UL 758:2022 pdf free download – STANDARD FOR SAFETY Appliance Wiring Material.
Compliance of the DC conductor resistance shall be determined in accordance with DC Conductor Resistance, Section 220, of UL 1581. For braided conductors, the following formula shall be used to calculate the DC resistance (DCR):
DCR = Resistance of one strand/[cos (braid angle)] X (number of ends) X (number of carriers)
Exception: The DC conductor resistance of tinsel conductor and magnet wire conductor shall not exceed the maximum value indicated on the tag, reel, or carton [see Exception 5 to 5 1.2(d)].
a ©IEC This material is reproduced from IEC 60228 with permission of the American National Standards Institute (ANSI) on behalf of the International Electrotechnical Commission. All rights reserved.
5.6.2 For conductors having a conductivity other than 100 percent as noted in Table 5.3, the maximum resistance is to be determined by multiplying the maximum resistance for uncoated copper by the ratio of 100 percent IACS (International Annealed Copper Standard) to the percent conductivity applicable to the conductor under consideration. For example, to determine the maximum resistance of a 12 AWG (6530 cmil or 3.31 mm2) solid 40-percent-conductivity copper-clad steel conductor:
a) R[12 AWG copper-clad steel at 20°C (68°F)] = R(12 AWG copper at 20°C) X 100/40 = R(12 AWG copper at 20°C or 68° F) X 2.5.
b) R[12 AWG copper at 20°C (68°F)] = 1.62 ohms/i 000 feet or 5.31 ohms/kilometer.
c) R[1 2 AWG copper-clad at 20°C (68° F)] = 1.62 X 2.5 = 4.05 ohms/I 000 feet or 5.31 X 2.5 = 13.28
ohms-kilometer.
5.6.3 Special alloy copper conductors having a conductivity of not less than 55 percent of 100 percent IACS (International Annealed Copper Standard) copper are not prohibited from being used when the finished wire or cable is suitable for the use, and when the cross section of the conductor is sufficient to give it a conductivity of not less than 55 percent of the 100 percent IACS (International Annealed Copper Standard) conductor and the tag is marked to indicate its nominal AWG size.
5.7 Stranding
5.7.1 Stranded conductors shall use a method of stranding that complies with the requirements in 5.7.2 —
5.7.8.
5.7.2 Conductors of intermediate nominal area shall comply with the requirement for the length of lay of the next smaller conductor as shown in Maximum lay of single-bunch, bunch stranded copper, copper alloy, copper-clad steel, copper-clad aluminum, and aluminum conductors, Table 5.9. The American Wire Gauge (AWG) sizes shown in Table 5.9 represent conductors of intermediate nominal area.
5.7.3 Metric-sized conductors of intermediate nominal area shall comply with the requirement for the length of lay of the next larger AWG size (smaller conductor) as shown in Table 5.9.
5.7.4 The individual wires used in making up a stranded conductor are usually drawn to the same diameter, which is not required to be the diameter of any AWG or other standard gauge number. The individual wires of a concentric-lay-stranded conductor are not required to be all of the same diameter.
5.7.5 A 19-wire combination round-wire unilay-stranded conductor of soft-annealed copper or an aluminum alloy indicated in this section shall be round and shall consist of:
a) A straight central wire,
b) An inner layer of six wires of the same diameter as the central wire with the six wires having identical lengths of lay, and
c) An outer layer consisting of six wires of the same diameter as the central wire alternated with six smaller wires having a diameter of 0.732 times the diameter of the central wire and with all twelve wires of the outer layer having the same length of lay and direction of lay as the six wires of the inner layer (see Nominal strand and conductor dimensions for 19-wire combination round-wire unilay-stranded copper conductors, Table 20.6 of UL 1581).