UL 50:2003 pdf download Enclosures for Electrical Equipment
5 General
5.1 An edge on an enclosure shall not be sufficiently sharp to constitute a risk of injury in normalmaintenance or use.
5.2 An enclosure shall be made of iron, steel, brass, copper, or aluminum.
Exception:Other material may be used if the material is investigated and found to be acceptable and theenclosure has at least the equivalent strength and rigidity.
5.3 Both the inside and outside surfaces of an enclosure, including means for fastening, shall beprotected against corrosion by enameling, galvanizing, plating, or other equivalent means.
Exception No. 1: An enclosure and means for fastening that are of metal that is inherently resistant tocorrosion.
Exception No. 2: This requirement does not apply to.
a) Bearings, sliding surfaces of a hinge, or shaft and the like where such protection isimpractical; and
b) Parts made of stainless steel.
5.4 The outside of a cast-aluminum enclosure marked in accordance with 50.4 shall be coated withasphalt paint, one coat of baked enamel, or other material that provides equivalent protection.5.4 revised November 19.1999
5.5 An enclosure shal have the necessary strength and rigidity to maintain its shape so that an enclosuredoor closes tightly.
5.5 revised October 1, 1996
5.6 Metal into which screws are threaded shall provide for the engagement of at least two full threadsRivets, screws, bolts, and similar fastenings in a sheet-metal enclosure shall have a diameter at least 50percent greater than the thickness of the finished sheet metal with which they are used.
5.7 A screw with 32 threads per inch (32 threads per 25.4 mm) installed in 0.053 inch (1.35 mm) thickminimum sheet metal shall be considered acceptable.
5.7 revised November 19.1999
5.8 Sheet metal may be extruded at a tapped hole to give the thickness necessary for two full threads ifthe original thickness is not less than the pitch of the thread.
5.9 A fastener for use with a conventional screw, other than a tapped hole or nut, is acceptable if it hasthe necessary mechanical strength and is otherwise acceptable for the application.
5.10 Neutral terminals and eauipment-arounding terminals provided as part of an enclosure are evaluatedin accordance with the Standard for Panelboards, UL 67, and with regard to their intended use.
ENCLOSURES
6General
6.1 A complete enclosure shall be provided for all live parts that may be housed in it.6.1 revised October 1, 1996
6.2 An enclosure flange, or the side wall of an enclosure, may be punched to form an ear that may bebent out to facilitate the mounting of the enclosure or to form a bracket for securing a trim, provided that’
a) There is no direct opening into the enclosure when the ear is in any position; and
b) The overlap between the edges of the opening and the edge of the flange or other closingmetal is not less than 1/8 inch (3.2 mm).
6.3 An enclosure shall be one or more of the types defined in Table 6.1 and described in Table 6.2.
Exception: An enclosure marked in accordance with 50.4.