Practice Test Geeks(313D) Residential Air Conditioning Systems Mechanic Certification Practice Test
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Psychrometrics and Humidity Control 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 Psychrometrics and Humidity Control flashcards as text

  1. What does the Sensible Heat Ratio (SHR) of a cooling system represent?

    Answer: The ratio of sensible heat removal to total heat removal (sensible plus latent)

    SHR = sensible load ÷ (sensible load + latent load), indicating what fraction of total cooling capacity handles temperature reduction versus dehumidification.

  2. What happens to relative humidity when air temperature increases while the moisture content stays the same?

    Answer: Relative humidity decreases because warmer air can hold more moisture

    As temperature rises, the moisture-holding capacity of air increases, so with unchanged absolute moisture content the relative humidity (a ratio) decreases.

  3. What is the primary function of a humidistat in a residential HVAC system?

    Answer: To sense indoor relative humidity and signal the system to humidify or dehumidify

    A humidistat detects relative humidity and cycles humidification or dehumidification equipment to maintain the set humidity level, functioning like a thermostat but for moisture.

  4. How many grains of moisture are in one pound of water?

    Answer: 7,000 grains

    There are exactly 7,000 grains per pound of water; HVAC technicians express air moisture content in grains per pound (GPP) of dry air.

  5. Under what condition does condensation form on interior window surfaces?

    Answer: When the window surface temperature drops below the dew point of the indoor air

    Condensation forms on any surface whose temperature falls below the dew point of the surrounding air, regardless of a single fixed RH percentage.

  6. What does a high latent load in a residential building indicate?

    Answer: There is significant moisture that the cooling system must condense and remove

    A high latent load means large amounts of moisture — from occupants, infiltration, cooking, or plants — are entering the space and must be removed by the AC system.

  7. What is the bypass factor of a cooling coil?

    Answer: The fraction of airflow that passes through the coil without making effective thermal contact

    Bypass factor is the fraction of air that passes through the coil without meaningfully contacting the coil surface, reducing cooling and dehumidification effectiveness.