To play this game, you need a sharp eye, a quick mind and a 2014 National Electrical Code book.
(Fill-in-the-blank questions are looking for the exact word(s) used in the NEC.)
1) Messenger-supported wiring shall not be used in ________ or where subject to physical damage.
- A) Marinas
- B) Hoistways
- C) Wet locations
- D) Hazardous locations
2) For each yoke or strap containing one or more devices or equipment, a ________ volume allowance in accordance with Table 314.16(B) shall be made for each yoke or strap based on the largest conductor connected to a device(s) or equipment supported by that yoke or strap.
- A) Single
- B) Double
- C) Triple
- D) Quadruple
3) Type MC cable shall be supported and secured by staples, cable ties, ________, hangers, or similar fittings or other approved means designed and installed so as not to damage the cable.
- A) Yarn
- B) Strut
- C) Straps
- D) Cable trays
4) Receptacles mounted to and supported by a cover shall be held rigidly against the cover by more than one screw or shall be a(n) ________ or box cover listed and identified for securing by a single screw.
- A) Securing clamp
- B) Grounded cover
- C) Device assembly
- D) Integral device cover
5) __________, together with their mounting and conductor attachments, where used as supports for wires, single-conductor cables, or busbars, shall be capable of safely withstanding the maximum magnetic forces that would prevail if two or more conductors of a circuit were subjected to short-circuit current.
- A) Clamps
- B) Insulators
- C) Bridle rings
- D) Messenger wires
6) Open conductors shall be supported on _______ or porcelain knobs, racks, brackets, or strain insulators.
- A) Glass
- B) Plastic
- C) Ceramic
- D) Stainless steel
7) The ________ shall be of adequate strength or be supported by braces or guys to withstand safely the strain imposed by the service-drop or overhead service conductors.
- A) Guy wire
- B) Weatherhead
- C) Service mast
- D) Meter enclosure
8) At what distance must supports for the conductors inside an MC Cable be installed in a vertical installation if the ungrounded conductors are 250 kcmil copper?
- A) 6 feet
- B) 10 feet
- C) 60 feet
- D) None of the above
9) Can an electrical equipment enclosure above deck level on a pier in a marina be supported solely by the conduit(s)?
- A) Yes
- B) No
10) Is all electrical equipment prohibited from being supported by trees or other vegetation?
- A) Yes
- B) No
1) B, hoistways.
396.12 prohibits the use of messenger-supported wiring in hoistways. In hazardous locations, 396.10(C) allows the
use of messenger-supported wiring if specifically permitted by other articles of the NEC.
2) B, double. 314.16(B)(4) requires a double volume allowance for device or equipment fill. For example, if a switch on a yoke is connected with 14 AWG conductors, the switch volume allowance would be 4 cubic inches. To find that value, go to Table 314.16(B) and find the value for 14 AWG conductors. The value is 2.00 cubic inches, so multiplying that value by 2 gives you the 4.00 cubic inches for the installed device.
3) C, straps. Securing and supporting methods for MC Cable are found in 330.30(A). Like many cable wiring methods, there are a variety of methods available to support MC Cable. While the NEC does not require these support methods to be listed, it should be noted that there are listed cable ties available that are evaluated for strength and resistance to ultraviolet light.
4) C, device assembly. This requirement is found in 406.5(C), Receptacles Mounted on Covers. Ensuring that the receptacle is firmly attached to the cover prevents the receptacle from “floating” in the box and potentially creating poor connections with the inserted plugs.
5) B, Insulators. This requirement is found in 110.36. Since this language is located in Part III of Article 110, it applies to installations over 600 volts.
6) A, glass. 225.12 has requirements for open-conductor supports for outdoor feeder and branch circuits. 225.14 has requirements for open-conductor spacing for circuits with nominal voltages of 1000 volts or less.
7) C, service mast. This requirement is found in 230.28(A). The mechanical stress from the weight of the service conductors can easily pull the service mast away from the building if it is of inadequate strength or support. The local serving electric utility will generally provide requirements for the type of service mast and any necessary braces or guys.
8) D, none of the above. NEC 300.19(A) gives intervals for supporting conductors in vertical raceways, but MC Cable is not a raceway. The definition of “raceway” and the wiring method definitions in the appropriate articles were updated in the 2014 NEC to make it clear which wiring methods are raceways; MC Cable is not one of those, therefore 300.19(A) does not apply. The requirements in 330.30 for securing and supporting MC Cable apply to the entire cable, not the conductors inside.
9) B, no. 555.10(A) requires that electrical equipment enclosures installed on piers above deck level be securely and substantially supported by structural members, independent of any conduit connected to them.
10) B, no. Although 230.10 and 225.26 prohibit the use of vegetation such as trees for support of overhead service conductors and overhead conductor spans for outdoor branch circuits and feeders, other electrical equipment is allowed to be supported by vegetation. 410.36(G) specifically permits outdoor luminaires and associated equipment to be supported by trees, and there are many other installations that are not prohibited from being supported by trees or other vegetation.
For temporary installations, 590.4(J) prohibits the use of vegetation for support of overhead spans of branch circuits or feeders, but there is an exception for holiday lighting that states: “For holiday lighting in accordance with 590.3(B), where the conductors or cables are arranged with strain relief devices, tension take-up devices, or other approved means to avoid damage from the movement of the live vegetation, trees shall be permitted to be used for support of overhead spans of branch-circuit conductors or cables.”