Certified Energy Auditor Certification HVAC Systems and Performance 3

Question 1

When performing a duct leakage test, what does CFM25 indicate?

Accepted Answer

Cubic feet per minute of airflow at 25 Pa pressure differential

Answer

CFM25 is the measured duct leakage airflow in cubic feet per minute at a reference pressure of 25 Pascals.

Question 2

What is the function of an economizer cycle in a commercial HVAC system?

Accepted Answer

Use outdoor air for free cooling when conditions allow

Answer

An economizer opens outdoor air dampers to use cool outdoor air for free cooling, reducing or eliminating mechanical refrigeration.

Question 3

A building's HVAC system uses a pneumatic control system. What is a major energy-efficiency concern with this type of system?

Accepted Answer

Hunting and poor setpoint accuracy increasing energy use

Answer

Pneumatic controls are prone to hunting and calibration drift, leading to wider temperature swings and higher energy consumption compared to direct digital control.

Question 4

In a hydronic system, what does 'delta-T' refer to?

Accepted Answer

Temperature difference between supply and return water

Answer

Delta-T (ΔT) in a hydronic system is the temperature difference between the supply water and the return water, indicating heat transfer effectiveness.

Question 5

Which fan law states that fan power varies with the cube of the fan speed?

Accepted Answer

Third fan law

Answer

The third fan law (power affinity law) states that power varies as the cube of the speed ratio, which is why VFDs yield dramatic energy savings.

Certified Energy Auditor Certification Practice Test

Certified Energy Auditor Certification Practice Test

Certified Energy Auditor Certification HVAC Systems and Performance 3