UL-1023:2017 pdf free download – STANDARD FOR SAFETY Household Burglar-Alarm System Units.
10.4.1 The thickness of sheet metal employed for the enclosure of a product shall be not less than that indicated in Table 10.2 or 10.3, whichever applies.
Exception: Sheet metal of lesser thickness may be employed if consideration being given to the shape, size, and function of the enclosure, it provides equivalent mechanical strength. See the Drop Test, Section 56, and the Mechanical Strength Tests for Enclosures, Section 59.
10.4.2 A sheet metal member to which a wiring system is to be connected in the field shall have a thickness of not less than 0.032 inch (0.81 mm) if of uncoated steel, 0.034 inch (0.86 mm) if of galvanized steel, and 0.045 inch (1.14 mm) if of nonferrous metal.
10.5 Nonmetallic
10.5.1 If nonmetallic material is used for an enclosure, it shall have a wall thickness of not less than 1/16 inch (1.6 mm).
10.5.2 Among the factors to be taken into consideration when determining the acceptability of a nonmetallic enclosure are:
a) The mechanical strength;
b) Resistance to impact;
c) Moisture-absorptive properties;
d) Flammability and resistance to ignition from electrical sources;
e) Dielectric strength, insulation resistance, and resistance to arc tracking; and
f) Resistance to distortion and creeping at temperatures to which the material may be subjected under any conditions of use.
All these factors are to be considered with respect to aging in accordance with the Tests on Polymeric Materials requirements (see Section 53). See the Drop Test, Section 56, and the Mechanical Strength Tests for Enclosures, Section 59.
10.6 Doors, covers, and guards
10.6.1 An enclosure cover shall be hinged, sliding, or similarly attached to prevent its being removed if:
a) It gives access to fuses or any other overcurrent protective device, the intended protective functioning of which requires renewal or
b) It is necessary to open the cover in connection with the intended operation of the unit.
Exception: An enclosure cover need not comply with this requirement if its position is supervised by a tamper contact that is connected in the closed protective circuit.
10.6.2 Cabinet locks or equivalent means requiring a tool or key shall be used for all enclosures if access is not required for intended operation of the product.
10.7 Screens and expanded metal
10.7.1 Perforated sheet steel and sheet steel employed for expanded metal mesh shall be:
a) At least 0.042 inch (1.07 mm) thick [0.045 inch (1.17 mm) if zinc coated] if the mesh openings or perforations are 1/2 square inch (323 mm2) or less in area and
b) At least 0.080 inch (2.03 mm) thick [0.084 inch (2.13 mm) if zinc coated] for larger openings. The largest dimension shall not exceed 4 inches (102 mm).
Exception: If the indentation of a guard or the enclosure will not alter the clearance between uninsulated live parts and grounded metal so as to impair performance or reduce spacings below the minimum required values (see Spacings, General, Section 27), 0.020 inch (0.53 mm) expanded metal mesh or perforated sheet metal [0.023 inch (0.58 mm) if zinc coated] may be employed, provided that.