BPI HVAC Systems 3 — Questions and Answers
Question 1: What is the function of the metering device in a refrigeration cycle?
- Remove superheat from refrigerant vapor
- Reduce refrigerant pressure and temperature entering the evaporator (Correct answer)
- Compress low-pressure refrigerant vapor
- Transfer heat from indoor air to refrigerant
Correct answer: Reduce refrigerant pressure and temperature entering the evaporator
The metering device (such as a TXV or orifice) drops refrigerant pressure and temperature so it can absorb heat effectively in the evaporator.
Question 2: A BPI analyst measures a 0.5 inches of water column (IWC) depressurization of the combustion appliance zone (CAZ) with all exhaust fans on. What action is required?
- No action; this reading is within acceptable limits
- Retest with windows open
- Flag as a spillage concern and investigate further (Correct answer)
- Immediately red-tag all appliances
Correct answer: Flag as a spillage concern and investigate further
A CAZ depressurization of -0.5 IWC indicates potentially unsafe backdrafting conditions that require further investigation before completing weatherization work.
Question 3: Which duct insulation R-value is typically required by energy codes for ducts located in unconditioned attics in climate zones 4 and above?
- R-4
- R-6
- R-8 (Correct answer)
- R-10
Correct answer: R-8
Energy codes generally require R-8 duct insulation for supply and return ducts located in unconditioned attics in higher climate zones.
Question 4: What does HSPF measure for a heat pump?
- Cooling efficiency over a cooling season
- Heating efficiency over a heating season (Correct answer)
- Instantaneous heating coefficient of performance
- Fan motor efficiency at rated airflow
Correct answer: Heating efficiency over a heating season
Heating Seasonal Performance Factor (HSPF) represents the total heating output divided by total energy consumed over an entire heating season.
Question 5: In a split-system air conditioner, where does heat rejection to the outdoors occur?
- Evaporator coil
- Compressor housing
- Condenser coil (Correct answer)
- Metering device
Correct answer: Condenser coil
The condenser coil, located in the outdoor unit, releases the heat absorbed indoors plus the heat of compression to the outside air.
Question 6: What is the recommended minimum refrigerant superheat leaving the evaporator coil for a fixed-orifice system?
- 0–5°F
- 5–10°F
- 10–18°F (Correct answer)
- 20–30°F
Correct answer: 10–18°F
A superheat of 10–18°F at the evaporator outlet ensures no liquid refrigerant enters the compressor while confirming the coil is being fully utilized.
Question 7: Which type of heat exchanger failure in a gas furnace presents the greatest immediate safety hazard to occupants?
- Cracked heat exchanger allowing combustion gases into supply air (Correct answer)
- Corroded secondary heat exchanger fins
- Failed draft inducer motor bearing
- Blocked condensate drain in a high-efficiency unit
Correct answer: Cracked heat exchanger allowing combustion gases into supply air
A cracked primary heat exchanger can allow carbon monoxide and other combustion byproducts to mix with conditioned supply air delivered to living spaces.
BPI HVAC Systems 3
What is the function of the metering device in a refrigeration cycle?