UL 20-2021 pdf download

UL 20-2021 pdf download.General-Use Snap Switches.
4 Construction 4.1 Enclosure 4.1.1 Switches shall be provided with complete enclosures that house all live parts, except that switches designed to be installed in device boxes or cut-out boxes or intended specifically for use in devices where they will be so enclosed as to prevent the exposure of live parts to accidental contact, need not be provided with such enclosures. 4.1.2 A key-operated switch shall be constructed so that a 0.5 mm (0.02 inch) diameter rigid steel wire cannot be inserted into the key slot so as to contact live electrical parts. 4.1.3 A metal enclosure of a switch (such as the cover of a surface-type switch or the shell of a fixture or pendant-type switch) shall be not less than 0.33 mm (0.013 inch) thick. Heavier metal shall be employed to provide strength and rigidity if the switch is rated more than 5 A, 250 V; 10 A, 125 V; or if the size or shape of the enclosure warrants such increased metal thickness. In Mexico, the following applies: A metal enclosure of a switch (such as a cover of a surface-type switch or the shell of a fixture or pendant-type switch) shall have the mechanical strength to enable it to comply with the specifications and test methods listed in this Standard. 4.1.4 A nipple (male or female) through which wires can pass shall have not less than five full, clean-cut threads of standard pitch as indicated in Table 1. The wireway provided by the nipple shall be free from burrs, fins, sharp edges, and the like that can damage wiring.
4.1.7 A threaded nipple for attachment to rigid metal conduit of the 1/2 inch or larger trade size shall be provided with a positive end stop for the conduit and a bushing, or an equivalent smooth, well-rounded surface, to prevent damage to wiring that enters the switch enclosure from the conduit. Note: Providing a positive end stop and bushing shall not be required fora hole tapped forrigid metal conduit in the wall of an outletboxorequivalentenclosure thatis providedwith a switch. 4.1.8 A switch intended to be exposed to a specific environment shall comply with the requirements of the Standards for Enclosures for Electrical Equipment, Non-Environmental Considerations, UL 50, Enclosures for Electrical Equipment, Environmental Considerations, UL 50E, CSA C22.2. No. 94.1, Enclosures for Electrical Equipment, Non-environmental Considerations, C22.2. No. 94.2, Enclosures for Electrical Equipment, Environmental Considerations, or NMX-J-235/1 ANCE, Enclosures for Electrical Equipment, Non-Environmental Considerations and NMX-J-235/2-ANCE, Enclosures for Electrical Equipment, Environmental Considerations. 4.1.9 A through-cord switch shall be provided with two distinct holes to accept and pass through the intended flexible cord. If a through-cord type switch is provided with one hole and provisions such as a knock out, the device is considered to be a pendant switch 4.1.10 A door switch shall be provided with an outlet box and cover plate.
4.2.2 An insulating lining shall be secured so that it will remain in place under conditions of intended service, and shall prevent the enclosure from becoming a live part even if a wire inside the switch should become loose or detached from its termination. The lining of the cover of a surface-type switch shall extend beyond the edge of the cover. 4.2.3 In switches having molded covers protected by a metal armor, the armor may be flush with the cover if the construction of the switch is such that the armor is not likely to make contact with any live parts when the cover is being put in place on the switch. 4.3 Bushings and Strain Relief 4.3.1 The cord-inlet hole in a pendant or through-cord switch that has a metal enclosure shall be provided with an insulating bushing or the equivalent. The material of the bushing shall be of porcelain, phenolic, or cold-molded composition, or other insulating material determined to be acceptable for the purpose. 4.3.2 Hard fiber may be provided as the insulating material if the bushing is not less than 1.19 mm (0.047 inch) thick and if it is formed and secured in place so that it will not be affected by conditions of ordinary moisture.UL 20-2021 pdf download.