UL 797A:2017-01 Electrical Metallic Tubing一Aluminum and Stainless Steel.
1.1 These requirements cover aluminum and stainless steel electrical metallic tubing (EMT) and elbows in trade sizes 3/8 — 4 (12 — 103) for use as a metal raceway for the installation of wires and cables in accordance with the National Electrical Code. The values in parentheses are metric designators of tubing.
1 .2 Tubing provided with an exterior coating of zinc or a zinc-based, nonmetallic, or other alternate corrosion-resistant material and an interior coating of an organic or zinc material, is covered by the Standard for Electrical Metallic Tubing — Steel, UL 797.
2 Units of Measurement
2.1 Values stated without parentheses are the requirement. Values in parentheses are explanatory or approximate information.
3 References
3.1 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 Tube
4.1 Each tube shall be of an aluminum alloy or stainless steel containing no more than 0.40 percent copper. Other metal shall be evaluated.
4.2 Each tube shall have a circular cross section. All seams shall be thoroughly welded.
4.3 A welded seam shall be without any metal trimming, sharp edge or sharp projection.
5 Protective Coatings
5.1 Aluminum and stainless steel electrical metallic tubing does not require a protective coating.
Exception: Aluminum electrical metallic tubing intended for use in concrete, for direct burial, or for use in severely corrosive environments, shall be provided with a protective coating.
5.2 It is not prohibited for one or more protective coatings to be employed. When such protective coatings have not been evaluated as supplying corrosion resistance for the tube they shall be marked in accordance with 10.4.
5.3 Nonmetallic coatings shall be evaluated with respect to flame propagation, the fit of couplings, and electrical continuity with couplings.
6 Straight Tubing
6.1 The length of electrical metallic tubing shall not be greater than given in Table 6.1.UL 797A pdf download.