An enclosure that contains a device(s), or supports a fixture(s) or other equipment can be supported by the entering raceways when all of the following conditions are met: 1) the enclosure does not exceed 100 cubic inches in size; 2) the enclosure has threaded entries or hubs identified for the purpose; 3) the enclosure is supported by two or more conduits threaded wrenchtight into the enclosure or hubs; and, 4) each conduit is secured within 18 inches of the enclosure. Last month’s In Focus explained that an enclosure not containing a device or supporting a fixture (or other equipment) may be supported by two or more entering raceways where certain conditions are met. All of the conditions are the same except the distance between the enclosure and the support. While enclosures not containing devices or fixtures must be supported within 36 inches, enclosures containing devices or fixtures must be supported within 18 inches, unless meeting the requirements in Exception No. 2.
Care should be taken when modifying existing installations. A simple job of installing a light fixture (luminaire) could violate enclosure support requirements. For example: a single-gang, weatherproof junction box, containing no light fixture, was previously installed between two block walls. The enclosure is supported with two rigid metal conduits threaded wrenchtight into each end. Each conduit has a threaded coupling located 24 inches from the enclosure. Since the enclosure was not supported, each conduit was secured within 3 feet of the enclosure.
This original installation was installed according to Code, but now the owner wants a light fixture added to that enclosure. Adding a light fixture without supporting the enclosure or changing the conduit supports will create a violation.
To keep this from happening, a support can be added to each conduit within 18 inches of the enclosure.
Note... if the installation in Figure 3 met the specifications of 370-23(f) Exception No. 2, installing a light fixture would not cause a violation. One pertinent detail, common to all these drawings, is that each conduit has a threaded coupling located approximately 24 inches from the enclosure. Exception No. 2’s first sentence states that the supporting conduit must be unbroken. Therefore, because of the broken lengths of conduit, exception No. 2 is not applicable. Next month’s In Focus will present a detailed discussion of this exception.
Section 370-23(e) stipulates that under certain conditions, an enclosure containing no devices, or supporting no fixtures (or other equipment) can be supported by the entering raceways. This brings up a question—if the enclosure in Figure 2 is a junction box, are the wire connectors (wirenuts) considered devices? Article 100 defines a device as a unit of an electrical system, which carries but does not use electric energy. According to this definition, a wirenut could be considered a device. A proposal was submitted, and thus far accepted, for the 2002 NEC that clarifies this issue. (ROP 9-29) For the purpose of Section 370-23(e), splicing devices (wirenuts or wire connectors) are not considered devices.
Raceways supporting an enclosure that contains a device(s) or supports a fixture(s) or other equipment must be secured within 18 inches of the enclosure, regardless of where the raceway entries are located. Last month’s In Focus explained that raceways entering on the same side of an enclosure not containing a device or supporting a fixture (or other equipment) must be secured within 18 inches of the enclosure. Section 370-23(e) decreases the raceway support distance (from 36 to 18 inches) if the raceways enter on the same side. Section 370-23(f)’s support distance remains the same (18 inches), even if the raceways enter on the same side.
With all this discussion on enclosures being supported by the entering conduits, remember that more than one provision can be employed to support an enclosure. For example, just because an enclosure is supported by entering raceways, doesn’t mean that the enclosure itself can’t be supported. Enclosures within the scope of Article 370 shall be supported in accordance with one or more of the provisions in Section 370-23(a) through (h). [370-23]
370-23(f) Exception No. 1
Section 370-23(f) Exception No. 1 is similar to the exception in 370-23(e) discussed in last month’s In Focus. Both exceptions pertain to support requirements for conduit bodies (condulets). Section 370-23(e) Exception provides requirements for conduit bodies not containing devices or supporting fixtures. This exception is for a conduit body that contains a device(s) or supports a fixture(s) or other equipment. It can be supported by either rigid metal or intermediate metal conduit, provided the conduit body is not larger than the largest trade size of the conduit. A conduit body constructed with only one conduit entry can also be supported by either of these conduit types.
Unlike enclosures that cannot exceed 100 cubic inches in size, any size conduit body can be supported with either rigid or intermediate metal conduit. Rigid nonmetallic conduit and electrical metallic tubing are not permitted as means of support. Since the exception does not change the support distance, each conduit must be supported within 18 inches of the enclosure.
In order to use this exception, the trade size of the conduit body must not exceed that of the largest entering conduit. For example, if the trade size of the supporting conduit is 1 inch, the conduit body’s trade size must not exceed 1 inch. An oversized conduit body is permitted if it is securely supported, or it meets all the specifications in Section 370-23(f).
Since the conduit body in Figure 6 supports a light fixture, it obviously contains splices. Are splices permitted within a conduit body? Yes, splices are permitted, if the cubic-inch capacity is durably and legibly marked on the conduit body by the manufacturer. [370-16(c)(2)] The cubic-inch volume for the conductors, calculated in accordance with Section 370-16(b), must not exceed the cubic-inch volume marked on the conduit body.
Next month’s In Focus, beginning with Section 370-23(f) Exception No. 2, will continue discussion of Article 370, Part B, Installation. Section 370-23(f) Exception No. 2 is an alternative method to support a box used for fixture support or a wiring enclosure within a fixture and used in lieu of a box.
Miller, owner of Lighthouse Educational Services and author of the Illustrated Guide to the National Electrical Code (Delmar),can be reached by phone at (615) 333-3336, or via e-mail at charles@charlesRmiller.com.