BPI HVAC Systems 2 — Questions and Answers
Question 1: What does the ACCA Manual J calculation determine for a residential building?
- Duct sizing requirements
- Heating and cooling load (Correct answer)
- Equipment efficiency rating
- Ventilation airflow rates
Correct answer: Heating and cooling load
Manual J is the industry-standard protocol for calculating a home's heating and cooling loads, which determines the required equipment capacity.
Question 2: Which condition indicates that a heat pump is operating in defrost mode?
- Indoor unit blowing cold air briefly
- Outdoor fan stops and reversing valve cycles (Correct answer)
- Thermostat set point is overridden
- Refrigerant pressure drops below normal
Correct answer: Outdoor fan stops and reversing valve cycles
During defrost, the outdoor fan stops and the reversing valve shifts to move hot refrigerant to the outdoor coil to melt accumulated frost.
Question 3: In a forced-air system, what is the primary purpose of a return air plenum?
- Filter combustion air for the furnace
- Collect and route return air to the air handler (Correct answer)
- Distribute conditioned air to rooms
- House the expansion valve assembly
Correct answer: Collect and route return air to the air handler
The return air plenum collects air from return ducts throughout the home and channels it back to the air handler for reconditioning.
Question 4: A homeowner reports that their central air conditioner runs continuously but never reaches the set temperature on very hot days. What is the MOST likely cause?
- Undersized equipment for the cooling load (Correct answer)
- Dirty evaporator coil only
- Refrigerant overcharge
- Thermostat calibration error
Correct answer: Undersized equipment for the cooling load
An air conditioner that runs continuously without satisfying the thermostat on design-temperature days is typically undersized for the building's actual cooling load.
Question 5: What does a high static pressure reading across the air filter indicate in an HVAC system?
- Adequate airflow through the system
- Filter is loaded and restricting airflow (Correct answer)
- Return ducts are oversized
- Blower motor is operating at peak speed
Correct answer: Filter is loaded and restricting airflow
Elevated pressure drop across a filter indicates it has collected enough particulate to significantly restrict airflow through the system.
Question 6: Which type of ventilation strategy uses the stack effect and wind to move air through a building without mechanical assistance?
- Balanced ventilation
- Natural ventilation (Correct answer)
- Exhaust-only ventilation
- Supply-only ventilation
Correct answer: Natural ventilation
Natural ventilation relies on buoyancy-driven stack effect and wind pressure differentials to move outdoor air through a building without fans.
Question 7: For BPI combustion safety testing, what is the maximum acceptable CO level measured in the undiluted flue gas of a gas appliance?
- 100 ppm
- 200 ppm
- 400 ppm (Correct answer)
- 800 ppm
Correct answer: 400 ppm
BPI standards set 400 ppm CO in undiluted flue gas as the action threshold — readings above this require the appliance to be shut down immediately.
BPI HVAC Systems 2
What does the ACCA Manual J calculation determine for a residential building?