CET Traveling Cables & Wiring Methods 2 — Questions and Answers
Question 1: Which NEC article specifically governs electrical wiring and equipment for elevators, dumbwaiters, escalators, and moving walks?
- NEC Article 430 — Motors, Motor Circuits, and Controllers
- NEC Article 620 — Elevators, Dumbwaiters, Escalators, Moving Walks, Platform Lifts, and Stairway Lifts (Correct answer)
- NEC Article 480 — Storage Batteries
- NEC Article 517 — Health Care Facilities
Correct answer: NEC Article 620 — Elevators, Dumbwaiters, Escalators, Moving Walks, Platform Lifts, and Stairway Lifts
NEC Article 620 is the dedicated article covering all electrical requirements for vertical and horizontal transportation equipment including elevators, escalators, and moving walks.
Question 2: Per NEC Article 620, which wiring method is approved for use inside elevator hoistways?
- Non-metallic sheathed cable (NM-B) stapled to hoistway concrete
- Open wiring on porcelain insulators at 4-foot intervals
- Rigid metal conduit (RMC), intermediate metal conduit (IMC), or electrical metallic tubing (EMT) (Correct answer)
- Armored cable (AC) stapled at 4-foot maximum intervals
Correct answer: Rigid metal conduit (RMC), intermediate metal conduit (IMC), or electrical metallic tubing (EMT)
NEC Article 620 requires conductors in hoistways to be installed in metal raceways such as RMC, IMC, or EMT to protect wiring from the mechanical hazards present in the hoistway environment.
Question 3: Which of the following wiring methods is NOT permitted in an elevator machine room per NEC Article 620?
- Rigid metal conduit (RMC)
- Electrical metallic tubing (EMT)
- Non-metallic sheathed cable (NM-B, commonly called Romex) (Correct answer)
- Metal wireways and auxiliary gutters
Correct answer: Non-metallic sheathed cable (NM-B, commonly called Romex)
NEC Article 620 prohibits non-metallic sheathed cable in elevator machine rooms; only metallic raceways and other specifically permitted methods are allowed.
Question 4: Per NEC 620.24, the elevator pit lighting circuit must be:
- A 277V circuit shared with the machine room lighting to reduce wiring costs
- A separate lighting circuit with a disconnect means accessible at the pit entrance (Correct answer)
- A battery-backed emergency circuit providing only 90 minutes of illumination
- Supplied from the same branch circuit as the car lighting
Correct answer: A separate lighting circuit with a disconnect means accessible at the pit entrance
The pit must have a dedicated lighting circuit with a disconnect accessible at the pit entrance so technicians can control pit lighting before entry, ensuring they can see safely without depending on others.
Question 5: Per NEC 620.22, elevator car lighting circuits must not exceed which voltage rating?
- 480V to permit use of standard building fluorescent fixtures
- 277V consistent with commercial branch circuit standards
- 120V to protect car occupants from high-voltage hazards (Correct answer)
- 24V for low-voltage safety compliance
Correct answer: 120V to protect car occupants from high-voltage hazards
NEC 620.22 limits elevator car lighting to 120V maximum because the car is an occupied space, and lower voltage reduces shock hazard risk to passengers and technicians.
Question 6: Per NEC 620.51, the main line disconnecting means for elevator equipment must be located:
- Inside the elevator car so occupants can shut off power in emergencies
- At the building main service panel only, centralized for fire department access
- In the machine room or machinery space, accessible only to qualified personnel (Correct answer)
- In the pit to allow technicians to de-energize before pit entry
Correct answer: In the machine room or machinery space, accessible only to qualified personnel
NEC 620.51 requires the main disconnecting means to be in the machine room or machinery space so that only qualified elevator technicians can de-energize the equipment.
Question 7: When sizing elevator feeder conductors supplying multiple elevator motors per NEC 620.13, the ampacity must be based on:
- The sum of all motor nameplate currents with no multiplier applied
- 125% of the largest motor nameplate current plus 100% of all remaining motor nameplate currents (Correct answer)
- 200% of the total connected load to account for simultaneous starting
- Only the highest demand motor, with other motors considered backup only
Correct answer: 125% of the largest motor nameplate current plus 100% of all remaining motor nameplate currents
NEC 620.13 requires feeder conductors to carry 125% of the largest motor's nameplate current (to account for starting current) plus 100% of all other motor currents.
CET Traveling Cables & Wiring Methods 2
Which NEC article specifically governs electrical wiring and equipment for elevators, dumbwaiters, escalators, and moving walks?