The table "NEMA and IEC enclosure comparison" shown in "Enclose as Needed" (CE, p. 58, March 2006; www.controleng.com/archive) could be construed by readers as a direct one-to-one correlation and interchangeability from IEC IP [ingress protection] Code-rated enclosures to NEMA Type-rated enclosures. No such direct conversion is possible.
The table “NEMA and IEC enclosure comparison” shown in “Enclose as Needed” ( CE , p. 58, March 2006; www.controleng.com/archive ) could be construed by readers as a direct one-to-one correlation and interchangeability from IEC IP [ingress protection] Code-rated enclosures to NEMA Type-rated enclosures. No such direct conversion is possible. Many electrical inspectors in the U.S. who apply the National Electrical Code (NEC) will not approve installations where an enclosure has only an IP Code rating with no NEMA Type rating.
IEC IP Code only addresses requirements for protection of people, ingress of solid objects, and ingress of water. Many other requirements covered by NEMA Type standards that are not covered in the IEC IP Code, include construction requirements; door and cover securement; corrosion resistance; effects of icing; gasket aging and oil resistance; and coolant effects.
NEMA Type designation specifies requirements for these additional performance protections. For this reason, the IEC enclosure IP Code designations cannot be converted to NEMA enclosure Type numbers.
NEMA Standards Publication, “A Brief Comparison of NEMA 250 and IEC 60529,” provides additional information and is available for free download from NEMA at www.nema.org .
James R. Reizner is with Corporate Engineering; Power, Controls and Information Systems, The Procter & Gamble Co., www.pg.com
