NEMA publishes standards for boxes, covers, and supports

ROSSLYN, VIRGINIA - The National Electrical Manufacturers Association (NEMA) has published OS 1-2008 Sheet-Steel Outlet Boxes, Device Boxes, Covers, and Box Supports and OS 2-2008 Nonmetallic Outlet Boxes, Device Boxes, Covers, and Box Supports.

OS 1-2008 and OS 2-2008 describe standard configurations for outlet boxes 100 cubic inches or less, as well as manufacturer specifications for materials, corrosion protection, dimensions of openings, supports, cover screws, markings, and provisions for grounding. The standards specify dimensions necessary for compatibility with NEMA standard wiring devices and help manufacturers ensure that box constructions comply with the National Electrical Code as well as UL listing requirements.

“OS 1 and OS 2 are the essential industry standards for maintaining compatibility of metal and nonmetallic outlet boxes with standardized wiring devices and conduit and cable systems,” said Daniel Kissane, chairman of the Outlet & Switch Box Section.

“These revisions serve to increase both standards’ utility to manufacturers and building specifiers.”

The standards were last revised in 2003. Two of the changes made to OS 1 include additional marking requirements for boxes for ceiling-suspended fan support and clarification to marking requirements for clamps furnished as part of a box. OS 2 includes updated definitions, revised requirements for fixture boxes, and a modified Table 2-2.

The contents and scope of OS 1 may be viewed, or a hardcopy or electronic copy purchased for $129, by visiting The contents and scope of OS 2 may be viewed, or a hardcopy or electronic copy purchased for $82, by visiting Standards may also be purchased by contacting IHS at 800-854-7179 (within the U.S.), 303-397-7956 (international), 303-397-2740 (fax), or

NEMA is the association of electrical and medical imaging equipment manufacturers. Founded in 1926 and headquartered near Washington, D.C., its approximately 450 member companies manufacture products used in the generation, transmission and distribution, control, and end use of electricity.


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