UL-48:2011 pdf free download – STANDARD FOR SAFETY Electric Signs.
4.2.4.2 Grounding (bonding) dead metal parts to the equipment grounding means
4.2.4.2.1 All parts of a sign required to be grounded shall be conductively connected to the grounding terminal, lead, or pin of an attachment plug.
4.2.4.2.2 Bonding shall be accomplished by positive metal-to-metal contact of parts such as machine screw connections, rivets, bolts, soldering, or welding; or by a minimum 14 AWG (2.1 mm2) copper or copper alloy bonding conductor.
4.2.4.2.3 Bonding may also be accomplished by a thread cutting screw that complies with the self threading screw torque test of 5.20.
4.2.4.2.4 A bonding means shall not be compromised during component servicing.
4.2.4.2.5 Liquid-tight flexible metal conduit and flexible metal conduit are able to be used as a bonding means when they:
a) Do not exceed 30 m (100 ft) in total accumulative length when enclosing wiring connected to secondary circuits operating over 1000 V; or
b) Do not exceed 1 .8 m (6 ft) in total accumulated length when enclosing wiring connected to the branch circuit supply; and
c) Are used with grounding-type fittings rated or determined to be capable of being used for the intended purpose.
4.2.4.2.6 When conduit is used as a bonding means, an additional bonding conductor connecting the same parts shall not be provided.
4.2.4.2.7 Bonding conductors shall be installed separately and remotely from non-metallic conduit housing secondary circuit conductors. It shall be spaced at a minimum of 38.1 mm (1.50 in) from the conduit when the secondary circuit operates at 100 Hz or less or 44.5 mm (1.75 in) when the circuit operates at above 100 Hz.
4.2.4.3 Equipment grounding means
4.2.4.3.1 General
4.2.4.3.1.1 An equipment grounding terminal or lead shall be provided within 152 mm (6 in) of the supply connection opening and shall not be removed during normal maintenance and servicing.
4.2.4.3.1.2 The grounding means shall be in the same location as the supply connection means and shall consist of a grounding conductor lead, a terminal connector, a wire binding screw, or the equivalent, and shall not be used for any other purpose.
4.2.4.3.1.3 A grounding connection wire binding screw or stud, or grounding lead shall be provided with a star washer or other fastening means that will penetrate a non-conductive coating such as paint.
4.2.4.3.1 .4 A neutral (grounded) conductor shall not be connected to any grounding or bonding terminal or lead.
4.2.4.3.2 Terminal
4.2.4.3.2.1 A grounding terminal shall be a pressure wire terminal, wire binding screw or wire binding stud. A pressure wire terminal shall comply with the requirements in the Standard for Equipment Wiring Terminals for Use with Aluminum and/or Copper Conductors, UL 486E, and be rated for the size and number of conductors used. A wire binding screw and stud shall comply with the requirements in this section.
4.2.4.3.2.2 A pressure wire connector provided for connection of an equipment-grounding conductor in the field shall be prevented from rotating by means other than friction between the terminal and mounting surface.
4.2.4.3.2.3 A wire binding screw or stud provided for grounding shall:
a) Be limited to terminating a single size 10-, 12-, or 14-AWG (5.3-, 3.3-, or 2.1-mm2)
conductor;
b) Comply with Table 4.13;
c) Be a machine or thread-cutting screw and have a cupped washer or the area around the screw or stud shall be provided with two raised areas in accordance with Figure 4.5. Other
means of conductor captivation shall comply with the applicable requirements in the Standard for Equipment Wiring Terminals for Use with Aluminum and/or Copper Conductors, UL 486E.