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By Mike Holt for EC&M Magazine
Q1. Can a single AFCI protected circuit be used to supply receptacle and lighting outlets in more than one bedroom?
A. The NEC specifies that all 15 or 20A, 120V branch circuits that supply outlets in dwelling unit bedrooms must be protected by a listed AFCI device [210.12], but this rule does not require a separate circuit for each bedroom. Since the NEC doesn't limit the number of receptacle and lighting outlets on a general-purpose branch circuit in a dwelling unit, you are fine.
Although there's no limit on the number of lighting and/or receptacle outlets on dwelling general-purpose branch circuits, the NEC does require a minimum number of circuits to be installed for general-purpose receptacles and lighting outlets [210.11(A)]. In addition, the receptacle and lighting loads must be evenly distributed among the required circuits [210.11(B)].
Q3. What rules apply to wiring located near carnival games that use water?
A. Attractions that utilize water, such as “bumper boats,” “dunking tanks,” and “duck ponds” where electric motors are used to circulate water in a tank in which guests may come in direct contact must be installed in accordance with Article 680 Swimming Pools, Fountains, and Similar Installations [525.3(D)].
But your question was about wiring located near the water game. Currently there are no requirements, such as maintaining minimum distance between receptacles and the water or GFCI protection of receptacles located outlets within 10 feet of the water.
Q4. Can I use two sets of parallel 3/0 THHN conductors in one raceway to supply a 400A, 120/240V feeder that has a continuous load of 320A?
A. The ampacity of 3/0 THHN is 225A at 90C [Table 310.16], based on bundling of no more than 3 current-carrying conductors. Since the raceway will contain a minimum of four and possibly six current-carrying conductors (depending on if the neutral is considered current carrying [310.15(B)(4)]), the conductor ampacity at 90C must be adjusted by a factor of 0.80.
Conductor Ampacity = Table Ampacity at 90C x Bundle Adjustment Factor
Conductor Ampacity = 225A x 0.80
Conductor Ampacity = 180A
The ampacity of the parallel set = 180A x 2 parallel sets = 360A
The minimum feeder conductor size, before any adjustment, must have an ampacity of not less than 125 percent of the continuous load [215.2(A)(1)] and the conductors must have overcurrent protection in accordance with 240.4(B), which is the next size up rule.
In this case, the conductors must have an ampacity of no less than 400A before ampacity adjustment [215.2(A)(1) (320A load x 1.25 = 400A before adjustment, a parallel set of 3/0 has an ampacity of 225A x 2 sets = 450A before derating), and they (360A after derating) are permitted to be protected by a 400A protection device [240.4(B)].
Q5. Does the Code restrict the wiring methods that can be used in a church sanctuary?
A. Article 518 covers all buildings or portions of buildings or structures designed or intended for the gathering together of 100 or more persons for deliberation, worship, or entertainment. That being the case, the following requirements contained in 518.4 applies:
(A) Spaces With Fire-Rated Construction. In the fire-rated portions of a building used for assembly occupancy, only metal raceways, nonmetallic conduits encased in not less than 2 in. of concrete, or Types MC and AC cables containing an insulated equipment grounding (bonding) conductor are permitted.
Exception: Wiring methods for the following systems are permitted within fire-rated construction in accordance with:
(a) Sound Systems—Article 640
(b) Communications Systems—Article 800
(c) ‑Class 2 and Class 3 Remote-Control and Signaling Circuits—Article 725
(d) Fire Alarm Circuits—Article 760
(B) Spaces With Nonfire-Rated Construction. In addition to 518.4(A) wiring methods, Type NM cable, Type AC cable, electrical nonmetallic tubing, and rigid nonmetallic conduit can be installed in those portions of an assembly occupancy building that aren't of fire-rated construction.
(C) Spaces With Finish Ratings. Electrical nonmetallic tubing and rigid nonmetallic conduit can be installed in club rooms, conference and meeting rooms in hotels or motels, courtrooms, dining facilities, restaurants, mortuary chapels, museums, libraries, and places of religious worship where:
(1) Electrical nonmetallic tubing or rigid nonmetallic conduit is installed concealed within walls, floors, or ceilings that provide a thermal barrier with not less than a 15-minute finish rating.
(2) Electrical nonmetallic tubing or rigid nonmetallic conduit is installed above suspended ceilings where the ceilings provide a thermal barrier not with less than a 15-minute finish rating.
Note: Electrical nonmetallic tubing and rigid nonmetallic conduit aren't permitted in dropped/suspended ceiling spaces used for environmental air [300.22(C].
| NEC Exam Practice Questions Textbook |
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The NEC Exam Practice Questions Book contains 2,400 questions from the National Electrical Code . There are 12 review quizzes of 100 questions each that are in code order and take you step-by-step through each of the 9 chapters of the National Electrical Code . The 12 practice quizzes of 50 questions each follow the NEC Review quizzes, but are presented in random order and contain questions different than those in the review quizzes.
In addition, this book contains 12 challenge quizzes of 50 questions each that cover all 9 chapters of the National Electrical Code . The questions in the challenge quizzes do not follow the chapters of the Code book as the other quizzes do, they are also organized in a random manner, and you might find them harder to answer. Scores for the first few challenge quizzes might be somewhat lower than you would like to see. But, as you go through this book and take the review and practice quizzes, you'll learn a great deal and gain a better understanding of the material. This improved knowledge and understanding will help you improve on the challenge quizzes as you go. Product
Code: 05PQ
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Illustrations:
Price:
$40.00 each
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