HVAC and Building Mechanical Systems Flashcards
6 cards from real Building Engineering practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 HVAC and Building Mechanical Systems flashcards as text
What is the function of a heat recovery ventilator (HRV) in a building's HVAC system?
Answer: To transfer heat between exhaust and fresh incoming air streams
An HRV transfers thermal energy from the warm exhaust air to the cool incoming fresh air, reducing heating or cooling energy needed to condition ventilation air.
What ASHRAE standard sets minimum energy efficiency requirements for HVAC systems in commercial buildings?
Answer: ASHRAE 90.1
ASHRAE 90.1 establishes minimum energy efficiency standards for building envelopes, HVAC, lighting, and other systems in commercial facilities.
What is chiller plant delta-T and why is it important?
Answer: The temperature difference between chilled water supply and return — larger delta-T means better efficiency
A larger chilled water delta-T allows more heat to be transported per gallon pumped, reducing pump energy and increasing overall plant efficiency.
What type of expansion device is used in large commercial HVAC systems to meter refrigerant flow precisely?
Answer: Electronic expansion valve (EEV)
Electronic expansion valves use a stepper motor controlled by the system microprocessor to precisely regulate refrigerant flow across a wide range of operating conditions.
What is the purpose of duct pressure testing in HVAC commissioning?
Answer: To verify ducts are airtight and not wasting conditioned air through leakage
Duct leakage testing quantifies air loss through duct seams and joints so corrections can be made before walls are closed, ensuring system delivers design airflow.
What is the purpose of TAB (Testing, Adjusting, and Balancing) in HVAC system commissioning?
Answer: To measure and adjust airflows and water flows to match design specifications
TAB ensures every air outlet and hydronic coil receives the exact design flow rates so each zone achieves specified temperature and ventilation performance.