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AutoQuiz: What Type of Electrical Enclosure Resists Corrosion and Provides Protection?

AutoQuiz is edited by Joel Don, ISA's social media community manager.

Today's automation industry quiz question comes from the ISA Certified Automation Professional certification program. ISA CAP certification provides a non-biased, third-party, objective assessment and confirmation of an automation professional's skills. The CAP exam is focused on direction, definition, design, development/application, deployment, documentation, and support of systems, software, and equipment used in control systems, manufacturing information systems, systems integration, and operational consulting. Click this link for information about the CAP program. The following question comes from the CAP study guide, Performance Domain III, System Design: Design, specify, and procure the hardware/software used in the system.


If you need an enclosure that resists corrosion and provides protection for outdoor use, dust, and hose-directed water, which type of enclosure would you select?

a) Type 1 (NEMA 1)
b) Type 4x (NEMA 4x)
c) Type 12 (NEMA 12)
d) Type 13 (NEMA 13)
e) None of the above


NEC (National Electrical Code) 2002 defines an enclosure Type 4x as ideal for outdoor use and resistant to splashing water, windblown dust, hose directed water, and corrosion. It is also undamaged by the formation of ice on the enclosure.

A Type 1 enclosure is for indoor use.

A Type 12 enclosure is for indoor use and resists only dust and dripping non-corrosive liquids.

A Type 13 enclosure is for indoor use and resists dust, spraying water, oil, and non-corrosive coolants.

The correct answer is B, Type 4x (NEMA 4x).

Reference: Mark W. Earley, Editor; NEC 2002 Handbook; NFPA, 2002


Joel Don
Joel Don
Joel Don is the community manager for ISA and is an independent content marketing, social media and public relations consultant. Prior to his work in marketing and PR, Joel served as an editor for regional newspapers and national magazines throughout the U.S. He earned a master's degree from the Medill School at Northwestern University with a focus on science, engineering and biomedical marketing communications, and a bachelor of science degree from UC San Diego.

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