HERS HVAC System Evaluation 2 — Questions and Answers
Question 1: When performing a HERS duct leakage test, what does 'Total Duct Leakage' measure?
- Leakage from supply ducts only
- Combined leakage from both supply and return ducts to outside and inside conditioned space (Correct answer)
- Leakage from return ducts only
- Only the leakage that goes directly to the outdoors
Correct answer: Combined leakage from both supply and return ducts to outside and inside conditioned space
Total duct leakage measures combined air loss from both supply and return ducts, including leakage to unconditioned spaces and outside.
Question 2: Which RESNET standard defines the protocol for HVAC system testing in HERS ratings?
- RESNET/ICC 380 (Correct answer)
- RESNET Publication 12
- ACCA Manual D
- ASHRAE 62.2
Correct answer: RESNET/ICC 380
RESNET/ICC 380 is the standard that establishes test methods for building envelope and HVAC systems used in HERS ratings.
Question 3: A home has a heat pump with a HSPF of 8.2. What does HSPF measure?
- Cooling efficiency in mixed climates
- Heating season performance in BTUs per watt-hour (Correct answer)
- Annual energy factor for hot water heating
- Seasonal energy efficiency ratio for cooling
Correct answer: Heating season performance in BTUs per watt-hour
HSPF (Heating Seasonal Performance Factor) measures a heat pump's heating efficiency as total BTUs delivered per watt-hour consumed over a heating season.
Question 4: During a HERS inspection, a rater finds that supply registers are located in the floor of a vented crawlspace. What is the primary energy concern?
- The registers may not deliver enough airflow velocity
- Ducts in unconditioned crawlspaces are subject to thermal losses and infiltration (Correct answer)
- Floor registers are prohibited by ASHRAE 62.2
- The system cannot be balanced properly with floor registers
Correct answer: Ducts in unconditioned crawlspaces are subject to thermal losses and infiltration
Ducts running through unconditioned crawlspaces lose conditioned air to thermal conduction and duct leakage, significantly reducing system efficiency.
Question 5: What is the minimum SEER2 rating required for a central air conditioner to qualify as efficient under current federal standards (effective 2023)?
- 13 SEER2 in northern states, 14 SEER2 in southern states
- 15 SEER2 nationally
- 14 SEER2 in northern states, 15 SEER2 in southern states (Correct answer)
- 12 SEER2 nationally
Correct answer: 14 SEER2 in northern states, 15 SEER2 in southern states
As of January 1, 2023, the federal minimum efficiency is 14 SEER2 for the North region and 15 SEER2 for the South and Southwest regions.
Question 6: A HERS rater is evaluating refrigerant charge on a split-system AC. Which field verification method is most commonly referenced in RESNET guidelines?
- Weighing the refrigerant cylinder before and after charging
- Superheat or subcooling measurement at the outdoor unit (Correct answer)
- Monitoring compressor amperage draw
- Visual inspection of the suction line for frost
Correct answer: Superheat or subcooling measurement at the outdoor unit
RESNET references superheat (for fixed-orifice systems) or subcooling (for TXV systems) measurement as the standard field method to verify proper refrigerant charge.
Question 7: In ACCA Manual J load calculations used for HERS ratings, what does the 'design temperature difference' refer to?
- The difference between supply and return air temperatures
- The gap between indoor design temperature and outdoor design dry-bulb temperature (Correct answer)
- The delta-T across the heat exchanger
- The allowable thermostat setpoint variation
Correct answer: The gap between indoor design temperature and outdoor design dry-bulb temperature
Design temperature difference is the gap between the desired indoor temperature (typically 70°F) and the local outdoor design dry-bulb temperature used to size HVAC equipment.
HERS HVAC System Evaluation 2
When performing a HERS duct leakage test, what does 'Total Duct Leakage' measure?