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 purpose of an economizer cycle in an HVAC system?
Answer: Use outdoor air for free cooling when conditions allow
An economizer uses outdoor air for cooling when outside conditions are favorable, reducing or eliminating mechanical cooling energy.
A chiller's coefficient of performance (COP) is defined as:
Answer: Cooling output divided by electrical input
COP equals the useful cooling energy output divided by the electrical energy consumed by the chiller.
Which control strategy staggers the start times of multiple HVAC units to reduce peak electrical demand?
Answer: Load shedding / demand limiting
Load shedding or demand limiting staggers equipment startups to avoid simultaneous peak demand spikes on the electric bill.
What does a higher SEER rating indicate for a cooling system?
Answer: Higher seasonal energy efficiency
SEER (Seasonal Energy Efficiency Ratio) measures cooling output over a season divided by electrical energy consumed; higher values mean better efficiency.
In a variable air volume (VAV) system, reducing airflow to 50% of design typically reduces fan energy by approximately:
Answer: 87.5%
Fan power follows the cube law: reducing airflow to 50% reduces power to (0.5)³ = 12.5% of full load, an 87.5% reduction.
Which type of heat exchanger recovers energy between exhaust and supply air streams in an air handling unit?
Answer: Energy recovery ventilator (ERV)
An ERV transfers both sensible heat and latent moisture between exhaust and incoming outdoor air, reducing conditioning loads.
What is the recommended minimum MERV rating for filters in commercial HVAC systems to balance IAQ and energy efficiency?
Answer: MERV 6–8
MERV 6–8 filters provide reasonable IAQ protection without excessive pressure drop that would increase fan energy consumption.