[Outlet Boxes and Fittings] Metallic Outlet Boxes, QCIT

See General Information for Outlet Boxes and Fittings



This category covers metallic mud rings, flush device boxes, conduit bodies, conduit boxes, floor boxes, outlet boxes, outlet box hoods, special-purpose boxes, extension rings, covers, and cover plates for flush-mounted wiring devices, intended for installation in accordance with Article 314 of ANSI/NFPA 70, "National Electrical Code" (NEC). These products are also intended for installation and use in accordance with the following information.


A mud ring positions a flush-mounted wiring device flush with the finished wall surface. Mud rings may be provided with either a fixed or adjustable depth sleeve.


Extension rings are suitable for extending properly secured flush- or surface-mounted boxes. One or more extensions may be used. An extension ring is intended to increase the box depth, volume, or both.


Conduit bodies that are provided with a volume marking can enclose splices, taps or devices. Conduit bodies that are not provided with a volume marking are covered under Conduit Fittings (DWTT). Conduit bodies certified for use with specific conduit body covers and conduit body covers certified for use with specific conduit bodies are covered under Conduit Bodies and Covers Certified for Use with Specified Equipment (QCKW).

Conduit bodies that have been investigated for a specific combination of conductors are marked, on the conduit body or on or within the unit container of the conduit body, with the maximum number and maximum size of the conductors for which they are intended. For other conductor sizes and combinations, the total cross-sectional area of the fill should not exceed the cross-sectional area of the conductors specified in the marking. The total cross-sectional area is determined using the following type of conductor:

a) Type THHN or T90 Nylon for a fitting for use with 1/2 or 3/4 (16 or 21) trade size conduit or tubing, and
b) Type XHHW or RW90 XLPE for a fitting for use with 1 - 4 (27 - 103) trade size tubing and for use with 1 - 6 (27 - 155) trade size conduit.


All boxes with concentric or eccentric knockouts have been investigated for bonding and are suitable for bonding without any additional bonding means around concentric (or eccentric) knockouts where used in circuits above or below 250 V, and may be marked as such.


Boxes may or may not be provided with clamps. When clamps are provided, the carton is marked to indicate the type of wiring system or combination of systems for which they have been tested. The clamps are marked with the following letters or combinations thereof to indicate that they are suitable for use with armored cable ("A"): flexible metal conduit - "F," nonmetallic-sheathed cable - "N," or flexible tubing (loom) - "T." Clamps suitable for Type MC metal-clad cable are marked "MCI" for metal-clad interlocking armored cable, "MCI-A" for metal-clad interlocking armor ground cable, "MCS" for metal-clad continuous smooth-sheath cable, and "MCC" for metal-clad continuous corrugated-sheath cable. If suitable for all seven types, the clamp is marked "ALL." Clamps suitable for nonmetallic-sheathed cable are also suitable for multiconductor underground feeder and branch circuit cable where used in dry locations.

Clamps have been tested for securing only one cable per clamp, except multiple section clamps are considered suitable for securing one cable under each section of the clamp, each cable entering a separate knockout.


Clamps for armored cable, flexible metal conduit, metal-clad interlocking armor ground cable, metal-clad continuous smooth-sheath cable, or metal-clad continuous corrugated-sheath cable are considered suitable for grounding where installed in accordance with the NEC.


A box, with or without a bracket or bar hanger, intended for support of a fixture/luminaire weighing 50 lbs or less is marked "FOR FIXTURE/LUMINAIRE SUPPORT" on the carton to indicate that the box is intended for fixture/luminaire support. A box, with or without a bracket or bar hanger, intended for support of a fixture/luminaire weighing more than 50 lbs is marked with the weight of the fixture/luminaire to be supported. Metallic device boxes and device plaster rings have not been investigated for support of a ceiling fixture/luminaire unless marked for use in ceilings, walls, and with the weight of the product to be supported. Metallic device boxes or metallic device boxes intended to be installed in an existing structure have been investigated for the support of utilization equipment weighing not more than 6 lbs.


Boxes with integral connectors for electrical metallic tubing or for unthreaded rigid metallic conduit are provided with a marking on the carton to indicate the specific type or types of wiring system for which the boxes have been tested.


A box, or a box with a bracket or bar hanger intended for support of a ceiling-suspended (paddle) fan weighing 35 lbs or less is marked "ACCEPTABLE FOR FAN SUPPORT" on the product. A box, or a box with a bracket or bar hanger intended for support of a ceiling-suspended (paddle) fan weighing more than 35 lbs but not more than 70 lbs is marked "ACCEPTABLE FOR FAN SUPPORT OF 70 LBS OR LESS" on the product. A box, or a box with a bracket or bar hanger intended for support of a ceiling-suspended (paddle) fan is acceptable for use with a fixture/luminaire when provided with the above fixture/luminaire-support markings.


All metal boxes, except aluminum alloy boxes, are provided with corrosion protection suitable for installation in concrete. Aluminum alloy boxes covered under this category are not considered acceptable for installation in concrete or cinder fill unless protected by asphalt paint or the equivalent. Boxes designated as "concrete tight" may have no means of support other than the concrete and often accommodate covers at top and bottom.


Floor boxes designed for floor installation as covered in the NEC are provided with covers and gaskets to exclude surface water and sweeping compounds that might be present in floor cleaning operations. Covers with gaskets may be shipped separately from the boxes. Both products are provided with installation instructions. Those boxes intended for installation in concrete floors are frequently provided with leveling screws, threaded hubs or both, and are provided with a marking on the carton to identify boxes of this type such as "Floor Box Cover," "Floor Box" or "Floor Box, Concrete Tight," as appropriate. Floor boxes may be provided with wiring devices. Refer to WET AND DAMP LOCATIONS below for clarifying information on the suitability of concrete-tight floor boxes not intended to be exposed to weather that are installed in concrete slabs or masonry.


Boxes and covers intended for use in wet locations as defined by the NEC are marked "Wet Location." Damp location boxes and covers are intended to be so located or equipped as to prevent water from entering or accumulating in the box and are marked "Damp Location." Boxes with threaded conduit hubs will normally prevent water from entering except for condensation within the box or connected conduit.

Box and device cover combinations, and flush device covers that provide protection from the weather only when the cover is closed, are marked "Wet Location Only When Cover Closed" and may be marked "Damp Location." Outlet box hoods intended for use in damp or wet locations are marked for each location and may be marked "Extra-Duty."

Floor boxes designated as "concrete tight" installed in concrete slabs or masonry are not considered to be in wet locations when the following conditions are met:

1. a vapor barrier is installed between the earth and a concrete slab or masonry (i.e., the concrete slab or masonry is not in direct contact with the earth),
2. the floor box is protected from exposure to weather within a building as defined by the NEC, and
3. the concrete slab or masonry above the vapor barrier is not subject to saturation by water or other liquids.


Boxes may be marked with the environmental Enclosure Type number (1, 2, 3, 3R, etc.) as described in Electrical Equipment for Use in Ordinary Locations (AALZ).

Boxes marked with Enclosure Type 3X or "Corrosion Protection" provide the same level of protection as Type 3 enclosures, and are provided with an additional level of corrosion protection for the enclosure.


One of the following product identities appears on the product:

    Extension Ring

    Flush Device Box

    Outlet Box

    Outlet Box and Cover

Other product identities may be used as shown in the individual certifications.


Outlet box assemblies that include certified outlet boxes and one or more of the following certified parts: wiring device, mud ring, cover plate, wet-location gasket and cover plate, wet-location gasket and outlet box hood, or other factory-assembled parts, are covered under Wiring Assemblies (QQYZ).


For additional information, see Electrical Equipment for Use in Ordinary Locations (AALZ).


The basic standards used to investigate products in this category are ANSI/UL 514A, "Metallic Outlet Boxes," and ANSI/UL 514D, "Cover Plates for Flush-Mounted Wiring Devices."


The Certification Mark of UL on the product, or the UL symbol on the product and the Certification Mark on the smallest unit container in which the product is packaged is the only method provided by UL to identify products manufactured under its Certification and Follow-Up Service. The Certification Mark for these products includes the UL symbol, the words "CERTIFIED" and "SAFETY," the geographic identifier(s), and a file number.

Alternate UL Mark

The Listing Mark of UL on the product, or the UL symbol on the product and the Listing Mark on the smallest unit container in which the product is packaged is the only method provided by UL to identify products manufactured under its Listing and Follow-Up Service. The Listing Mark for these products includes the UL symbol (as illustrated in the Introduction of this Directory) together with the word "LISTED," a control number, and one of the following product names: "Outlet Box," "Outlet Box and Cover," "Extension Ring," "Flush Device Box," or other appropriate product name as shown in the individual Listings.

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UL, in performing its functions in accordance with its objectives, does not assume or undertake to discharge any responsibility of the manufacturer or any other party. UL shall not incur any obligation or liability for any loss, expense or damages, including incidental or consequential damages, arising out of or in connection with the use, interpretation of, or reliance upon this Guide Information.

1900 Boxes4 Square Boxes4 SquaresAdjustable Mud RingsCover Plates, MetallicDog House BoxesExtension RingsFlush Device BoxesFour Square BoxesGarvin CoversGem BoxesGoof RingsIndustrial Raised CoversMud BoxesMud RingsOutlet Box CoversOutlet Box HoodsOutlet Boxes, MetallicPlaster RingsRaised Covers
Last Updated on 2018-07-09
QCIT.GuideInfo QCIT Active 20180709 20180709

The appearance of a company's name or product in this database does not in itself assure that products so identified have been manufactured under UL's Follow-Up Service. Only those products bearing the UL Mark should be considered to be Certified and covered under UL's Follow-Up Service. Always look for the Mark on the product.

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