Certified Energy Auditor HVAC Systems and Controls Questions and Answers

Question 1

An energy auditor is reviewing the Building Automation System (BAS) trend data for a multi-zone Variable Air Volume (VAV) system.
The auditor notes that the supply fan maintains a constant duct static pressure of 2.5 inches w.c. at all times, regardless of the building load.
What is the most effective energy conservation measure to recommend?

Accepted Answer

Implement a duct static pressure reset strategy.

Answer

Increase the chilled water supply temperature setpoint.

Answer

Calibrate all the VAV box damper actuators.

Answer

Replace the existing supply fan with a larger one.

Question 2

What is the primary function of an air-side economizer in an HVAC system?

Accepted Answer

To provide "free cooling" by using cool outside air instead of mechanical refrigeration.

Answer

To pre-heat ventilation air using exhaust air.

Answer

To increase the humidity of the supply air in dry conditions.

Answer

To mix return air with exhaust air before venting to the outside.

Question 3

An energy audit recommends installing a variable frequency drive (VFD) on a constant volume supply fan motor and reducing the fan speed by 20%. According to the fan affinity laws, what is the approximate theoretical reduction in fan power consumption?

Accepted Answer

49%

Answer

36%

Answer

20%

Answer

64%

Question 4

When evaluating the overall energy efficiency of a central water-cooled chiller plant, which of the following metrics is the most comprehensive performance indicator?

Accepted Answer

Total plant efficiency in kW/ton.

Answer

Cooling tower approach temperature.

Answer

Chilled water delta-T (difference between supply and return temperature).

Answer

Chiller coefficient of performance (COP) at full load.

Question 5

During an HVAC system assessment, an auditor measures the chilled water supply temperature at 44°F and the return temperature at 50°F, resulting in a 6°F delta-T. The system was designed for a 12°F delta-T. Which of the following is a likely cause of this "low delta-T syndrome," and what is its primary energy impact?

Accepted Answer

Cause: Oversized chilled water pumps or control valves failing open; Impact: Decreased plant efficiency due to higher pumping energy and inefficient chiller loading.

Answer

Cause: A faulty cooling tower fan; Impact: Increased chiller head pressure.

Answer

Cause: Clogged air filters on the air handling unit; Impact: Reduced airflow, but improved chiller efficiency.

Answer

Cause: The outdoor air economizer is stuck open; Impact: Increased load on the cooling coil, but improved delta-T.

Question 6

Which control strategy adjusts the amount of outdoor ventilation air delivered to a space based on the real-time number of occupants, often by using CO2 sensors?

Accepted Answer

Demand-Controlled Ventilation (DCV)

Answer

Supply Air Temperature Reset

Answer

Optimal Start/Stop

Answer

Enthalpy Economizer Control