UL-1640:2012 pdf free download – STANDARD FOR SAFETY Portable Power-Distribution Equipment.
9.4.2.3 For supported surfaces, measure width and enter table at Column 3. If dimension of Column 4 is “not limited”, determine minimum thickness from Column 5 or 6, as appropriate, If dimension of Column 4 is numerical, the length may not exceed that value for the thickness of Column 5 or 6. If the length exceeds the numerical value, it is necessary to drop to the next line in column 5 or 6 to determine minimum thickness.
7.4.2.4 For nonsupported surfaces, measure width. Enter Table at Column 1. If dimension of Column 2 is “not limited”, determine minimum thickness from Column 5 or 6, as appropriate. If dimension of Column 2 is numerical, the length shall not exceed that value for the thickness of Column 5 or 6. If the length exceeds the numerical value, it is necessary to drop to the next line in column 5 or 6 to determine minimum thickness.
9.4.2.5 If thickness determined is not provided, “Body Stiffeners,”“Reinforcing Ribs,”“Cross Frames,” and the like shall not be used unless investigated and determined to be suitable for the purpose.
9.4.2.6 If two or more covers or panels are provided to close a single opening, the thickness of each cover or panel shall not be less than a single sheet as specified in Tables 9.1 and 9.2. The adjacent edges of such multiple panels or covers shall:
a) Be flanged at least 1/2 inch (12.7 mm); or
b) Be supported against an inward force at 10 inch (254 mm) maximum intervals; or
c) Overlap each other at least 1/2 inch and be secured together at 10 inch (254 mm) maximum intervals.
9.5 Doors and covers
9.5.1 A door more than 48 inches (1.2 m) long on the hinged side shall have one of the following:
a) A two-point or three-point latch operated by a single knob or handle; or
b) Two or more snap latches or captive screws involving a simple one-fourth or one-half turn; or
Exception: Multi-turn captive screws, having head diameter and grip to permit closing by hand, are not prohibited from being used in place of the captive screw involving a simple one-fourth or one-half turn.
c) One knob-operated latch and one snap latch or captive screw.
9.5.2 A door giving access to a fuse or any portion of a circuit breaker other than the operating handle shall shut closely against a 1/4-inch (6.4-mm) rabbet or that which has been determined to be the equivalent as illustrated in Figure 9.2.
9.5.4 To determine whether a flanged cover complies with the requirement in 9.5.3 regarding width of flange, the distance between the flat portion of the cover — clear of forming radii, beads, draws, and the like — and a straight edge placed anywhere across any two flanges at any point is to be measured.
9.5.5 A flange on a door shall:
a) Fit closely with the outside wall of the box proper in accordance with Table 9.3;
b) Have a width in accordance with Table 9.3;
c) Be one of the constructions illustrated in Figure 9.3, unless the construction has been evaluated and determined to comply with the requirements for the application; and
d) Where a telescoping cover meets the cabinet box of a surface-mounted enclosure, overlap all edges in accordance with Table 9.3.
Exception: A construction involving a gasketed joint that provides the intended tight fit shall be investigated to determine whether it meets the requirements for the application.
9.5.6 Figure 9.4 illustrates the method of determining the amount of overlap between a flat cover and a flanged box wall and the amount of overlap at a corner or box seam. When the radius of the flange bend is small, the flange width and overlap are considered to be Wi or W2, depending upon the actual construction, and shall be at least 1/2 inch (12.7 mm). When the radius of the flange bend is excessive or if the flat sheet is on the inside of the flange, the overlap, W3 or W4, is to be measured over only that portion where the two pieces of metal are actually in contact with each other, and shall be at least 1/2 inch.