Certified Energy Auditor Certification HVAC Systems and Performance 2 — Questions and Answers
Question 1: What does the Energy Efficiency Ratio (EER) measure in a cooling system?
- BTU of cooling output per watt of electrical input at a fixed condition (Correct answer)
- Seasonal average efficiency across varying temperatures
- Ratio of sensible to latent heat removal
- Compressor displacement volume per unit of refrigerant
Correct answer: BTU of cooling output per watt of electrical input at a fixed condition
EER is the ratio of cooling capacity in BTU/hr to power input in watts at a single standard test condition (95°F outdoor, 80°F/67°F indoor).
Question 2: In a variable air volume (VAV) system, what component modulates airflow to individual zones?
- Economizer damper
- VAV terminal box with damper (Correct answer)
- Supply fan bypass valve
- Chilled water control valve
Correct answer: VAV terminal box with damper
A VAV terminal box contains a damper that modulates to deliver the airflow required to maintain zone setpoint temperature.
Question 3: A chiller's condenser water leaving temperature is 90°F. Lowering it to 85°F will most likely have what effect on chiller efficiency?
- Efficiency decreases due to higher lift
- Efficiency improves because condenser pressure drops (Correct answer)
- No change because chiller kW is fixed
- Efficiency decreases due to increased refrigerant flow
Correct answer: Efficiency improves because condenser pressure drops
Reducing condenser water temperature lowers condensing pressure, reducing compressor work and improving chiller kW/ton.
Question 4: Which ASHRAE Standard defines energy efficiency requirements for commercial HVAC equipment?
- ASHRAE 62.1
- ASHRAE 90.1 (Correct answer)
- ASHRAE 55
- ASHRAE 189.1
Correct answer: ASHRAE 90.1
ASHRAE 90.1, 'Energy Standard for Buildings Except Low-Rise Residential Buildings,' sets minimum efficiency requirements for HVAC, lighting, and envelope.
Question 5: What is the primary purpose of a heat recovery ventilator (HRV) in a building?
- Recover heat from exhaust air to pre-condition incoming fresh air (Correct answer)
- Recirculate return air to reduce heating load
- Boost supply fan static pressure during peak demand
- Remove latent heat from condenser water
Correct answer: Recover heat from exhaust air to pre-condition incoming fresh air
An HRV transfers heat from exhaust air to incoming outdoor air, reducing the energy needed to condition fresh ventilation air.
Question 6: A rooftop unit shows a 15°F temperature split across the evaporator coil instead of the expected 20°F. What is the most likely cause?
- Oversized duct system increasing airflow
- Low refrigerant charge (Correct answer)
- High outdoor humidity raising dew point
- Condenser coil fouling
Correct answer: Low refrigerant charge
Low refrigerant charge reduces the refrigerant mass available to absorb heat, lowering the evaporator's cooling capacity and temperature split.
Question 7: Which metric best describes the seasonal performance of a heat pump in heating mode?
- EER
- SEER
- HSPF (Correct answer)
- COP at ARI 210/240
Correct answer: HSPF
Heating Seasonal Performance Factor (HSPF) measures total BTU of heat delivered divided by total watt-hours consumed over a heating season.
Certified Energy Auditor Certification HVAC Systems and Performance 2
What does the Energy Efficiency Ratio (EER) measure in a cooling system?