NEC Special Occupancies & Equipment 3 — Questions and Answers
Question 1: NEC Article 503 covers Class III locations. What makes a location Class III?
- Presence of flammable gases
- Presence of combustible dusts
- Presence of easily ignitable fibers or flyings (Correct answer)
- Presence of explosive vapors
Correct answer: Presence of easily ignitable fibers or flyings
Class III locations are hazardous because of the presence of easily ignitable fibers or flyings, such as those found in textile mills.
Question 2: What NEC article governs electrical installations in theaters, audience areas of motion picture studios, and similar locations?
- Article 511
- Article 518
- Article 520 (Correct answer)
- Article 525
Correct answer: Article 520
NEC Article 520 covers electrical wiring and equipment installed in or about theaters, audience areas of motion picture studios, and similar locations.
Question 3: For swimming pools under NEC Article 680, what is the minimum required distance for overhead conductors (other than service drops) to clear the water's edge horizontally?
- 5 feet
- 10 feet
- 15 feet (Correct answer)
- 20 feet
Correct answer: 15 feet
NEC 680.8 requires overhead conductors (other than service drops) to maintain a minimum 15-foot horizontal clearance from the edge of a swimming pool.
Question 4: Under NEC Article 680, luminaires installed in the wall of a permanently installed swimming pool must be at least how far below the normal water level?
- 6 inches
- 12 inches (Correct answer)
- 18 inches
- 24 inches
Correct answer: 12 inches
NEC 680.22(B)(1) requires that luminaires installed in the walls of permanently installed pools be at least 18 inches below the normal water level.
Question 5: NEC Article 525 addresses carnivals, circuses, and fairs. What type of wiring method is prohibited for use as a flexible connection between equipment and supply in these temporary installations?
- Type SO cable
- Type SOOW cable
- Extension cords used as permanent wiring (Correct answer)
- Type G cable
Correct answer: Extension cords used as permanent wiring
Extension cords must not be used as permanent or long-term wiring at carnivals, circuses, and fairs; listed flexible cords and cables suitable for hard or extra-hard usage are required.
Question 6: In a hospital operating room (Class I, Group C and D), what type of electrical system is required to prevent ignition hazards from anesthetic agents?
- Isolated power system with line isolation monitor (Correct answer)
- GFCI-protected circuits only
- Double-insulated equipment on standard circuits
- Dedicated grounded circuits with isolated neutrals
Correct answer: Isolated power system with line isolation monitor
NEC 517.160 requires isolated power systems with line isolation monitors in anesthetizing locations to limit fault current and reduce ignition risk.
Question 7: What NEC article covers electrical installations in marinas and boatyards?
- Article 553
- Article 555 (Correct answer)
- Article 560
- Article 547
Correct answer: Article 555
NEC Article 555 covers electrical installations in marinas, boatyards, and commercial and noncommercial docking facilities.
NEC Special Occupancies & Equipment 3
NEC Article 503 covers Class III locations.
What makes a location Class III?