Disconnect switch standards and test procedures

UL (Underwriters Laboratories) and NEMA (National Electrical Manufacturers Association) design standards and NEC (National Electrical Code) installation practices are reviewed to provide a better understanding of safety switch product capabilities and applications. The test procedures applicable to switch products are discussed. Application requirements outside the parameters of these tests should be considered unusual applications and should be reviewed with the manufacturer. The standards as they relate to products listed as general duty and heavy duty are considered. Product life and service requirements are related to the choice of a heavy or general duty switch, depending on the nature of the application. The standards for enclosure test procedures relating to the various enclosure types are described. As defined, enclosures are intended to provide a degree of protection to the equipment within them, and an understanding of the construction requirements will aid in identifying the correct type for common application needs. Also included ar misapplication issues that are sometimes assumed by untrained personnel who utilize the general descriptions of these enclosure types without a thorough understanding of the applicable design standards.<>