CLD Luminaire Selection 3 — Questions and Answers
Question 1: A luminaire specification calls for an 'L70' rating of 50,000 hours. What does L70 describe?
- The luminaire loses 70% of its lumens at 50,000 hours
- The luminaire retains 70% of its initial lumens at 50,000 hours (Correct answer)
- The luminaire operates at 70% efficiency for 50,000 hours
- 70% of luminaires tested survived 50,000 hours
Correct answer: The luminaire retains 70% of its initial lumens at 50,000 hours
L70 is the lumen maintenance rating indicating the point at which the LED light source retains 70% of its initial lumen output.
Question 2: For a corridor emergency egress path, which IES luminaire classification best describes a luminaire directing light primarily downward at low angles along a pathway?
- Type II (Correct answer)
- Type III
- Type IV
- Type V
Correct answer: Type II
Type II distribution provides a lateral spread suited for corridors and walkways, directing light ahead along a path from a side-mounted position.
Question 3: A designer selects a luminaire with a Unified Glare Rating (UGR) of 19 for an open office. What does this value indicate?
- The luminaire produces extremely high glare
- The luminaire meets the typical UGR <19 office glare limit (Correct answer)
- The luminaire is below the residential glare threshold
- The luminaire exceeds acceptable educational facility limits
Correct answer: The luminaire meets the typical UGR <19 office glare limit
UGR <19 is the standard threshold for office spaces per EN 12464-1, and a UGR value of exactly 19 sits at the acceptable boundary for typical office tasks.
Question 4: Which luminaire mounting configuration would a CLD specify to minimize veiling reflections on computer screens in an open office?
- Direct downlighting with high output recessed troffers
- Indirect or direct/indirect pendants directing light toward the ceiling (Correct answer)
- Surface-mounted fluorescent strips perpendicular to desks
- Track lighting aimed directly at workstations
Correct answer: Indirect or direct/indirect pendants directing light toward the ceiling
Indirect and direct/indirect pendants bounce light off the ceiling, creating a diffuse luminous environment that minimizes specular reflections on monitor screens.
Question 5: A theatrical performance space requires luminaires capable of tight beam control, color mixing, and remote dimming. Which category best fits this application?
- Architectural linear LED cove
- Entertainment/theatrical ellipsoidal luminaires (Correct answer)
- High-output industrial HID
- Architectural recessed adjustable
Correct answer: Entertainment/theatrical ellipsoidal luminaires
Ellipsoidal luminaires (also called Leko or Source Four fixtures) provide precise beam shaping, gobo projection, and are designed for theatrical color and dimming control.
Question 6: For a healthcare patient room, which color temperature range is recommended to support circadian rhythm and patient well-being during daytime hours?
- 2700K–3000K throughout the day
- 3500K–4000K tunable to 2700K for evening (Correct answer)
- 5000K–6500K maintained all day
- 1800K–2200K amber throughout
Correct answer: 3500K–4000K tunable to 2700K for evening
Tunable white systems providing cooler 3500K–4000K during the day support alertness and circadian rhythms, while dimming to 2700K in the evening promotes sleep.
Question 7: A specification requires luminaires with a minimum efficacy of 100 lumens per watt. Which technology is most likely to achieve this threshold?
- T12 fluorescent with magnetic ballast
- LED with high-efficiency driver (Correct answer)
- Quartz halogen incandescent
- High-pressure sodium HID
Correct answer: LED with high-efficiency driver
Modern LED luminaires routinely achieve 100–200+ lm/W efficacy, far exceeding fluorescent, halogen, and most HID technologies at the luminaire level.
CLD Luminaire Selection 3
A luminaire specification calls for an 'L70' rating of 50,000 hours.
What does L70 describe?