UL 83-2017 pdf download – Thermoplastic-Insulated Wires and Cables.
4.1.6 Diameter and cross-sectional area 4.1.6.1 The nominal diameters of solid and stranded conductors are shown in Tables 4 – 9. There are no diameter requirements for conductor classes not referenced in Tables 4 – 9. See Clause 5.2 for conductor resistance requirements. The minimum diameter for stranded conductors is 98 percent of the nominal. The maximum diameter is 101 percent of the nominal. The diameter shall be determined in accordance with the test, Conductor diameter, in UL 2556, CSA C22.2 No. 2556, or NMX-J-066-ANCE. 4.1.6.2 Conductor sizes in mm 2 (AWG/kcmil) covered by this Standard are shown in Table 4. The nominal cross-sectional area of a conductor identified in Table 4 is not a requirement. 4.1.7 Joints 4.1.7.1 A joint (butt splice) where allowed shall be made before or after insulating and prior to further processing. Where joints (butt splices) are made after insulating, the insulation applied over the joint shall be of the same insulation material used throughout the length of the conductor, or of another insulating material that meets or exceeds the electrical, physical, and mechanical requirements of this Standard for the original insulating material. 4.1.7.2 A joint in a solid conductor or in one of the individual wires of a stranded conductor shall neither increase the diameter nor materially decrease the strength of the conductor or the individual wire. Not more than one of the wires in a stranded conductor of 19 wires or less, nor more than one of the wires in any given layer in a stranded conductor of more than 19 wires, shall be joined in any 0.3 m (1 ft) of conductor. 4.1.7.3 In a rope-lay-stranded conductor, which consists of a central core surrounded by one or more layers of stranded members (primary groups), each member shall be considered equivalent to a solid wire, and as such, shall be spliced as a unit. These joints shall not be any closer together than 2 lay lengths.