Lighting Systems and Controls Flashcards

A lighting energy audit should measure which of the following?

Answer: Lamp wattage, fixture count, operating hours, and ballast losses

A complete lighting audit quantifies installed wattage including ballast losses, fixture inventory, and annual operating hours to calculate baseline energy use.

What is the primary benefit of installing occupancy sensors in private offices?

Answer: Energy savings of 20-60% by eliminating lighting in unoccupied spaces

Studies show occupancy sensors in private offices achieve 20-60% lighting energy savings because offices are vacant for significant portions of the workday.

Which metric best represents the overall efficiency of a luminaire including lamp and ballast?

Answer: Luminaire efficacy (system lumens per watt)

Luminaire efficacy (system lm/W) accounts for lamp output, ballast losses, and fixture optical efficiency, providing a complete measure of system performance.

Delamping (removing excess lamps) is a quick energy-saving measure that is most effective when:

Answer: Illuminance levels significantly exceed IES recommended values

When measured illuminance greatly exceeds recommended footcandle levels, removing lamps reduces energy without impairing visual comfort or task performance.

The Illuminating Engineering Society (IES) publishes recommended illuminance levels primarily to:

Answer: Define minimum light levels for safe and productive visual tasks

IES recommended illuminance levels represent minimum light needed for specific visual tasks to ensure safety, comfort, and productivity without over-lighting.

Dimming controls on fluorescent and LED systems typically save energy in proportion to:

Answer: The reduction in light output (approximately linear)

For electronic ballasts and LED drivers, power consumption decreases approximately linearly with light output reduction, so 50% dimming yields roughly 50% energy savings.