Air Distribution Flashcards
6 cards from real NATE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Air Distribution flashcards as text
What unit is used to measure duct air leakage during a duct leakage test?
Answer: CFM25 (cubic feet per minute at 25 pascals)
Duct leakage is expressed as CFM25, the airflow escaping through duct leaks when pressurized to 25 pascals above atmospheric pressure.
What is the recommended duct sealing material for permanent duct repairs?
Answer: Mastic sealant or metal foil tape (UL 181 listed)
Mastic sealant and UL 181 listed foil tape are durable, code-approved methods; standard cloth duct tape dries out and fails over time.
What MERV rating range is recommended for residential HVAC filters to balance filtration and airflow?
Answer: 5–8
MERV 5–8 filters provide adequate filtration for residential equipment while maintaining sufficient airflow and avoiding excessive pressure drop.
What is the purpose of a plenum in an HVAC duct system?
Answer: Serve as a pressure chamber that distributes or collects air from multiple duct branches
The supply plenum distributes conditioned air from the air handler to multiple duct branches; the return plenum collects air from return branches.
What is the maximum recommended duct velocity for residential supply ducts to minimize noise?
Answer: 700–900 FPM
Residential supply ducts typically target 700–900 FPM to balance duct size with acceptable noise levels.
What is the effect of duct leakage in unconditioned spaces like attics and crawlspaces?
Answer: Wastes significant conditioned air to outside, dramatically increasing energy consumption and reducing comfort
Leaking supply ducts in unconditioned spaces lose conditioned air to outside while leaking return ducts pull hot/cold unconditioned air into the system.