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This photo shows an all-too-common installation mistake: An outdoor box supported by a single raceway. This particular installation is an obvious and clear violation of 314.23.
The third sentence in 314.23(F), which covers raceway-supported enclosures that are providing support for devices and/or fixtures, says "It (i.e., the box) shall be supported by two or more conduits threaded wrenchtight into the enclosure or hubs." The next sentence indicates that "Each conduit shall be supported within 450mm (18 in.) of the enclosure." Although the requirement given in the third sentence of 314.23(F) for raceway-support of an outlet box has been met, the rule presented by the second sentence — use of two conduits threaded into the box or hubs — has not.
It should be noted that raceway support of outlet, device, junction, and pull boxes has long been permitted by the NEC, but with certain restrictions. In addition, use of the raceway-supported box to provide support for devices and fixtures has also been acceptable for some time. In this photo, we see an outlet box-mounted incandescent flood light and a photoelectric switch that controls the light, which is specifically permitted by the Code, but only in accordance with the rules of 314.23(F).
The first sentence of part (F) in 314.23 states, "An enclosure that contains a device(s), other than splicing devices, or supports a luminaire(s), lampholder or other equipment and is supported by entering raceways shall not exceed 1,650 cm3 (100 in3) in size." This application meets that stipulation, but the wording used in that sentence actually recognizes the use of an outlet box to support more than one device and/or fixture, provided the box is not more than 100 in3. However, a certain amount of common sense must be exercised when applying this rule. Obviously, the number and size of devices and/or fixtures should be limited to ensure the box, which may be no more 100 in3 to satisfy the specific verbiage used in 314.23(F), is capable of actually providing support for the attached equipment. This is a different approach that the Code takes when dealing with ceiling and wall outlet boxes that support fixtures as covered in 314.27(A).
In part (A) of 314.27, the NEC requires that ceiling-mounted outlet boxes supporting fixtures "shall be designed for the purpose and shall be required to support a luminaire (fixture) weighing a minimum of 23 kg (50 lb)." For wall-mounted outlet boxes, the Code places the same mandate on the design of the box. As we have seen, for raceway-supported boxes that are providing support for devices and fixtures, there is no limitation on the number or size of the attached equipment, which essentially requires the installer and inspector to determine the "maximum" number and size of devices and fixtures.