Selecting between NEMA Enclosure Types and IEC Enclosure Classifications

The National Electrical Manufacturers Association (NEMA) has developed and maintained a standard set of definitions for various types of electrical enclosures found in industrial applications. Each type reflects certain levels of environmental conditions and personal protection against hazardous situations such as flying debris. The following tables 1, 2, and B-1 can be used as reference in determining the correct NEMA enclosure type for an indoor or outdoor application; the definitions of each type can be found in detail here.

NEMA Enclosure Types

Table 1 – Comparison of Specific Applications of Enclosures for Indoor Nonhazardous Locations

NEMA enclosure types for indoor nonhazardous locations

Table 2 – Comparison of Specific Applications of Enclosures for Outdoor Nonhazardous Locations

NEMA enclosure types for outdoor nonhazardous locations

Table B-1 – Comparison of Specific Applications of Enclosures for Indoor Hazardous Locations

NEMA enclosure types for indoor hazardous locations

(Note: if the installation is outdoors and/or additional protection is required by Tables 1 or 2, a combination-type enclosure is required)

In contrast to NEMA, whose standards apply within North America, the International Electrotechnical Commission (IEC) has developed their own set of standards (IEC 60529) which are defined by the degree of protection provided by the enclosure. The IEC designations are identified by the letters “IP” (Ingress Protection, followed by two numerals, as detailed below:

IEC Enclosure Classification Designations (IP Ratings)

IEC classification designations aka IP ratings

These IEC enclosure designations do not take into consideration the risk of explosions, damage of mechanical equipment, or environmental factors such as moisture; for that reason, NEMA enclosure types cannot directly be equated to IP ratings. However, the following table A-1 can be used to convert NEMA enclosure type ratings to a comparable IP rating.

Table A-1 – Conversion of NEMA Enclosure Type Ratings to IEC 60529 Enclosure Classification Designations (IP)

Conversion of NEMA enclosure types to  IEC enclosure classification designations

(note: This table cannot be used to convert IEC Classification Designations to NEMA Type Ratings)

Sources: NEMA Enclosure Types (nema.org), Siemens Industrial Controls Catalog 2010

Julyann Tu is an application engineer for AWC, Inc. in the Houston, TX office. She is a Certified Siemens Technology Specialist for Factory Automation and a SITRAIN Certified Instructor for TIA Portal Programming 1. With over 8 years of experience in industrial automation, she has a BS in Industrial Engineering from Texas A&M University and an MBA from University of Houston-Clear Lake.

Julyann Tu

App Engineer/
Tech Support

Julyann Tu

App Engineer/
Tech Support

Julyann Tu is an application engineer for AWC, Inc. in the Houston, TX office. She is a Certified Siemens Technology Specialist for Factory Automation and a SITRAIN Certified Instructor for TIA Portal Programming 1. With over 8 years of experience in industrial automation, she has a BS in Industrial Engineering from Texas A&M University and an MBA from University of Houston-Clear Lake.
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