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Energy Efficiency Flashcards

7 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 7 Energy Efficiency flashcards as text

  1. What is the primary energy efficiency advantage of a two-stage compressor over a single-stage unit?

    Answer: It operates at reduced capacity during mild conditions, consuming less energy

    Two-stage compressors can run at lower capacity during mild weather, matching actual load and reducing energy consumption compared to a single-stage unit cycling on and off.

  2. Which type of duct leakage has the greatest negative impact on HVAC efficiency?

    Answer: Supply duct leakage into unconditioned spaces

    Supply duct leakage into unconditioned spaces (like attics or crawlspaces) directly wastes conditioned air that never reaches the occupied space, causing significant energy loss.

  3. What is the significance of the AHRI 210/240 test standard for residential HVAC equipment?

    Answer: It establishes the test conditions used to measure and rate cooling and heating efficiency (SEER2, HSPF2)

    AHRI 210/240 defines the standardized test conditions and procedures used to rate residential unitary HVAC equipment efficiency, ensuring consistent manufacturer comparisons.

  4. A geothermal heat pump has a much higher COP than an air-source heat pump in winter. Why?

    Answer: Ground temperatures remain relatively stable year-round, providing a more favorable heat source than cold outdoor air

    Ground temperatures at depth stay near 50–55°F year-round, giving geothermal heat pumps a much warmer heat source than outdoor air during cold winters, greatly improving COP.

  5. What does 'integrated part load value' (IPLV) measure for commercial chillers?

    Answer: Weighted average efficiency across multiple part-load operating points to reflect real-world performance

    IPLV is a weighted average of chiller efficiency at 100%, 75%, 50%, and 25% loads, better representing annual energy use than full-load efficiency alone.

  6. Which control strategy best reduces energy use in a multi-zone VAV system?

    Answer: Supply air temperature reset based on zone demand

    Resetting supply air temperature upward when cooling loads are low reduces refrigeration energy and allows VAV boxes to open wider, lowering fan energy simultaneously.

  7. How do low-e window coatings contribute to HVAC energy efficiency?

    Answer: They reflect infrared radiation, reducing solar heat gain in summer and heat loss in winter

    Low-e coatings selectively reflect long-wave infrared radiation, reducing unwanted solar heat gain in summer and slowing heat escape through windows in winter.