UL 50-2020 pdf free download.Enclosures for Electrical Equipment, Non-Environmental Considerations.
6.3 Openings
6.3.1 General
6 3.1.1 Other than as covered in Clause 6.3.1.2, openings provided in any enclosure type shall comply with the applicable tests in Annex B. Ref. No. 15, with these openings unfilled.
6.31.2 Openings in accordance with Clauses 3_4, and shall be appropriately filled to maintain the environmental integrity of the enclosure.
6.3.2 Equipment openings
6.3.2.1 Enclosures may be provided with openings that are intended to be closed by field installed equipment (such as pushbutton switches, door latches. etc.) if these enclosures are marked in accordance with Clause 77.
6.3.2.2 Openings that comply with Table 1 do not require the enclosures to be marked in accordance with Clause LZ.
6.3.3 Ventilation
6.3.3.1 Type 1, 2, 3R, and 3RX enclosures may be ventilated.
6.3.4 Mounting openings
6.3.4.1 For Type 1. 2. 3R. 3RX. or S enclosures, mounting means may be provided internal to the equipment cavity if the mounting openings comply with Table 2.
6.3.4.2 If mounting openings other than as noted in Table 2 are provided in Type 1, 2, 3R, 3RX, or 5 enclosures, instructions shall be included with the enclosure that indicate how to maintain the environmental integrity of the enclosure when mounted.
6.3.4.3 Mounting openings for enclosures constructed from a polymeric material shall additionally
comply with Clause Mounting openings requirements for enclosure Types 3, 3X, 3S, 3SX. 4, 4X, 6,
6P,12. 12K, and 13 are in Clause 7.3.4 of Annex B, Ref. No. 15.
6.3.5 Breakouts, knockouts and conduit openings
6.3.5.1 All breakouts. knockouts, and conduit openings shall comply with Clause jJ.Q.
6.3.5.2 A Type 12 enclosure shall not contain breakouts or knockouts but may have conduit openings if these openings comply with Clause BjQ.
6.3.6 Additional openings
6.3.6.1 A Type 1 enclosure may be provided with no more than four additional openings for the escape of air or for the drainage of paint during the painting process and the like. The size of these openings shall be no larger than two 3.2 by 3.2 mm (1/8 by 1/8 inch) openings and two 6.4 by 6.4 mm (1/4 by 1/4 inch) openings for enclosures not more than 457 mm (18 inches) long or wide in which the largest surface does not exceed 87.100 mm2 (135 in2). In a larger enclosure, an opening shall not be larger than 6.4 by 6.4 mm (1/4 by 1/4 inch).UL 50 pdf download.