HVAC Ventilation and Air Distribution 1 — Questions and Answers
Question 1: What unit is used to measure airflow volume in HVAC duct systems?
- PSI (pounds per square inch)
- CFM (cubic feet per minute) (Correct answer)
- FPM (feet per minute)
- BTU/hr (British Thermal Units per hour)
Correct answer: CFM (cubic feet per minute)
CFM (cubic feet per minute) is the standard unit for measuring volumetric airflow in HVAC duct systems and ventilation equipment.
Question 2: What is static pressure in an HVAC duct system?
- The velocity pressure of moving air
- The resistance to airflow within the duct system (Correct answer)
- The pressure difference between supply and return ducts
- The fan speed setting
Correct answer: The resistance to airflow within the duct system
Static pressure is the resistance to airflow caused by friction and fittings in the duct system, measured in inches of water column (in. WC).
Question 3: What does ASHRAE Standard 62.2 specify?
- Duct leakage testing requirements
- Ventilation requirements for acceptable indoor air quality in residential buildings (Correct answer)
- Energy efficiency ratings for HVAC equipment
- Refrigerant handling and recovery procedures
Correct answer: Ventilation requirements for acceptable indoor air quality in residential buildings
ASHRAE 62.2 sets the minimum ventilation rates and indoor air quality requirements for residential buildings in the United States.
Question 4: What is the purpose of a manual balancing damper in an air distribution system?
- To automatically adjust airflow based on thermostat demand
- To manually adjust airflow to individual zones or branches to achieve proper balance (Correct answer)
- To prevent backdraft from outdoor air
- To control the speed of the supply fan
Correct answer: To manually adjust airflow to individual zones or branches to achieve proper balance
Manual balancing dampers allow technicians to restrict airflow to over-supplied zones and redirect it to under-supplied zones to achieve proper air distribution balance.
Question 5: What type of ventilation system uses both a supply fan and an exhaust fan to control building pressure?
- Natural ventilation
- Exhaust-only ventilation
- Supply-only ventilation
- Balanced ventilation (Correct answer)
Correct answer: Balanced ventilation
A balanced ventilation system uses equal supply and exhaust airflow to maintain neutral building pressure, which is the design goal for most commercial HVAC systems.
Question 6: What device is used to recover heat from exhaust air and transfer it to incoming fresh air in an energy recovery system?
- Economizer
- Heat Recovery Ventilator (HRV) or Energy Recovery Ventilator (ERV) (Correct answer)
- Variable Air Volume (VAV) box
- Fan-powered mixing box
Correct answer: Heat Recovery Ventilator (HRV) or Energy Recovery Ventilator (ERV)
An HRV or ERV transfers heat (and moisture in the case of an ERV) between exhaust air and incoming fresh air to recover energy that would otherwise be wasted.
HVAC Ventilation and Air Distribution 1
What unit is used to measure airflow volume in HVAC duct systems?