Certified Energy Auditor Lighting and Electrical Systems Questions and Answers ā Questions and Answers
Question 1: An energy auditor is evaluating four different LED lamp options for a retrofit project. Which of the following lamps is the most energy-efficacious?
- Lamp A: 1600 lumens, 15 watts
- Lamp B: 1200 lumens, 10 watts
- Lamp C: 2000 lumens, 20 watts
- Lamp D: 800 lumens, 5 watts (Correct answer)
Correct answer: Lamp D: 800 lumens, 5 watts
Luminous efficacy is the ratio of light output (lumens) to power input (watts). A higher lumens-per-watt (LPW) value indicates greater efficacy. Lamp D has an efficacy of 800 lm / 5 W = 160 LPW, which is the highest among the options (Lamp A: 106.7 LPW, Lamp B: 120.0 LPW, Lamp C: 100.0 LPW).
Question 2: During a facility audit, the utility bills for a manufacturing plant show a consistent power factor penalty charge each month. The plant's load consists primarily of large induction motors. Which of the following is the most direct and cost-effective solution to mitigate these penalty charges?
- Replacing all motors with premium efficiency models
- Upgrading the facility's main transformer
- Installing appropriately sized capacitor banks (Correct answer)
- Increasing the operating voltage of the facility
Correct answer: Installing appropriately sized capacitor banks
Inductive loads, like motors, cause a lagging power factor by drawing reactive power. Capacitor banks provide leading reactive power to the system, which counteracts the lagging reactive power from the motors. This improves the power factor, reducing the total current drawn from the utility and eliminating penalty charges. While upgrading motors can help, it's a much larger capital expense and may not fully resolve the issue.
Question 3: An energy auditor is assessing an open-plan office with large perimeter windows that provide significant natural light throughout the day. To maximize energy savings, which lighting control strategy would be most effective for the rows of luminaires closest to the windows?
- Time-of-day scheduling
- Ultrasonic occupancy sensors
- Daylight harvesting with continuous dimming (Correct answer)
- Manual wall-box dimmers for each zone
Correct answer: Daylight harvesting with continuous dimming
Daylight harvesting systems use photosensors to measure the amount of ambient light and automatically dim the electric lights when sufficient natural light is available. This strategy is ideal for spaces with significant daylight contribution, such as areas near windows, and provides continuous adjustment for maximum savings and occupant comfort.
Question 4: Which of the following is the primary source of harmonic currents in a modern commercial office building's electrical system?
- Incandescent lighting
- Synchronous motors for large fans
- Non-linear loads like computer power supplies and electronic ballasts (Correct answer)
- Step-down distribution transformers
Correct answer: Non-linear loads like computer power supplies and electronic ballasts
Non-linear loads, which do not draw current in a sinusoidal manner, are the main cause of harmonic distortion. Modern offices are filled with these loads, including switch-mode power supplies for computers and printers, electronic lighting ballasts, and variable frequency drives (VFDs) in HVAC systems.
Question 5: An energy auditor is analyzing the performance of a large distribution transformer. Which type of transformer loss remains relatively constant regardless of the load level, as long as the transformer is energized?
- Load (copper) losses
- No-load (core) losses (Correct answer)
- Stray losses
- Resistive (IĀ²R) losses
Correct answer: No-load (core) losses
No-load losses, also known as core or iron losses, are caused by the alternating magnetic field in the transformer's core. These losses (hysteresis and eddy current losses) occur whenever the transformer is energized, even with no load connected, and are dependent on the voltage, not the load current.
Question 6: When conducting a lighting audit, an auditor uses a light meter to take readings on desktops and work surfaces throughout a space. What quantity is the auditor measuring, and what are its common units?
- Luminous Flux, measured in Lumens
- Luminous Efficacy, measured in Lumens per Watt
- Illuminance, measured in Foot-candles or Lux (Correct answer)
- Color Rendering Index (CRI), measured on a scale of 0-100
Correct answer: Illuminance, measured in Foot-candles or Lux
The auditor is measuring illuminance, which is the amount of light falling on a specific surface area. The common imperial unit for this measurement is the foot-candle (one lumen per square foot), while the SI unit is lux (one lumen per square meter). Luminous flux (lumens) refers to the total light emitted by a source, not the light arriving at a surface.
Certified Energy Auditor Lighting and Electrical Systems Questions and Answers
An energy auditor is evaluating four different LED lamp options for a retrofit project.
Which of the following lamps is the most energy-efficacious?