FC FC Ductwork & Air Distribution 2 — Questions and Answers
Question 1: What type of duct leakage test measures the total leakage of a duct system at a reference pressure of 25 Pa?
- Blower door test
- Duct blaster (duct pressurization) test (Correct answer)
- Pitot tube traverse
- Anemometer test
Correct answer: Duct blaster (duct pressurization) test
A duct blaster test pressurizes the duct system to 25 Pa and measures airflow required to maintain pressure, quantifying total duct leakage.
Question 2: Flex duct installed with excessive sag will cause which problem?
- Increased duct leakage
- Increased airflow restriction due to liner compression and tight bends (Correct answer)
- Condensation in the duct
- Overheating of the furnace
Correct answer: Increased airflow restriction due to liner compression and tight bends
Sagging flex duct compresses the inner liner, dramatically increasing airflow resistance and reducing delivered CFM to registers.
Question 3: When sealing duct joints and seams, which material is approved by most building codes and SMACNA standards?
- Standard cloth duct tape
- UL 181-rated mastic or foil tape (Correct answer)
- Silicone caulk
- Foam weatherstripping
Correct answer: UL 181-rated mastic or foil tape
UL 181-rated mastic sealant or pressure-sensitive foil tape are code-approved for sealing rigid and flex duct connections.
Question 4: What is the purpose of balancing dampers in a forced-air distribution system?
- To prevent backdrafting in the furnace
- To adjust airflow to individual zones or rooms to achieve comfort balance (Correct answer)
- To prevent duct condensation
- To reduce duct static pressure overall
Correct answer: To adjust airflow to individual zones or rooms to achieve comfort balance
Balancing dampers allow technicians to restrict airflow to over-supplied areas and redirect it to under-supplied rooms.
Question 5: Supply registers in a forced-air system are typically located near which area for best comfort in heating climates?
- High on interior walls
- Near the ceiling on interior walls
- Low on exterior walls under windows (Correct answer)
- In the center of the room ceiling
Correct answer: Low on exterior walls under windows
Placing supply registers low on exterior walls under windows counteracts cold downdrafts and creates an even floor-to-ceiling temperature.
Question 6: What is the minimum R-value required by most US energy codes for ducts located in unconditioned attic spaces?
- R-4
- R-6
- R-8 (Correct answer)
- R-11
Correct answer: R-8
Most current US energy codes (IECC) require a minimum of R-8 insulation for ducts in unconditioned attic spaces.
FC FC Ductwork & Air Distribution 2
What type of duct leakage test measures the total leakage of a duct system at a reference pressure of 25 Pa?