Lighting Systems Flashcards

A warehouse currently uses 400W metal halide fixtures. Replacing them with 150W LED high-bays maintains light levels. What is the percentage energy reduction?

Answer: 62.5%

Energy reduction = (400-150)/400 × 100 = 62.5%.

Which lighting control strategy automatically reduces output based on available daylight near perimeter windows?

Answer: Daylight harvesting

Daylight harvesting uses photosensors to dim electric lights as natural light increases.

The Color Rendering Index (CRI) measures which lamp characteristic?

Answer: Accuracy of color appearance compared to a reference source

CRI rates how accurately a light source renders object colors relative to a reference illuminant on a 0–100 scale.

An office space requires 50 foot-candles at the work plane. The room has an area of 2,000 sq ft and luminaires with 3,200 lumens each. Using a CU of 0.65 and LLF of 0.80, how many luminaires are needed?

Answer: 60

N = (50 × 2000) / (3200 × 0.65 × 0.80) = 100,000 / 1,664 ≈ 60 luminaires.

Which term describes the fraction of lamp lumens that actually reach the work plane, accounting for fixture efficiency and room geometry?

Answer: Coefficient of Utilization (CU)

The Coefficient of Utilization (CU) represents the ratio of lumens reaching the work plane to total lamp lumens.

LED drivers with 0-10V dimming protocol dim a fixture to what minimum output level before the light turns off?

Answer: 10%

In 0-10V dimming, 1V corresponds to the minimum dim level (typically ~10%) and 10V is full output; below 1V the fixture switches off.

A facility manager wants to reduce lighting power density (LPD) to comply with ASHRAE 90.1. Which metric directly expresses LPD?

Answer: Watts per square foot

Lighting Power Density (LPD) is expressed in watts per square foot (W/ft²) and is the standard metric in ASHRAE 90.1.