BPI Heating, Ventilation & Air Conditioning (HVAC) 5 — Questions and Answers
Question 1: What is the purpose of measuring CO in the undiluted flue gas (not ambient air) during a combustion analysis?
- To determine whether the flue pipe is properly sized
- To assess burner performance and identify combustion problems before dilution air masks them (Correct answer)
- To check for gas leaks at the appliance connections
- To verify that the heat exchanger is intact
Correct answer: To assess burner performance and identify combustion problems before dilution air masks them
Measuring CO in undiluted flue gas directly reveals combustion quality at the burner; dilution air in the flue would mask high CO readings if measured downstream.
Question 2: Which condition would cause a heat pump to operate in emergency heat (auxiliary) mode more frequently than expected?
- Thermostat set point changes of less than 2°F
- Low outdoor temperatures causing the heat pump to lose capacity (Correct answer)
- Refrigerant overcharge increasing head pressure
- Duct leakage reducing supply airflow
Correct answer: Low outdoor temperatures causing the heat pump to lose capacity
Heat pumps lose heating capacity as outdoor temperature drops; when capacity falls below the building's heating load, auxiliary (emergency) heat activates to compensate.
Question 3: In a forced-air system, what does high return static pressure typically indicate?
- Oversized supply ducts delivering too much air
- Restricted return air path — undersized returns, dirty filter, or blocked grilles (Correct answer)
- Refrigerant overcharge in the cooling coil
- Excessive combustion air supply to the furnace
Correct answer: Restricted return air path — undersized returns, dirty filter, or blocked grilles
High return static pressure means the air handler is working harder than designed to pull air back from the space, typically caused by undersized returns, a clogged filter, or blocked grilles.
Question 4: What is the difference between sensible heat and latent heat in HVAC applications?
- Sensible heat changes temperature; latent heat changes moisture content without temperature change (Correct answer)
- Sensible heat affects humidity; latent heat affects air temperature
- Sensible heat is measured in grains; latent heat is measured in BTUs
- Sensible heat is removed by the condenser; latent heat is removed by the evaporator only
Correct answer: Sensible heat changes temperature; latent heat changes moisture content without temperature change
Sensible heat causes a measurable temperature change, while latent heat is the energy involved in changing water's phase (evaporation/condensation) without a temperature change.
Question 5: A BPI analyst suspects a gas furnace has a cracked heat exchanger. Which field test provides the most direct evidence?
- Measuring CO in the supply air stream while the furnace fan runs with the burner on (Correct answer)
- Checking manifold gas pressure with a manometer
- Performing a duct blaster test on the supply duct system
- Measuring flue gas temperature with a combustion analyzer
Correct answer: Measuring CO in the supply air stream while the furnace fan runs with the burner on
CO detected in supply air while the burner is firing indicates combustion gases are crossing through a crack in the heat exchanger into the air stream.
Question 6: What does the Seasonal Energy Efficiency Ratio (SEER) represent for air conditioning equipment?
- Cooling output in BTU divided by power input in watts at peak load
- Total seasonal cooling output in BTU divided by total seasonal electricity input in watt-hours (Correct answer)
- The ratio of indoor to outdoor coil surface area
- Equipment efficiency at the AHRI standard rating conditions of 95°F outdoor temperature
Correct answer: Total seasonal cooling output in BTU divided by total seasonal electricity input in watt-hours
SEER is a seasonal metric calculated as total BTUs of cooling divided by total watt-hours of electricity consumed over a typical cooling season, reflecting real-world usage across varying conditions.
Question 7: When installing a supply air register in a bedroom, BPI recommends transfer pathways to ensure which outcome?
- Positive pressure in bedrooms to prevent infiltration
- Return air can flow from closed bedrooms back to the central air handler (Correct answer)
- Supply air velocity is maintained above 400 FPM
- Bedroom doors remain closed at all times during system operation
Correct answer: Return air can flow from closed bedrooms back to the central air handler
Without transfer pathways (jump ducts, door undercuts, transfer grilles), closing bedroom doors pressurizes those rooms and starves the return system, increasing duct leakage problems.
BPI Heating, Ventilation & Air Conditioning (HVAC) 5
What is the purpose of measuring CO in the undiluted flue gas (not ambient air) during a combustion analysis?