CEM Lighting Systems 4 — Questions and Answers
Question 1: ASHRAE Standard 90.1 addresses lighting in the context of:
- Minimum lamp efficacy requirements only
- Energy efficiency of buildings including lighting power density limits (Correct answer)
- OSHA workplace illuminance mandates
- Flicker and power quality for electronic ballasts
Correct answer: Energy efficiency of buildings including lighting power density limits
ASHRAE 90.1 sets energy efficiency requirements for commercial buildings, including maximum LPD limits by space and building type.
Question 2: Lamp lumen depreciation (LLD) refers to:
- The reduction in fixture efficiency due to dirt accumulation
- The gradual decrease in lumen output as a lamp ages (Correct answer)
- The loss of lumens due to poor room surface reflectances
- The reduction in lumens caused by low power factor ballasts
Correct answer: The gradual decrease in lumen output as a lamp ages
LLD is the ratio of lumens at a specific point in lamp life to initial lumens, reflecting gradual output decline.
Question 3: Which lighting technology offers the highest luminous efficacy (lumens per watt) among current commercially available sources?
- T8 fluorescent with electronic ballast
- High-pressure sodium (HPS)
- LED (Correct answer)
- Metal halide ceramic
Correct answer: LED
Modern LED sources can achieve 150–200+ lm/W, surpassing all other commercially available lighting technologies.
Question 4: A retail store wants to highlight merchandise with tight beam spreads. Which luminaire characteristic best describes beam control?
- Color Rendering Index (CRI)
- Beam angle or field angle (Correct answer)
- Correlated Color Temperature (CCT)
- Ballast factor
Correct answer: Beam angle or field angle
Beam angle (where intensity drops to 50% of peak) and field angle (10% of peak) define how tightly or broadly a luminaire concentrates light.
Question 5: In lighting controls, a closed-loop daylight harvesting system differs from an open-loop system because it:
- Uses a fixed dimming schedule based on sunrise/sunset times
- Measures actual workplane illuminance and adjusts electric light to meet a setpoint (Correct answer)
- Only responds to outdoor light levels without measuring interior conditions
- Controls lighting based solely on occupancy sensor data
Correct answer: Measures actual workplane illuminance and adjusts electric light to meet a setpoint
A closed-loop system uses a photosensor measuring workplane illuminance to maintain a target level by adjusting electric light output.
Question 6: The rated life of a fluorescent lamp (e.g., 20,000 hours) is defined as the point at which:
- All lamps in a test batch have burned out
- 50% of lamps in a statistically tested sample have failed (Correct answer)
- Lumen output has dropped to 50% of initial
- The ballast factor has decreased to 0.90
Correct answer: 50% of lamps in a statistically tested sample have failed
Rated lamp life is the median life (B50 life) — the hours at which 50% of a large sample of lamps have failed under standard test conditions.
Question 7: Exit signs and emergency lighting systems in US commercial buildings must comply with which standard?
- ASHRAE 90.1
- NFPA 101 Life Safety Code (Correct answer)
- IESNA RP-1
- IEEE 519
Correct answer: NFPA 101 Life Safety Code
NFPA 101, the Life Safety Code, mandates emergency lighting and exit sign requirements to ensure safe egress during power failures.
CEM Lighting Systems 4
ASHRAE Standard 90.1 addresses lighting in the context of: