The National Electrical Manufacturers Association (NEMA) recently published NEMA OS 3-2012, "Selection and Installation Guidelines for Electrical Outlet Boxes." Guidelines for selection and installation of general purpose and specialty metallic, nonmetallic, and composite outlet boxes such as device boxes, boxes for luminaires or other products, and junction boxes; extension rings; covers; and flush-device cover plates are covered in this publication. The boxes addressed in these guidelines are intended for use in ordinary, non-hazardous locations. With the exception of masonry boxes and some multi-gang and floor boxes, the boxes addressed in these guidelines are limited to 1650 cm³ (100 in.³) internal volume per gang.
NEMA OS 3-2012 may be downloaded at no charge or purchased in hardcopy for $91 by visiting NEMA’s website or by contacting IHS by phone at (800) 854-7179 (within the United States) or
(303) 397-7956 (international), or by visiting global.ihs.com.