Guide · Outdoor electrical

In-use cover vs. weatherproof cover: what NEC 406.9 actually requires

Every outdoor receptacle needs a cover, but not every cover satisfies the code. Here is the difference between a flat weatherproof cover and an extra-duty while-in-use cover, and how to know which one the inspector expects.

Damp location or wet location?

The NEC splits outdoor locations in two. A damp location is protected from direct weather but exposed to moisture: a covered porch, an open carport, under a wide eave. A wet location is anything else outdoors where rain can reach the device, plus anywhere subject to saturation or washing down. The location, not the device, decides the cover.

What 406.9 says

• 406.9(A) Damp locations. A receptacle in a damp location needs an enclosure that is weatherproof when the receptacle is covered — that is, when nothing is plugged in and the lid is closed. A self-closing flat cover meets this.
• 406.9(B)(1) Wet locations. A 15- or 20-amp, 125- or 250-volt receptacle in a wet location needs an enclosure that stays weatherproof whether or not a plug is inserted. That is a while-in-use (in-use, “bubble”) cover, and the code adds that outdoor covers must be listed and marked Extra Duty.
• Other receptacles (larger amperages, or where the attached equipment is not attended while in use) also need an enclosure that is weatherproof with the plug inserted — again an in-use cover.

What “Extra Duty” means

Extra Duty is an impact and UV rating under UL 514D. An extra-duty cover survives a heavier impact test at low temperature than a standard-duty cover, so it holds up to ladders, carts and cold winters. Since the 2011 NEC, outdoor in-use covers for 15- and 20-amp receptacles must carry the Extra Duty marking; a standard-duty in-use cover will fail inspection on new work. Every Sealproof while-in-use cover is Extra Duty rated. The standard and shallow covers are cULus Listed; the one-gang slim covers are CSA certified (file 174008).

Choosing the cover

Match the box

Covers are gang-specific. A one-gang box takes a one-gang cover (the 18-in-1 series), a two-gang box takes the two-gang 45-in-1 cover. The multi-configuration plate adapts to duplex, decorator/GFCI, single and round receptacles in either orientation, so one SKU covers most jobs.

Plastic or metal

Polycarbonate covers are the default: UV-stabilised, corrosion-free and clear or coloured to match the wall. Where a specification calls for a metal enclosure or the cover will take real abuse, use the extra-duty metal in-use cover.

Depth

Standard-depth covers accept transformer plugs and right-angle cords. Where clearance is tight, the extra-duty shallow cover keeps the profile low while staying Extra Duty rated.

Colour and lock

Clear, gray, white, black and bronze covers are stocked. Every cover has a hasp for a small padlock, useful on rental properties and commercial exteriors.

Installation checklist

1. Confirm the receptacle is GFCI-protected (NEC 210.8 applies to virtually all outdoor 15/20-amp receptacles).
2. Fit the gasket between box and cover; replace a brittle gasket rather than reusing it.
3. Plug unused box hubs with threaded closure plugs.
4. Mount the cover so the cord opening faces down.
5. Check that the lid closes fully with the cord in place; use a shallow or deep cover as needed.

Sealproof parts for this job

Published by Superflex Ltd., manufacturer of Sealproof® and Rollerflex® products in Elizabeth, New Jersey since 1981. This guide is general information for installers and specifiers; always follow the current edition of the NEC as adopted in your jurisdiction, the product listing and the manufacturer instructions.