HVAC Systems and Controls Flashcards
7 cards from real Certified Energy Auditor Certification practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 HVAC Systems and Controls flashcards as text
What is the primary energy disadvantage of a constant volume reheat HVAC system?
Answer: Simultaneous heating and cooling waste energy
Constant volume reheat systems cool all air to a low temperature then reheat it for zones needing less cooling, wasting both cooling and heating energy.
A building automation system (BAS) data point showing 'chiller plant delta-T' refers to:
Answer: Temperature difference between entering and leaving chilled water
Chilled water delta-T is the difference between the chilled water return temperature and supply temperature, which indicates how effectively the distribution system is transferring heat.
What is the purpose of a cooling tower bypass valve in a chilled water plant?
Answer: Prevent freezing of cooling tower fill in cold weather
A bypass valve diverts warm condenser water around the cooling tower during cold weather to prevent the tower from freezing and to maintain minimum condenser water temperatures.
When auditing a pneumatic control system for energy savings opportunities, the auditor should look for:
Answer: Opportunities to convert to direct digital controls (DDC)
Pneumatic controls are typically less precise and flexible than DDC systems; conversion to DDC often enables advanced strategies like optimal start, reset schedules, and better diagnostics.
Which HVAC system type is generally most efficient for buildings with highly variable zone loads?
Answer: Variable air volume (VAV) with DDC controls
VAV systems with DDC controls modulate airflow to match zone loads, saving significant fan and conditioning energy compared to constant volume approaches.
What does 'simultaneous heating and cooling' fault detection identify in a BAS?
Answer: A zone where heating and cooling systems are operating at the same time
Simultaneous heating and cooling is a common energy waste where a zone's heating and cooling operate concurrently, often due to control sequencing errors or faulty sensors.
In evaluating HVAC efficiency, what does a low condenser approach temperature in a chiller indicate?
Answer: Clean condenser tubes with good heat transfer
A low approach temperature (small difference between condenser water leaving temperature and refrigerant condensing temperature) indicates clean tubes and efficient heat transfer.