Lighting Systems and Controls Flashcards
6 cards from real CEM practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Lighting Systems and Controls flashcards as text
What is lumen depreciation?
Answer: The gradual decrease in light output as a lamp ages
Lumen depreciation refers to the reduction in light output that occurs over a lamp's service life due to phosphor degradation and other aging factors.
Which ballast type provides the greatest energy savings for fluorescent lamps?
Answer: Electronic high-frequency ballast
Electronic high-frequency ballasts operate lamps at 20,000+ Hz, eliminating flicker losses and running more efficiently than magnetic ballasts.
The Lighting Power Density (LPD) metric is expressed in:
Answer: Watts per square foot
LPD is expressed as watts per square foot (or W/m²) and is used in energy codes to limit installed lighting power in buildings.
Task-ambient lighting design saves energy compared to uniform lighting by:
Answer: Providing higher illuminance only at work surfaces and lower levels elsewhere
Task-ambient systems deliver high light levels where needed for visual tasks while maintaining lower ambient levels, reducing total installed wattage.
In a lighting retrofit, the simple payback period is calculated as:
Answer: Installed cost divided by annual savings
Simple payback is the initial investment divided by annual energy and maintenance savings, expressing how many years it takes to recover the cost.
High-pressure sodium (HPS) lamps are commonly used in street lighting because they offer:
Answer: High efficacy and long lamp life
HPS lamps deliver 80-150 lm/W efficacy and lifespans of 24,000+ hours, making them cost-effective for outdoor and industrial applications despite poor CRI.