UL 884:2016 pdf download

5.2 The resistance of the connection of a duct with a fitting shall be tested in accordance with theGrounding Continuity Test,Section 14.

5.3 A sheet metal screw shall not be used for the connection of an equipment grounding conductor.
6 Protective Coatings

6.1 Preset inserts and ducts

6.1.1 Each preset insert made of iron or steel and all surfaces of duct that are not specifically excepltedin 6.1.2 shall be protected against corrosion by one of the following coatings:

a) A coating of zinc (applied by any method) that complies with the test requirements in 15.1;
b) A metal coating other than zinc but at least as protective as the coating of zinc that is

mentioned in (a);

c) A system of organic paint or enamel that evaluation shows to be at least as protective as thecoating of zinc mentioned in (a); see 15.2.

d) A system of epoxy coating, which upon evaluation demonstrates the same level of protectionas the coating of zinc mentioned in (a); see 15.3.

6.1.2 In the case of zinc-coated sheet-steel duct (zinc applied by any method), a zinc coating is notrequired at any cut edge or at spot welds.

6.1.3 The edges of holes for preset insets are bare if the holes are cut after the duct is painted orenameled. Paint or enamel is to be added to the edges unless the inserts are made of a zinc-base alloy.

6.1.4 The zinc coating on the inside and outside of finished duct shall be of uniform quality throughoutand shall have a smooth and even appearance.Visual inspection shall determine whether duct complieswith this requirement.