contract project engineer/project manager, three years as a systems engineer, and three years in plant maintenance management.

Mark earned an AAS degree from Rock Valley College, a BSEET from Columbia Pacific University, and an MBA from Lake Erie College. He’s also completed several related certifications over the years and even was formerly licensed as a Master Electrician. He is a Senior Member of the IEEE and past Chairman of the Kansas City Chapters of both the IEEE and the IEEE Computer Society. Mark also served as the program director for, a board member of, and webmaster of, the Midwest Chapter of the 7x24 Exchange. He has also held memberships with the following organizations: NETA, NFPA, International Association of Webmasters, and Institute of Certified Professional Managers.

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