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Ventilation and Air Distribution Flashcards

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

Read the first 6 Ventilation and Air Distribution flashcards as text

  1. What is the purpose of a return air plenum in an HVAC system?

    Answer: To collect air from the conditioned space and return it to the air handler

    The return air plenum is the low-pressure chamber or duct that collects air from the conditioned space and returns it to the air handling unit for reconditioning.

  2. What does 'negative building pressure' mean and why is it problematic?

    Answer: Indoor air pressure is lower than outdoor air pressure, causing uncontrolled infiltration of unconditioned air

    Negative building pressure means the indoor air pressure is lower than outdoors, pulling in uncontrolled outside air (infiltration) through cracks and openings, which wastes energy and can cause moisture problems.

  3. What is the primary purpose of a mixing box or outside air damper on an air handling unit?

    Answer: To introduce a controlled amount of outdoor fresh air into the return air stream

    The outside air damper and mixing box introduce a controlled quantity of fresh outdoor air into the return air stream to meet ventilation requirements per ASHRAE standards.

  4. What does 'commissioning' an HVAC system involve?

    Answer: Verifying that the installed system meets design specifications through testing and balancing

    Commissioning is the systematic process of verifying that all HVAC components and systems are installed, operated, and balanced to meet design intent and owner requirements.

  5. What is the function of a ceiling plenum return system in commercial buildings?

    Answer: It uses the space above the dropped ceiling as a return air pathway instead of ducted returns

    A plenum return system uses the ceiling cavity above a suspended ceiling as an open return air pathway back to the AHU, eliminating the need for return air ductwork.

  6. What is 'air balancing' and when is it performed?

    Answer: Adjusting airflow to each zone/room to match design specifications, performed at system startup and commissioning

    Air balancing is the process of measuring and adjusting airflow throughout the duct system so each space receives its design CFM, ensuring proper comfort and efficiency.