Michael Hazell

NEC Question of the Week takes on differences between requirements in NFPA 70 and 79

Blog Post created by Michael Hazell Employee on Oct 9, 2013

Each week, nec connect, NFPA’s online resource for all things related to the National Electrical Code® (NEC®), offers a question and answer about the Code, electrical safety, wiring, guidelines, and equipment, and other timely topics. Here is this week's question: 

Question: Are there some significant differences between the NEC® and 2015 NFPA 79 (Electrical Standard for Industrial Machinery) requirements?

Answer: Yes. To highlight the differences and peculiar conditions involved with machine tools that warrant exception to certain specific NEC requirements, 11.5.1.2 was revised to address the use of control cabinets on machines as opposed to them seldom being used in NEC applications and reads:
The width of the working space in front of control cabinets and compartments shall be the width of the opening of the control cabinet, or 762 mm (30 in), whichever is greater. Where control equipment or devices are mounted on or through the fixed area around the opening into the control cabinet or compartment, the width of the working space in front of the control cabinet or compartment shall include the width of the fixed area containing the control equipment and devices.

Further, 11.5 had language added to address what rules apply, those of the NEC or NFPA 79 when Industrial Machines are involved.

Working Space for cabinets and compartments that contain supply conductors to Industrial Machinery, that are covered by NEC Article 670 shall be in accordance with the NEC.

This change correlates the NFPA 79 requirements with the Informational Note to 670.1 in the NEC. The terms cabinets and compartments are used to be consistent with the terminology within the document. An (*) was added to point to the newly added Annex A material. This addresses the directive of the Correlating Committee note 1 to reconsider the actions on Public Input 94. The Annex material provides drawings that clearly show where the scope of each document applies.

Additionally, several exceptions already exist in 11.5 to address the specific working space conditions of industrial machinery.

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