CLD Electrical Systems & Lighting Control 2 — Questions and Answers
Question 1: A 0–10V dimming system receives a control signal of 5V. What approximate output level should the driver produce?
- 25% output
- 50% output (Correct answer)
- 75% output
- 100% output
Correct answer: 50% output
In a 0–10V system, 5V corresponds to approximately 50% light output on a linear scale.
Question 2: Which wiring method is required by NEC for circuits serving luminaires in a swimming pool wet niche?
- Type NM cable
- Type SE cable
- Type MC cable or rigid conduit (Correct answer)
- Type AC cable
Correct answer: Type MC cable or rigid conduit
NEC Article 680 requires luminaires in wet niches to be wired with approved conduit or Type MC cable rated for wet locations.
Question 3: What is the primary advantage of using a centralized lighting control system over distributed zone dimmers?
- Lower initial equipment cost
- Simpler installation wiring
- Single-point programming and system-wide scene coordination (Correct answer)
- Reduced heat dissipation
Correct answer: Single-point programming and system-wide scene coordination
Centralized systems allow all zones to be programmed, scheduled, and coordinated from one processor, enabling complex scenes impossible with standalone dimmers.
Question 4: A designer specifies a 277V LED driver. On which distribution system is this voltage commonly found?
- 120/208V three-phase wye
- 120/240V single-phase
- 277/480V three-phase wye (Correct answer)
- 240/415V three-phase delta
Correct answer: 277/480V three-phase wye
277V is the phase-to-neutral voltage of a 277/480V three-phase wye system, common in commercial buildings.
Question 5: DALI (Digital Addressable Lighting Interface) supports up to how many individually addressable devices on a single bus segment?
- 16
- 32
- 64 (Correct answer)
- 128
Correct answer: 64
The DALI standard (IEC 62386) allows up to 64 individual device addresses per bus segment.
Question 6: Which type of occupancy sensor technology is best suited for detecting minor motion in large open-plan offices?
- Passive infrared (PIR) only
- Ultrasonic only
- Dual-technology (PIR + ultrasonic) (Correct answer)
- Microwave only
Correct answer: Dual-technology (PIR + ultrasonic)
Dual-technology sensors combine PIR thermal detection with ultrasonic motion detection, reducing false-offs in large spaces with subtle movement.
Question 7: When calculating voltage drop for a long lighting circuit run, which formula correctly expresses the drop for a single-phase circuit?
- VD = I × R
- VD = 2 × I × R × L (Correct answer)
- VD = I × R × L / 1000
- VD = √3 × I × R × L
Correct answer: VD = 2 × I × R × L
For single-phase circuits, voltage drop equals 2 × current × resistance per unit length × length, accounting for both the hot and neutral conductors.
CLD Electrical Systems & Lighting Control 2
A 0–10V dimming system receives a control signal of 5V.
What approximate output level should the driver produce?