Certified Energy Auditor Certification Certified Energy Auditor HVAC Systems and Performance 1

Question 1

A heat pump in heating mode is measured to have a coefficient of performance (COP) of 3.2. What does this value mean in practical terms?

Accepted Answer

The system produces 3.2 BTUs of heat for every BTU of electrical energy consumed

Answer

COP is the ratio of useful heat output to electrical energy input. A COP of 3.2 means the heat pump delivers 3.2 units of heat energy for every 1 unit of electrical energy consumed, making it far more efficient than resistance heating (COP = 1.0).

Question 2

An energy auditor inspects a commercial air handling unit with an enthalpy-based economizer. Under which condition should the economizer damper be commanded to 100% open?

Accepted Answer

Outdoor air enthalpy is lower than return air enthalpy and mechanical cooling is active

Answer

An enthalpy-based economizer compares the total heat content (sensible + latent) of outdoor air versus return air. When outdoor enthalpy is lower, bringing in 100% outdoor air provides free cooling and reduces compressor runtime, saving energy.

Question 3

Applying the fan affinity laws, if a variable frequency drive (VFD) reduces a centrifugal fan's motor speed from 1,200 RPM to 900 RPM, the resulting power consumption will be approximately what fraction of the original?

Accepted Answer

42% of original power (varies as the cube of speed ratio)

Answer

The fan affinity laws state that power varies as the cube of the speed ratio. (900/1200)³ = (0.75)³ = 0.422, so power drops to approximately 42% of original — a dramatic saving that makes VFDs one of the highest-ROI energy efficiency measures in HVAC.

Question 4

During an energy audit of a large commercial building, an auditor wants to quantify duct leakage to the outside. Which test method directly measures this?

Accepted Answer

Duct pressurization test using a calibrated fan to pressurize the duct system while supply and return registers are sealed

Answer

A duct pressurization test (using a 'duct blaster') seals all registers and pressurizes the duct to a reference pressure (typically 25 Pa). The airflow required to maintain that pressure equals the duct leakage rate, expressed in CFM25. This directly quantifies distribution losses.

Question 5

A central chiller plant consumes 480 kW of electrical power while producing 1,200 tons of cooling. What is the plant's efficiency expressed in the metric most commonly used by energy auditors for chiller evaluation?

Accepted Answer

0.40 kW/ton and 2.50 tons/kW are both correct representations of the same efficiency

Answer

Chiller efficiency is expressed as kW/ton (lower is better) or its reciprocal tons/kW (higher is better). Here: 480 kW ÷ 1,200 tons = 0.40 kW/ton, and 1,200 tons ÷ 480 kW = 2.50 tons/kW. Both values describe the same operating point and auditors may use either.

Certified Energy Auditor Certification Practice Test

Certified Energy Auditor Certification Practice Test

Certified Energy Auditor Certification Certified Energy Auditor HVAC Systems and Performance 1