UL-758:2014 pdf free download – STANDARD FOR SAFETY Appliance Wiring Material.
5.7.7 A compressed-stranded conductor shall be a round conductor consisting of a central core wire surrounded by one or more layers of helically laid wires with either the direction of lay reversed in successive layers, or of unilay or unidirectional lay. The direction of lay of the outer layer shall be left-hand in all cases unless specifically noted on the tag markings. The strands of one or more layers are slightly compressed by rolling, drawing, or other means to change the originally round strands to various shapes that achieve filling of some of the spaces originally present between the strands.
5.7.8 Every stranded conductor other than a compact-stranded conductor or a single-bunch bunch-stranded conductor shall comply with the following:
a) The direction of lay of the strands, members, or ropes in a 6 AWG — 2000 kcmil conductor other than a combination unilay or compressed unilay or compressed unidirectional lay
conductor shall be reversed in successive layers. Rope-lay conductors with bunch-stranded or concentric-stranded members shall be either unidirectional or reversed. All unidirectional lays and the outer layer of reversed lays shall be in the left-hand direction unless specifically noted on the tag markings.
b) For a bunch-stranded member of a rope-lay-stranded conductor in which the members are formed into rope-stranded components that are then cabled into the final conductor, the length of lay of the individual members within each component shall not be more than 30 times the
outside diameter of one of those members.
c) For a concentric-stranded member of a rope-lay-stranded conductor, the length of lay of the individual strands in a member shall be 8 — 16 times the outside diameter of that layer. The
direction of lay of the strands in each member shall be reversed in successive layers of the member.
d) The length of lay of the strands in both layers of a 19-wire combination round-wire unilaystranded copper or aluminum conductor shall be 8 — 16 times the outside diameter of the
completed conductor. Otherwise, the length of lay of the strands in every layer of a concentric- lay-stranded or compressed-stranded conductor consisting of fewer than 37 strands shall be a maximum of:
1) 40 times the outside diameter of the conductor for 30 AWG or smaller conductors;
2) 30 times the outside diameter of the conductor for size 29 — 15 AWG conductors;
3) 20 times the outside diameter of the conductor for size 14 — 6 AWG conductors; and
4) 16 times the outside diameter of the conductor for 5 AWG and larger conductors.
e) The length of lay of the strands in the outer two layers of a concentric-lay-stranded
conductor consisting of 37 or more strands shall be 8 — 16 times the outside diameter of that layer.
f) The length of lay of the members or ropes in the outer layer of a rope-lay-stranded conductor shall be 8 — 16 times the outside diameter of that layer.
5.7.9 A composite conductor composed of six bare or metal-coated copper strands with one central steel strand may be accepted for internal wiring of electronic equipment where not subject to flexing.
5.7.10 A single conductor may consist of three bunch-stranded members laid parallel. The stranding within each member shall comply with the lay length requirements described in 5.7.2 and determined based on the size of each individual member.
5.8 Separator
5.8.1 The insulation shall be prevented, by the manufacturing process or by a separator constructed for the intended use, from penetrating between the strands of a stranded conductor for thermoset insulation.