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I have a knockout in an outdoor electrical panel that is above the uninsulated portion of the panel. I need to run 4/0 SER wire into the panel. According to NEC 312.2, I need a wet listed fitting when working above the uninsulated portion of the panel. However, I can only find weatherproof fittings for SE/SEU, but not SER.

Several web sites seem to recommend using standard dry-location clamps plus duct seal or caulk, but that doesn't seem to meet the requirements of 312.2.

What is the proper way of terminating SER at this location?

312.2 Damp and Wet Locations. In damp or wet locations, surface-type enclosures within the scope of this article shall be placed or equipped so as to prevent moisture or water from entering and accumulating within the cabinet or cutout box, and shall be mounted so there is at least 6-mm (1/4-in.) airspace between the enclosure and the wall or other supporting surface. Enclosures installed in wet locations shall be weatherproof. For enclosures in wet locations, raceways or cables entering above the level of uninsulated live parts shall use fittings listed for wet locations.

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I ended up buying SEU compression clamps and drilling out the rubber grommet with a round drill to fit SER. It feels wrong, and its certainly not listed for that use. But it seems to be the best option available, and in my limited testing it is weathertight.

  • How are you attaching the fitting to the top of the panel? – ThreePhaseEel Dec 30 '19 at 23:44
  • @ThreePhaseEel Through a standard knockout. The SEU clamps have a rubber O-ring as part of them to seal against the box. – David Pfeffer 21 hours ago

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