Lighting Systems Flashcards

ASHRAE Standard 90.1 addresses lighting in the context of:

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.

Lamp lumen depreciation (LLD) refers to:

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.

Which lighting technology offers the highest luminous efficacy (lumens per watt) among current commercially available sources?

Answer: LED

Modern LED sources can achieve 150–200+ lm/W, surpassing all other commercially available lighting technologies.

A retail store wants to highlight merchandise with tight beam spreads. Which luminaire characteristic best describes beam control?

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.

In lighting controls, a closed-loop daylight harvesting system differs from an open-loop system because it:

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.

The rated life of a fluorescent lamp (e.g., 20,000 hours) is defined as the point at which:

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.

Exit signs and emergency lighting systems in US commercial buildings must comply with which standard?

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.