Certified Energy Auditor Certification Lighting and Electrical Systems 3 — Questions and Answers
Question 1: What is the primary advantage of a daylight harvesting control system in perimeter office zones?
- It eliminates the need for emergency lighting
- It dims or switches off electric lights when daylight provides sufficient illuminance (Correct answer)
- It adjusts lamp color temperature based on time of day
- It reduces transformer losses during daytime hours
Correct answer: It dims or switches off electric lights when daylight provides sufficient illuminance
Daylight harvesting uses photosensors to continuously dim or switch electric lighting when sufficient natural light is available, reducing electrical energy use.
Question 2: A 480V/277V three-phase system distributes power to lighting panels. What is the advantage of 277V branch circuits for commercial lighting?
- Lower current for the same wattage reduces conductor and breaker costs (Correct answer)
- 277V fixtures have higher CRI ratings
- 277V eliminates the need for ballasts
- Lower voltage reduces transformer losses
Correct answer: Lower current for the same wattage reduces conductor and breaker costs
At 277V, the current for the same wattage load is approximately half that at 120V, allowing smaller conductors and reducing distribution losses.
Question 3: Which LED driver topology provides the best efficiency over a wide dimming range?
- Linear regulator driver
- Constant-voltage driver with resistor
- 0-10V analog dimming driver
- Pulse-width modulation (PWM) driver (Correct answer)
Correct answer: Pulse-width modulation (PWM) driver
PWM drivers switch current on and off rapidly, maintaining full LED drive current per pulse so efficacy stays high even at low dim levels.
Question 4: An auditor calculates that replacing 200 W metal halide high-bay fixtures with 90 W LED high-bays will save 22 kW of demand. At $12/kW/month demand charge, what is the annual demand savings?
- $1,584
- $2,376
- $3,168 (Correct answer)
- $3,960
Correct answer: $3,168
22 kW × $12/kW/month × 12 months = $3,168 per year in demand charge savings.
Question 5: What does 'stroboscopic effect' mean in the context of lighting for rotating machinery?
- The flickering of lamps at end of life
- The apparent slowing or stopping of rotating parts when light flickers at multiples of rotational speed (Correct answer)
- Glare from high-reflectance surfaces near machinery
- The color shift experienced when switching lamp types
Correct answer: The apparent slowing or stopping of rotating parts when light flickers at multiples of rotational speed
When light flickers at a frequency equal to or a multiple of the rotation speed, moving parts can appear stationary, creating a safety hazard.
Question 6: Under ASHRAE 90.1, which control is mandatory for all interior lighting in spaces larger than 5,000 ft²?
- Occupancy sensors
- Automatic time-switch controls (Correct answer)
- Daylight sensors
- Manual dimming controls
Correct answer: Automatic time-switch controls
ASHRAE 90.1 requires automatic time-switch or scheduling controls for interior lighting in spaces over 5,000 ft² to ensure lights are turned off after hours.
Question 7: Which transformer type produces the lowest no-load (core) losses for distribution to lighting panels?
- Standard efficiency dry-type transformer
- Liquid-filled transformer
- Amorphous core transformer (Correct answer)
- K-rated transformer
Correct answer: Amorphous core transformer
Amorphous core transformers use an amorphous metal alloy that significantly reduces hysteresis losses, cutting no-load losses by up to 70% versus standard silicon-steel cores.
Certified Energy Auditor Certification Lighting and Electrical Systems 3
What is the primary advantage of a daylight harvesting control system in perimeter office zones?