CEA Lighting & HVAC Energy Analysis 2 — Questions and Answers
Question 1: A facility manager wants to reduce lighting energy use by installing occupancy sensors in private offices. What percentage energy savings is typically achievable in private office spaces?
- 10–15%
- 20–30%
- 40–50% (Correct answer)
- 60–70%
Correct answer: 40–50%
Occupancy sensors in private offices typically reduce lighting energy by 40–50% because offices are frequently unoccupied during the workday.
Question 2: Which HVAC system type uses a single refrigerant circuit to serve multiple indoor units, allowing individual zone control?
- Chilled water system
- Variable refrigerant flow (VRF) system (Correct answer)
- Constant air volume (CAV) system
- Single-zone packaged unit
Correct answer: Variable refrigerant flow (VRF) system
VRF systems use one refrigerant circuit connected to multiple indoor fan-coil units, enabling independent zone temperature control.
Question 3: What does a Lighting Power Density (LPD) value measure?
- Total lumens per fixture
- Watts of lighting power per square foot of floor area (Correct answer)
- Candela output per luminaire
- Foot-candles at the task plane
Correct answer: Watts of lighting power per square foot of floor area
LPD is expressed in watts per square foot (W/ft²) and is the primary metric used by ASHRAE 90.1 to regulate interior lighting energy use.
Question 4: In HVAC energy analysis, what is the significance of the 'bin method'?
- It classifies equipment by EER rating bins
- It groups outdoor temperature hours into bins to estimate annual energy consumption (Correct answer)
- It organizes duct leakage test results
- It categorizes refrigerants by GWP tiers
Correct answer: It groups outdoor temperature hours into bins to estimate annual energy consumption
The bin method divides annual outdoor temperature data into temperature bins, then calculates energy use at each bin to estimate total annual HVAC energy consumption.
Question 5: A T8 fluorescent lamp operates at 32 watts. An equivalent LED tube replacement operates at 18 watts. What is the percentage wattage reduction?
- 33%
- 44% (Correct answer)
- 56%
- 78%
Correct answer: 44%
The reduction is (32−18) ÷ 32 = 14 ÷ 32 ≈ 43.75%, which rounds to approximately 44%.
Question 6: Which metric best describes the overall efficiency of a chiller plant including cooling tower, condenser pump, and chilled water pump energy?
- EER
- COP
- kW/ton (Correct answer)
- SEER
Correct answer: kW/ton
kW/ton (kilowatts per ton of cooling) is the standard metric for evaluating chiller plant efficiency, encompassing all plant auxiliaries.
Question 7: What is 'daylighting' in the context of building energy analysis?
- Scheduling HVAC to operate only during daylight hours
- Using natural light to offset electric lighting energy consumption (Correct answer)
- Painting walls white to improve reflectance
- Installing skylights solely for occupant comfort
Correct answer: Using natural light to offset electric lighting energy consumption
Daylighting uses sunlight entering through windows or skylights to reduce electric lighting loads, often paired with daylight-responsive dimming controls.
CEA Lighting & HVAC Energy Analysis 2
A facility manager wants to reduce lighting energy use by installing occupancy sensors in private offices.
What percentage energy savings is typically achievable in private office spaces?