Practice Test Geeks(313D) Residential Air Conditioning Systems Mechanic Certification Practice Test
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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. What is the primary reason duct leakage in an attic is more detrimental than duct leakage in a conditioned basement?

    Answer: Leakage into unconditioned attic space is a complete energy loss, while basement leakage stays within the thermal envelope

    Air leaking into an unconditioned attic is permanently lost from the system, whereas leakage into a conditioned basement still benefits the space.

  2. Which method is used to test residential duct leakage to outside (duct leakage to outdoors)?

    Answer: Blower door test with duct registers taped

    Sealing all duct registers and pressurizing with a duct blaster while using a blower door measures how much duct leakage communicates with the outdoors.

  3. What happens to airflow velocity when a duct transitions from a smaller to a larger cross-section?

    Answer: Velocity decreases and static pressure partially recovers

    When a duct expands, the air slows down (by continuity) and some velocity pressure converts back to static pressure—this is called static regain.

  4. A supply diffuser produces a draft complaint even though the CFM is correct. What adjustment is most appropriate?

    Answer: Adjust the diffuser deflection vanes to redirect airflow toward the ceiling

    Redirecting the diffuser vanes to throw air along the ceiling surface uses the Coanda effect to keep the air stream from dropping into the occupied zone.

  5. What duct material is NOT recommended for use in return air systems because it can off-gas harmful compounds when exposed to the airstream?

    Answer: Asbestos-containing duct insulation

    Asbestos-containing duct insulation is prohibited because asbestos fibers can be entrained in the airstream and inhaled by occupants.

  6. When a duct passes through an unconditioned space, the minimum insulation R-value required by most US energy codes is:

    Answer: R-8

    IECC and most state energy codes require a minimum of R-8 insulation on ducts located in unconditioned spaces such as attics and crawlspaces.

  7. What is the purpose of an equalizer leg installed on a plenum near the air handler outlet?

    Answer: To distribute air velocity evenly before it enters branch takeoffs

    An equalizer leg allows turbulent, high-velocity air from the blower to straighten and slow before encountering branch takeoffs, improving distribution.