CEA Lighting & HVAC Energy Analysis 4

Question 1

What is the 'cube law' as applied to variable speed HVAC fans and pumps?

Accepted Answer

Energy use varies with the cube of speed

Answer

The affinity law states that fan/pump power varies as the cube of speed, so reducing speed to 80% reduces power to approximately 51% (0.8³ = 0.512).

Question 2

Which lighting metric represents the ratio of lumens emitted by a luminaire to lumens produced by the bare lamp(s) inside?

Accepted Answer

Light Output Ratio (LOR)

Answer

Light Output Ratio (LOR) compares the lumens exiting the fixture to those produced by its lamps, accounting for optical losses within the housing.

Question 3

A retail store has 200 track lights at 75W each. The utility charges a demand charge of $12/kW-month for the peak 15-minute interval. What is the annual demand charge from these lights alone?

Accepted Answer

$2,160

Answer

Peak demand = 200 × 75W = 15,000W = 15 kW; annual demand charge = 15 kW × $12/kW-month × 12 months = $2,160.

Question 4

In HVAC energy analysis, what does 'latent load' refer to?

Accepted Answer

Energy required to change moisture content (humidity) of air

Answer

Latent load is the energy required to add or remove moisture from air without changing its temperature, critical in humid climates.

Question 5

A demand-controlled ventilation (DCV) system reduces outdoor air flow based on which sensor input?

Accepted Answer

CO₂ concentration

Answer

DCV uses CO₂ sensors as a proxy for occupancy; higher CO₂ levels trigger increased outdoor air supply, reducing ventilation energy when spaces are less occupied.

(CEA) Certified Energy Analyst Practice Test

(CEA) Certified Energy Analyst Practice Test

CEA Lighting & HVAC Energy Analysis 4