19-inch Rack - Specifications

Specifications

The formal standards for a 19-inch (482.6 mm) rack are available from the following:

• Electronic Industries Alliance EIA-310-D, Cabinets, Racks, Panels, and Associated Equipment, dated September 1992. (Latest Standard Now REV E 1996)
• Consumer Electronics Association CEA-310-E design requirements for Cabinets, Panels, Racks and Subracks., dated December 14, 2005
• International Electrotechnical Commission - Multiple documents are available in French and English versions.
  • IEC 60297 Mechanical structures for electronic equipment - Dimensions of mechanical structures of the 482,6 mm (19 in) series
    • IEC 60297-1 Replaced by IEC 60297-3-100
    • IEC 60297-2 Replaced by IEC 60297-3-100
    • IEC 60297-3-100 Part 3-100: Basic dimensions of front panels, subracks, chassis, racks and cabinets
    • IEC 60297-3-101 Part 3-101: Subracks and associated plug-in units
    • IEC 60297-3-102 Part 3-102: Injector/extractor handle
    • IEC 60297-3-102 Part 3-103: Keying and alignment pin
    • IEC 60297-3-104 Part 3-104: Connector dependent interface dimensions of subracks and plug-in units
    • IEC 60297-3-105 Part 3-105: Dimensions and design aspects for 1U chassis
    • IEC 60297-4 Replaced by IEC 60297-3-102
    • IEC 60297-5 Multiple documents, -100, 101, 102, ... 107, replaced by IEC 60297-3-101
• Deutsches Institut für Normung DIN 41494 - Multiple documents in German but some documents are available in English.
  • DIN 41494 Equipment practices for electronic equipment; mechanical structures of the 482,6 mm (19 inch) series
    • DIN 41494-7 Dimensions of cabinets and suites of racks.
    • DIN 41494-8 Components on front panels; mounting conditions, dimensions
    • DIN IEC 60297-3-100 (see above in IEC section)

A rack's mounting fixture consists of two parallel metal strips (also referred to as "posts" or "panel mounts") standing vertically. The posts are each 0.625 inches (15.88 mm) wide, and are separated by a gap of 17.75 inches (450.85 mm), giving an overall rack width of 19 inches (482.60 mm). The posts have holes in them at regular intervals, with both posts matching, so that each hole is part of a horizontal pair with a center-to-center distance of 18.312 inches (465.12 mm).

The holes in the posts are arranged vertically in repeating sets of three, with center-to-center separations of 0.5 inches (12.70 mm), 0.625 inches (15.88 mm), 0.625 inches (15.88 mm). The hole pattern thus repeats every 1.75 inches (44.45 mm).

Holes so arranged can either be tapped (usually 1⁄₄-inch UNC thread, more seldom metric 5 or 6 mm) or square. The square holes are meant for cage nuts. Tapped holes are more common in USA whereas square holes for cage nuts are common in Europe, especially in German cabinetry.

Racks are divided into regions, 1.75 inches (44.45 mm) in height, within which there are three complete hole pairs in a vertically symmetric pattern, the holes being centered 0.25 inches (6.35 mm), 0.875 inches (22.23 mm), and 1.5 inches (38.10 mm) from the top or bottom of the region. Such a region is commonly known as a "U", for "unit", or in German "HE" (for Höheneinheit) and heights within racks are measured by this unit. Rack-mountable equipment is usually designed to occupy some integer number of U. For example, an oscilloscope might be 4U high, and rack-mountable computers are most often 1U or 2U high. A blade server enclosure might require 10U. Occasionally, one may see fractional U devices such as a 1.5U server, but these are much less common.

The height of a rack can vary from a few inches, such as in a broadcast console, to a floor mounted rack whose interior is 45 rack units (78.75 inches / 200 centimetres) high. Many wall-mounted industrial equipment enclosures have 19-inch rack rails to support mounting of equipment.