Certified Energy Auditor Certification HVAC Systems and Controls 5

Question 1

Which metric best quantifies the overall efficiency of a chilled water plant including pumps, tower fans, and auxiliary equipment?

Accepted Answer

kW/ton of the entire plant

Answer

Plant-level kW/ton accounts for all energy consumers in the chilled water plant, providing a more accurate picture of total system efficiency than chiller-only metrics.

Question 2

What is the purpose of a hot gas bypass in a refrigeration system?

Accepted Answer

Maintain minimum compressor load during light cooling loads

Answer

Hot gas bypass artificially loads the compressor by diverting discharge gas back to the suction side, preventing compressor shutdown during very light loads — though it wastes energy compared to variable capacity compressors.

Question 3

An energy auditor finds that a building's AHU static pressure setpoint is fixed at 1.5 in. w.g. A better control strategy would be:

Accepted Answer

Reset static pressure down until one VAV box is fully open (trim-and-respond)

Answer

Trim-and-respond static pressure reset lowers the setpoint until the most-open VAV box is nearly fully open, minimizing fan energy while still meeting zone loads.

Question 4

What is the significance of a high wet-bulb temperature when evaluating cooling tower performance?

Accepted Answer

It limits how cold the condenser water can get, reducing chiller efficiency

Answer

Cooling towers can only cool condenser water to approximately the outdoor wet-bulb temperature; high wet-bulb limits cooling tower performance and raises condensing pressure in the chiller.

Question 5

When auditing HVAC controls, finding a 'deadband' of only 1°F between heating and cooling setpoints is a problem because:

Accepted Answer

It causes frequent short-cycling and simultaneous operation

Answer

A narrow deadband causes heating and cooling to compete — a small temperature swing triggers one system then the other, wasting energy and causing equipment wear.

Certified Energy Auditor Certification Practice Test

Certified Energy Auditor Certification Practice Test

Certified Energy Auditor Certification HVAC Systems and Controls 5