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.
