UL-977:2012 pdf free download – STANDARD FOR SAFETY Fused Power-Circuit Devices.
15.8 Friction between surfaces is not acceptable as a means to prevent turning of uninsulated live parts. Turning may be prevented by the use of two screws or rivets:
a) By a connecting strap or clip fitted into an adjacent part; or
b) By some other equivalent method.
15.9 Where parts are held together by screws, a threaded part shall have not less than two full clean-cut conventional machine screw threads — if the screw passes entirely through the piece. If the screw does not pass entirely through the threaded part, it shall engage full, clean-cut conventional machine screw threads for a distance of not less than the diameter of the screw.
15.10 Aluminum conductors, insulated or uninsulated, used as internal wiring — such as for
interconnection between current-carrying parts or as motor windings — shall be terminated at each end by a method acceptable for the combination of metals involved at the connections point.
15.11 If a wire-binding screw construction, or a pressure wire connector is used as a terminating device, it shall be acceptable for use with aluminum under the conditions involved (for example, temperature, heat cycling, vibration).
16 Wiring Terminals
16.1 Terminals shall be so designed as to accommodate either bus bars or wire connectors acceptable for carrying the rated current of the switch. Unless the switch is specifically intended for the connection of bus bars (see 50.6), pressure wire connectors that will accommodate wire corresponding to the continuous ampere rating of the switch shall be available.
16.2 A pressure wire connector provided with or specified for use with a fused power-circuit device shall comply with the requirements in the Standard for Wire Connectors, UL 486A-486B or the Standard for Equipment Wiring Terminals for Use with Aluminum and/or Copper Conductors, UL 486E. See 50.7.
16.3 The tightening torque for a field-wiring terminal shall be as specified by the fused power-circuit device manufacturer and shall be marked as required in 50.14. The specified tightening torque shall not be less than 90 percent and not more than 100 percent of the value employed in the static heating test as specified in the Standard for Wire Connectors, UL 486A-486B or the Standard for Equipment Wiring Terminals for Use with Aluminum and/or Copper Conductors, UL 486E, for that wire size corresponding to the ampere rating of the fused power-circuit device. See 27.1.
Exception: Torque values may be less than 90 percent if the connector is investigated in accordance with UL 486A-486B or UL 486E, using the lesser assigned torque value.
16.4 The terminal connections shall be such that the connection of field-installed bus bars or cables will not cause overheating due to inductive effects.
16.5 A fused power-circuit device that is marked for service equipment use shall have a terminal for a grounded-service conductor even though it has no provision for a grounded-load conductor. If there is no provision for a grounded-load conductor, this terminal:
a) Shall accommodate a conductor of the same size as the main bonding jumper shown in Table 24.1;
b) Shall be bonded to the enclosure.