HVAC Load Calculation and System Design 2 — Questions and Answers
Question 1: What does SEER (Seasonal Energy Efficiency Ratio) measure for air conditioning equipment?
- The instantaneous efficiency at peak load conditions
- The seasonal cooling efficiency ratio of cooling output to electrical input over a cooling season (Correct answer)
- The ratio of supply air to return air in the system
- The solar heat gain efficiency of the building envelope
Correct answer: The seasonal cooling efficiency ratio of cooling output to electrical input over a cooling season
SEER measures the total cooling output of an AC system divided by the total electrical energy consumed over a typical cooling season, with higher SEER indicating greater efficiency.
Question 2: What is the minimum SEER2 rating required for new central AC systems in the US southern region as of 2023?
- 13 SEER2
- 14 SEER2 (Correct answer)
- 15 SEER2
- 16 SEER2
Correct answer: 14 SEER2
As of January 1, 2023, the DOE mandates a minimum of 14 SEER2 (equivalent to approximately 15 SEER) for new split-system central air conditioners in the US Southeast and Southwest regions.
Question 3: What factor is NOT included in a Manual J residential load calculation?
- Window size and orientation
- Insulation R-values in walls and ceilings
- Homeowner's preferred thermostat settings (Correct answer)
- Number of occupants and internal heat gains
Correct answer: Homeowner's preferred thermostat settings
Manual J calculates loads based on physical building characteristics and design weather data, not personal preferences like preferred thermostat settings.
Question 4: What is a Manual D calculation used for in residential HVAC?
- Sizing the heating and cooling equipment
- Designing the duct system for proper airflow distribution (Correct answer)
- Calculating the refrigerant charge for the system
- Determining the ventilation requirements
Correct answer: Designing the duct system for proper airflow distribution
Manual D (by ACCA) is the standard procedure for designing residential duct systems to deliver the correct CFM to each room at acceptable static pressures.
Question 5: What is 'right-sizing' of HVAC equipment and why is it important?
- Installing the most powerful unit available to ensure comfort on the hottest day
- Sizing equipment to match the calculated load, avoiding both over- and under-sizing (Correct answer)
- Selecting the smallest unit that fits the mechanical room space
- Choosing equipment based on price per ton rather than load calculations
Correct answer: Sizing equipment to match the calculated load, avoiding both over- and under-sizing
Right-sizing means selecting equipment whose capacity closely matches the calculated building load to ensure efficient operation, proper humidity control, and long equipment life.
Question 6: What is the significance of the 'heat gain through glass' component in a summer cooling load?
- It is usually the smallest load component and can be ignored
- Solar heat gain through windows is often the largest component of a building's summer cooling load (Correct answer)
- It only affects east-facing windows in the morning
- It is already included in the U-factor calculation for windows
Correct answer: Solar heat gain through windows is often the largest component of a building's summer cooling load
Solar heat gain through glazing is typically one of the largest contributors to summer cooling load, making window orientation, size, and shading critical design considerations.
HVAC Load Calculation and System Design 2
What does SEER (Seasonal Energy Efficiency Ratio) measure for air conditioning equipment?