UL 1:2017-08 Flexible Metal Conduit.
1.1 These requirements cover flexible aluminum and steel conduit designed for use as metal raceway for
wires and cables in accordance with the National Electrical Code, NFPA 70.
2 Units of Measurement
2.1 Values stated without parentheses are the requirement. Values in parentheses are explanatory or approximate information.
2.2 Unless otherwise indicated, all voltage and current values mentioned in this standard are root-mean-square (rms).
3 Undated References
3.1.1 Any undated reference to a code or standard appearing in the requirements of this standard shall be interpreted as referring to the latest edition of that code or standard.
4 Strip Material
4.1.1 The strip material used in flexible steel conduit shall be carbon steel, shall have a tensile strength of at least 34,000 lbf/in2 (234.5 MPa) and shall be of uniform width and thickness throughout. All surfaces of the strip shall be free from scale and rust before application of the protective zinc coating specified in Section 10.
4.1.2 Compliance of conduit with the surface-cleanliness requirement in 4.1.1 is to be determined by visual inspection.
4.2.1 The strip from which flexible aluminum conduit is made shall have:
a) A tensile strength of at least 34,000 lbf/in2 (234.5 MPa) and
b) A copper content of 0.40 percent or less. The strip shall be of uniform width and thickness throughout.
8 Interior Surfaces
8.1 The interior surfaces of finished steel and aluminum conduit shall be free from burrs and sharp edges that can damage wiring.
8.2 Compliance of conduit with the requirement in 8.1 is to be determined by visual examination of the interior surfaces. A specimen of conduit approximately 1 ft (300 mm) in length is to be inspected by looking through it (first from one end then from the other) at an artificial light.
9 Conduit Diameters
9.1 Finished flexible steel and aluminum conduit in trade sizes 3/8 — 4 shall have an external diameter that is not smaller than indicated in the second column and not larger than indicated in the third column of Table 9.1 (dimensions in inches) or Table 9.2 (dimensions in millimeters) and shall have an internal diameter that is not smaller than indicated in the fourth column of Table 9.1 (dimensions in inches) or Table 9.2 (dimensions in millimeters). Finished flexible steel and aluminum conduit in the 3/8 — 2 trade sizes shall have an internal diameter that is not larger than indicated in the fifth column of Table 9.1 (dimensions in inches) or Table 9.2 (dimensions in millimeters).UL 1 pdf download.