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ASHRAE Air Distribution System Design 200 Practice Exam Questions Questions 1–25: Fundamentals of Air Distribution Systems Question 1 Which of the following best describes the primary purpose of an air distribution system in HVAC design?
- A) To generate conditioned air at the source
- B) To transport refrigerant between components
- C) To deliver conditioned air effectively to occupied spaces
- D) To eliminate the need for ventilation air Answer: C Explanation: The primary purpose of an air distribution system is to deliver conditioned air efficiently and uniformly to occupied spaces while maintaining comfort and indoor air quality.
Question 2 Room air distribution systems are primarily intended to achieve which of the following objectives?
- A) Minimize building construction costs
- B) Provide thermal comfort and ventilation for space occupants and processes
- C) Maximize air velocity throughout the occupied space
- D) Eliminate the need for mechanical cooling Answer: B
Explanation: Room air distribution systems are intended to provide thermal comfort and ventilation for space occupants and processes.
Question 3 Which of the following is NOT a basic performance mandate for an HVAC system according to ASHRAE?
- A) Acceptable indoor air temperature
- B) Air movement
- C) Humidity control
- D) Building structural integrity Answer: D Explanation: The four basic performance mandates for an HVAC system are acceptable indoor air temperature, air movement, humidity, and quality.
Question 4 Which principle is most critical in minimizing duct system energy losses?
- A) Increasing duct color contrast
- B) Reducing duct length and leakage
- C) Increasing fan horsepower
- D) Maximizing diffuser quantity Answer: B
Explanation: Chapter 20 in the ASHRAE Handbook—HVAC Systems and Equipment describes the characteristics of various air inlets, outlets, fan-coil units, chilled beams, air curtain units, and terminal units, as well as selection tools and guidelines.
Question 7 Which ASHRAE Technical Committee is concerned with the distribution, diffusion, and conditioning of air within rooms?
- A) TC 4.3 – Ventilation Requirements and Infiltration
- B) TC 5.3 – Room Air Distribution
- C) TC 6.3 – Central Forced Air Heating and Cooling Systems
- D) TC 8.3 – Absorption and Heat Pump Systems Answer: B Explanation: TC 5.3 is concerned with the distribution, diffusion, and conditioning of air within rooms and similarly treated spaces.
Question 8 What is the primary difference between mixed systems and fully stratified systems in room air distribution?
- A) Mixed systems produce little or no thermal stratification; fully stratified systems produce little or no mixing within the occupied space
- B) Mixed systems are only used for heating; fully stratified systems are only used for cooling
- C) Mixed systems require higher airflow than fully stratified systems
- D) There is no difference between the two system types
Answer: A Explanation: Mixed systems produce little or no thermal stratification of air within the space. Fully (thermally) stratified systems produce little or no mixing of air within the occupied space.
Question 9 Which of the following is an example of a fully stratified air distribution system?
- A) Overhead air distribution with ceiling supply
- B) Thermal displacement ventilation
- C) Underfloor air distribution with floor diffusers
- D) Task/ambient conditioning systems Answer: B Explanation: Thermal displacement ventilation is an example of a fully (thermally) stratified system that produces little or no mixing of air within the occupied space.
Question 10 Which of the following is an example of a partially mixed air distribution system?
- A) Overhead air distribution
- B) Thermal displacement ventilation
- C) Underfloor air distribution
- D) Natural ventilation
Answer: B Explanation: The amount of stratification in the room is primarily determined by the balance between total room airflow and heat load.
Question 13 Which of the following is a major factor affecting room supply airflow characteristics?
- A) The type of furniture in the room
- B) Total room supply airflow quantity
- C) The color of the diffusers
- D) The age of the building Answer: B Explanation: Major factors for room supply airflow include total room supply airflow quantity, room supply air temperature, diffuser type, and diffuser throw height.
Question 14 For room heat loads, which of the following is NOT a major factor?
- A) Magnitude and number of loads in space
- B) Load type (point or distributed source)
- C) Elevation of load
- D) The color of the heat source
Answer: D Explanation: Major factors for room heat loads include magnitude and number of loads, load type, elevation of load, radiative/convective split, and whether pollutants are associated with heat sources.
Question 15 What is the relationship between local temperature and carbon dioxide (CO2) concentration profiles in stratified air distribution systems?
- A) They have opposite profiles
- B) They have similar stratification profiles
- C) There is no relationship
- D) CO2 concentration is always uniform regardless of temperature Answer: B Explanation: Local temperature and carbon dioxide (CO2) concentration have similar stratification profiles.
Question 16 Which of the following best describes the function of an air terminal (inlet or outlet) in a room air distribution system?
- A) To generate conditioned air
- B) To introduce or remove air from a conditioned space
- C) To filter the air before distribution
Answer: B Explanation: Chapter 57 provides a discussion of various air distribution strategies, tools, and guidelines for design and application.
Question 19 For naturally ventilated spaces, which ASHRAE Handbook chapter should be referenced?
- A) Chapter 16 of the ASHRAE Handbook—Fundamentals
- B) Chapter 20 of the ASHRAE Handbook—HVAC Systems and Equipment
- C) Chapter 57 of the ASHRAE Handbook—HVAC Applications
- D) Chapter 48 of the ASHRAE Handbook—HVAC Applications Answer: A Explanation: For information on naturally ventilated spaces, see Chapter 16 of the ASHRAE Handbook—Fundamentals.
Question 20 What is the primary disadvantage of high-velocity air distribution systems?
- A) Lower energy consumption
- B) Reduced duct size requirements
- C) Increased noise levels
- D) Improved air quality
Answer: C Explanation: High-velocity systems often generate increased noise and require more sound attenuation measures.
Question 21 Which duct design method assumes equal pressure loss per unit length of duct?
- A) Static regain method
- B) Equal friction method
- C) Velocity reduction method
- D) Total pressure method Answer: B Explanation: The equal friction method designs duct systems so that pressure loss per unit length remains constant throughout the system.
Question 22 In the context of air distribution systems, what is "zone ventilation efficiency" as defined by ASHRAE 62.1?
- A) The efficiency of the air handling unit fan
- B) The efficiency with which a system distributes outdoor air from the intake to an individual breathing zone
- C) The efficiency of the air filters in removing contaminants
- D) The efficiency of the duct insulation
Answer: C Explanation: The ASHRAE guideline stipulates an ADPI of 80% as the minimum acceptable level for cooling loads up to 250 W/m².
Question 25 Cold air distribution systems require special design considerations because:
- A) They use less energy than conventional systems
- B) Cooled surfaces must be well insulated and sealed to prevent condensation
- C) They require larger duct sizes
- D) They cannot be used in commercial buildings Answer: B Explanation: Cold air distribution system design considerations include that cooled surfaces shall be well insulated and sealed to prevent condensation.
Questions 26–50: Duct Design Methods
Question 26 Which duct design method is considered a preferred method for larger, medium to high velocity supply air systems?
- A) Equal friction method
- B) Static regain method
- C) Velocity reduction method
- D) Constant velocity method Answer: B Explanation: The static regain method is a preferred method for larger, medium to high velocity supply air systems.
Question 27 In the static regain method, how are duct sections sized?
- A) Each duct section is sized such that the regain occurring at the entrance of the duct section is approximately equal to the static pressure loss for the duct section
- B) All duct sections are sized to have the same velocity
- C) Duct sections are sized based on the highest pressure drop
- D) Duct sections are sized to minimize material cost only Answer: A Explanation: Each duct section is sized such that the regain occurring at the entrance of the duct section is approximately equal to the static pressure loss for the duct section.
Question 28 In the equal friction method, what is the typical default pressure loss per unit length?
- A) 0.05 in-wg/100 ft
- B) 0.10 in-wg/100 ft
- C) Calculate the total pressure drop for each branch
- D) Select the smallest possible duct size Answer: B Explanation: In the static regain method, the duct size at the fan is selected using the friction chart to get the starting velocity. Other main ducts are then sized to achieve static regain from section to section.
Question 31 Which of the following is a duct sizing method mentioned in ASHRAE design guidelines?
- A) Velocity reduction method
- B) Temperature reduction method
- C) Pressure increase method
- D) Flow acceleration method Answer: A Explanation: Duct sizing methods include equal friction, static regain, equal velocity, and velocity reduction (also known as velocity method).
Question 32 The equal friction method calculates duct size based on:
- A) The initial friction loss rate
- B) The final velocity at the outlet
- C) The total static pressure available
- D) The temperature of the air Answer: A Explanation: The equal friction method calculates the duct size based on the initial friction loss rate.
Question 33 In the static regain design approach, main ducts and branches are sized to achieve:
- A) Maximum air velocity
- B) Minimum material cost
- C) A balanced pressure loss from section to section
- D) Equal air temperature throughout Answer: C Explanation: In the static regain design approach, main ducts and branches are then sized to achieve a balanced pressure loss from section to section.
Question 34 What is the primary advantage of the static regain method over the equal friction method?
- A) It requires less duct material
- B) It provides better pressure balance in the system
- C) It is simpler to calculate
Answer: B Explanation: The equal friction method is commonly used for low-velocity, low-pressure duct systems due to its simplicity.
Question 37 What is the relationship between duct size and friction loss in the equal friction method?
- A) Larger ducts have higher friction loss per unit length
- B) Smaller ducts have higher friction loss per unit length
- C) Duct size has no effect on friction loss
- D) Friction loss is independent of duct size Answer: B Explanation: In the equal friction method, smaller ducts have higher friction loss per unit length, and duct sizes are selected to maintain a constant friction loss rate.
Question 38 The static regain method is particularly suitable for:
- A) Residential duct systems
- B) Larger, medium to high velocity supply air systems
- C) Low-velocity exhaust systems
- D) Small office buildings
Answer: B Explanation: The static regain method is a preferred method for larger, medium to high velocity supply air systems.
Question 39 In duct design, what does "regain" refer to in the static regain method?
- A) The recovery of static pressure as velocity decreases in a duct section
- B) The increase in air temperature in the duct
- C) The decrease in air density in the duct
- D) The increase in air velocity in the duct Answer: A Explanation: Regain refers to the recovery of static pressure as air velocity decreases when a duct section expands in size.
Question 40 What is the typical range of static pressure in low-pressure duct systems?
- A) 0-1 in. w.g.
- B) 1-2 in. w.g.
- C) 2-4 in. w.g.
- D) 4-6 in. w.g. Answer: A
