Certified Energy Auditor Certification HVAC Systems and Performance 5

Question 1

What is 'thermal stratification' in a large commercial space and why does it matter for energy efficiency?

Accepted Answer

Temperature layering where hot air accumulates near the ceiling, increasing heating energy if not destratified

Answer

Warm air rises and stratifies near the ceiling in tall spaces; heating energy is wasted warming unconditioned upper zones unless destratification fans mix the air.

Question 2

Which control strategy can reduce chiller plant energy use by raising chilled water supply temperature during low-load conditions?

Accepted Answer

Chilled water temperature reset

Answer

Chilled water supply temperature reset raises the setpoint when cooling loads are low, allowing the chiller to operate at a higher suction pressure and lower kW/ton.

Question 3

An auditor finds that a 50-hp supply fan motor runs 8,760 hours/year at full speed. Installing a VFD that reduces average speed to 80% would reduce annual kWh consumption by approximately how much?

Accepted Answer

51%

Answer

By the cube law, power at 80% speed = 0.8³ = 0.512, so energy savings ≈ 1 – 0.512 = 48.8%, approximately 51%.

Question 4

What is 'integrated part-load value' (IPLV) used to characterize?

Accepted Answer

A weighted average chiller efficiency across multiple part-load conditions

Answer

IPLV is a weighted average of chiller COP or kW/ton measured at 100%, 75%, 50%, and 25% load conditions, reflecting real-world part-load operation.

Question 5

A maintenance log shows a split-system air conditioner's condenser coils are heavily fouled with dirt. What is the most direct energy impact?

Accepted Answer

Increased condensing temperature raises compressor power and reduces efficiency

Answer

Fouled condenser coils restrict airflow and heat transfer, raising condensing temperature and pressure, which forces the compressor to work harder and reduces efficiency.

Certified Energy Auditor Certification Practice Test

Certified Energy Auditor Certification Practice Test

Certified Energy Auditor Certification HVAC Systems and Performance 5