CEA Building Systems & Energy Efficiency 5

Question 1

What is the primary purpose of retro-commissioning (RCx) an existing building?

Accepted Answer

Identifying and correcting operational deficiencies to restore or improve original design performance

Answer

Retro-commissioning systematically investigates existing building systems to find operational and maintenance problems — such as stuck dampers, wrong setpoints, or failed sensors — and corrects them, typically yielding 5–15% energy savings.

Question 2

A simple payback period of 3.2 years means:

Accepted Answer

The initial capital cost is recovered through energy savings in 3.2 years

Answer

Simple payback = initial cost ÷ annual savings; a 3.2-year payback means savings accumulate to equal the upfront investment in 3.2 years, after which the savings are net positive.

Question 3

Which of the following best describes 'whole-building energy use intensity' (EUI)?

Accepted Answer

Annual energy use per square foot of conditioned floor area (kBtu/ft²/yr)

Answer

EUI normalizes total annual energy consumption by conditioned floor area, enabling meaningful comparisons across buildings of different sizes and uses.

Question 4

In a building automation system (BAS), an 'optimal start' algorithm saves energy by:

Accepted Answer

Calculating the latest possible start time to reach setpoint by occupancy, minimizing pre-conditioning hours

Answer

Optimal start learns how long the building takes to reach setpoint under different conditions and delays system startup as long as possible, reducing hours of unoccupied HVAC operation.

Question 5

A facility installs a variable frequency drive (VFD) on a 50 hp cooling tower fan currently running at full speed 8,760 hours/year. If the fan can operate at 80% speed for 70% of hours, what is the approximate energy reduction for those hours?

Accepted Answer

51%

Answer

At 80% speed, power consumption ≈ (0.80)³ = 51.2% of full-load power, meaning approximately 49% savings; the question asks for approximate reduction, which is ~51% reduction in those hours.

(CEA) Certified Energy Analyst Practice Test

(CEA) Certified Energy Analyst Practice Test

CEA Building Systems & Energy Efficiency 5