Practice Test Geeks(313D) Residential Air Conditioning Systems Mechanic Certification Practice Test
← All 313D Flashcard Decks

Air Distribution and Ducting Flashcards

7 cards from real 313D practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Air Distribution and Ducting flashcards as text

  1. Which insulation vapor barrier placement is correct for a duct located in a hot, humid unconditioned attic?

    Answer: Vapor barrier on the outside of the insulation facing the attic

    In a hot-humid attic, the vapor barrier must face outward to block moisture from the warm attic air from reaching the cold duct surface.

  2. A duct system uses a trunk-and-branch layout. What is the primary advantage of this design?

    Answer: Simplest to fabricate and requires less material than extended plenum

    Trunk-and-branch systems use a central trunk with smaller branch takeoffs, reducing material compared to running full-size ducts to every outlet.

  3. What does the term 'aspect ratio' refer to in rectangular duct design?

    Answer: Ratio of duct width to duct height

    Aspect ratio is the ratio of a rectangular duct's width to its height; lower ratios (closer to 1:1) are more efficient.

  4. Which type of fire damper is required in a duct penetrating a fire-rated wall and also a smoke barrier?

    Answer: Combination fire/smoke damper

    Where a duct penetrates both a fire-rated wall and a smoke barrier, a combination fire/smoke damper satisfying both requirements must be installed.

  5. When sizing a return air grille, what is the generally recommended face velocity to minimize noise?

    Answer: 300–500 FPM

    Return grilles are typically sized for 300–500 FPM face velocity to keep noise levels acceptable in residential applications.

  6. A technician measures 0.80 inches W.C. total external static pressure on a system rated for 0.50 inches W.C. What corrective action should be taken first?

    Answer: Inspect the duct system for restrictions, undersized ducts, or dirty filters

    Elevated external static pressure most often results from duct restrictions, undersizing, or a clogged filter rather than a blower or refrigerant issue.

  7. What is the function of a balancing damper installed in a branch duct?

    Answer: To throttle airflow to achieve the design CFM for that branch

    Balancing dampers are adjustable devices used to throttle flow in individual branches until design airflow rates are achieved throughout the system.