ASHRAE Mechanical Systems Design
Competency Assessment Exam Practice
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. A variable air volume (VAV) system primarily controls space
temperature by:
A. Maintaining constant supply air temperature and varying airflow
rate
B. Maintaining constant airflow rate and varying supply air
temperature
C. Varying both airflow and humidity simultaneously
D. Maintaining constant return air temperature
Answer: A
Rationale: VAV systems regulate zone temperature by adjusting the
quantity of supply air while typically maintaining a relatively
constant supply air temperature.
,2. In psychrometric processes, sensible cooling of air is represented by:
A. Horizontal movement to the right
B. Vertical upward movement
C. Horizontal movement to the left
D. Diagonal upward-right movement
Answer: C
Rationale: Sensible cooling reduces dry-bulb temperature without
changing moisture content, moving left on the psychrometric chart.
3. The main purpose of a chilled water bypass line in a primary-
secondary system is to:
A. Increase pump efficiency
B. Maintain minimum flow through chillers
C. Reduce condenser pressure
D. Increase cooling tower efficiency
Answer: B
Rationale: The bypass ensures minimum flow through chillers to
prevent damage and maintain stable operation.
4. Which HVAC system is most suitable for high-rise buildings with
varying loads?
A. Constant air volume system
B. Packaged terminal air conditioner system
C. Variable air volume system
D. Window air conditioning system
, Answer: C
Rationale: VAV systems efficiently handle varying loads across
multiple zones, making them ideal for high-rise buildings.
5. Heat recovery ventilators primarily function to:
A. Increase refrigeration capacity
B. Transfer heat between exhaust and incoming air streams
C. Remove latent heat only
D. Increase air infiltration rates
Answer: B
Rationale: Heat recovery ventilators transfer sensible and sometimes
latent heat between air streams to improve efficiency.
6. In HVAC design, latent heat refers to:
A. Heat causing temperature change only
B. Heat associated with phase change of moisture
C. Heat from electrical equipment
D. Heat lost through conduction only
Answer: B
Rationale: Latent heat involves energy absorbed or released during
moisture phase changes without temperature change.
7. The function of an economizer cycle is to:
A. Reduce compressor size
B. Use outdoor air for free cooling when conditions permit
C. Increase refrigeration load
, D. Reduce duct static pressure
Answer: B
Rationale: Economizers use favorable outdoor conditions to reduce
mechanical cooling demand.
8. Which component controls refrigerant flow into the evaporator?
A. Compressor
B. Condenser
C. Expansion valve
D. Cooling tower
Answer: C
Rationale: The expansion valve regulates refrigerant flow and
pressure entering the evaporator.
9. Air changes per hour (ACH) is defined as:
A. Air volume per unit floor area
B. Number of times room air is replaced in one hour
C. Supply air temperature changes per hour
D. Fan speed variations per hour
Answer: B
Rationale: ACH measures how frequently the total room air volume is
replaced each hour.
10. A cooling tower primarily removes heat through:
A. Conduction only
B. Evaporation and convection
Competency Assessment Exam Practice
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. A variable air volume (VAV) system primarily controls space
temperature by:
A. Maintaining constant supply air temperature and varying airflow
rate
B. Maintaining constant airflow rate and varying supply air
temperature
C. Varying both airflow and humidity simultaneously
D. Maintaining constant return air temperature
Answer: A
Rationale: VAV systems regulate zone temperature by adjusting the
quantity of supply air while typically maintaining a relatively
constant supply air temperature.
,2. In psychrometric processes, sensible cooling of air is represented by:
A. Horizontal movement to the right
B. Vertical upward movement
C. Horizontal movement to the left
D. Diagonal upward-right movement
Answer: C
Rationale: Sensible cooling reduces dry-bulb temperature without
changing moisture content, moving left on the psychrometric chart.
3. The main purpose of a chilled water bypass line in a primary-
secondary system is to:
A. Increase pump efficiency
B. Maintain minimum flow through chillers
C. Reduce condenser pressure
D. Increase cooling tower efficiency
Answer: B
Rationale: The bypass ensures minimum flow through chillers to
prevent damage and maintain stable operation.
4. Which HVAC system is most suitable for high-rise buildings with
varying loads?
A. Constant air volume system
B. Packaged terminal air conditioner system
C. Variable air volume system
D. Window air conditioning system
, Answer: C
Rationale: VAV systems efficiently handle varying loads across
multiple zones, making them ideal for high-rise buildings.
5. Heat recovery ventilators primarily function to:
A. Increase refrigeration capacity
B. Transfer heat between exhaust and incoming air streams
C. Remove latent heat only
D. Increase air infiltration rates
Answer: B
Rationale: Heat recovery ventilators transfer sensible and sometimes
latent heat between air streams to improve efficiency.
6. In HVAC design, latent heat refers to:
A. Heat causing temperature change only
B. Heat associated with phase change of moisture
C. Heat from electrical equipment
D. Heat lost through conduction only
Answer: B
Rationale: Latent heat involves energy absorbed or released during
moisture phase changes without temperature change.
7. The function of an economizer cycle is to:
A. Reduce compressor size
B. Use outdoor air for free cooling when conditions permit
C. Increase refrigeration load
, D. Reduce duct static pressure
Answer: B
Rationale: Economizers use favorable outdoor conditions to reduce
mechanical cooling demand.
8. Which component controls refrigerant flow into the evaporator?
A. Compressor
B. Condenser
C. Expansion valve
D. Cooling tower
Answer: C
Rationale: The expansion valve regulates refrigerant flow and
pressure entering the evaporator.
9. Air changes per hour (ACH) is defined as:
A. Air volume per unit floor area
B. Number of times room air is replaced in one hour
C. Supply air temperature changes per hour
D. Fan speed variations per hour
Answer: B
Rationale: ACH measures how frequently the total room air volume is
replaced each hour.
10. A cooling tower primarily removes heat through:
A. Conduction only
B. Evaporation and convection
