Certified Energy Auditor Certification Certified Energy Auditor HVAC Systems and Controls Questions and Answers 2 — Questions and Answers
Question 1: What is the primary advantage of a variable air volume (VAV) system compared to a constant air volume (CAV) system in commercial buildings?
- Reduced fan energy consumption at partial loads (Correct answer)
- Lower initial installation cost
- Simpler maintenance requirements
- Better humidity control at all loads
Correct answer: Reduced fan energy consumption at partial loads
VAV systems reduce fan energy by modulating airflow to match actual zone demands, significantly cutting energy use at partial loads.
Question 2: During an energy audit, which measurement is most critical for evaluating the efficiency of a chiller plant?
- kW per ton of cooling (Correct answer)
- Supply air temperature
- Condenser water flow rate
- Refrigerant charge level
Correct answer: kW per ton of cooling
The kW/ton metric directly quantifies how much electrical energy the chiller consumes per unit of cooling output, making it the standard efficiency benchmark.
Question 3: What does an economizer cycle on a rooftop HVAC unit accomplish?
- Uses outdoor air for free cooling when conditions permit (Correct answer)
- Recovers heat from exhaust air streams
- Reduces refrigerant charge requirements
- Increases compressor efficiency at low ambient temperatures
Correct answer: Uses outdoor air for free cooling when conditions permit
An economizer cycle introduces outdoor air to provide free cooling when the outside temperature and humidity are favorable, reducing mechanical cooling loads.
Question 4: Which control strategy is most effective for reducing energy consumption in a multi-zone HVAC system experiencing simultaneous heating and cooling?
- Resetting supply air temperature based on zone demands (Correct answer)
- Lowering the thermostat setpoint uniformly
- Increasing minimum airflow setpoints
- Adding supplemental electric reheat coils
Correct answer: Resetting supply air temperature based on zone demands
Supply air temperature reset reduces simultaneous heating and cooling by raising the supply air temperature when cooling demand is low, minimizing reheat energy.
Question 5: What is the recommended approach when an energy auditor discovers that building static pressure setpoints are significantly higher than necessary?
- Lower the static pressure setpoint and verify zone comfort is maintained (Correct answer)
- Replace the supply fan with a smaller model
- Install additional VAV boxes to reduce duct pressure
- Increase duct insulation to compensate for pressure losses
Correct answer: Lower the static pressure setpoint and verify zone comfort is maintained
Reducing an unnecessarily high static pressure setpoint directly lowers fan energy consumption while maintaining adequate airflow if comfort conditions are verified.
Question 6: In a direct digital control (DDC) system, what is the function of the proportional-integral (PI) control loop for a cooling coil valve?
- Modulates the valve position to maintain discharge air temperature at setpoint (Correct answer)
- Opens the valve fully whenever cooling is needed
- Cycles the valve between fully open and fully closed at fixed intervals
- Maintains a constant water flow rate regardless of load
Correct answer: Modulates the valve position to maintain discharge air temperature at setpoint
A PI control loop continuously adjusts the cooling coil valve position to minimize the error between actual discharge air temperature and the desired setpoint.
Certified Energy Auditor Certification Certified Energy Auditor HVAC Systems and Controls Questions and Answers 2
What is the primary advantage of a variable air volume (VAV) system compared to a constant air volume (CAV) system in commercial buildings?