Home Inspector Test Home Inspector Forced-Air Furnace Inspection 4 — Questions and Answers
Question 1: A furnace located in a bedroom closet requires combustion air. What is the most common compliant solution for this confined space?
- Installing a larger return air grille in the closet door
- Providing two openings connecting to the outdoors or to adjacent spaces with adequate volume
- Using a sealed-combustion (direct-vent) appliance that draws combustion air from outside (Correct answer)
- Leaving the closet door open during furnace operation
Correct answer: Using a sealed-combustion (direct-vent) appliance that draws combustion air from outside
A sealed-combustion furnace draws all combustion air directly from outdoors through a dedicated pipe, making it ideal for confined installations.
Question 2: What is the purpose of a condensate neutralizer on a high-efficiency furnace?
- To remove mineral deposits from the heat exchanger
- To raise the pH of acidic condensate before it enters the drain system (Correct answer)
- To prevent condensate from freezing in cold climates
- To measure condensate volume for efficiency calculations
Correct answer: To raise the pH of acidic condensate before it enters the drain system
Condensing furnace condensate is mildly acidic (pH 2.9–6.5) and can corrode drain lines; a neutralizer raises pH to acceptable levels before disposal.
Question 3: During inspection, the inspector notices the furnace burners produce a lazy yellow or orange flame rather than a sharp blue flame. What does this indicate?
- The furnace is operating at peak efficiency
- Incomplete combustion due to improper air-fuel mixture, possibly indicating a dirty burner or restricted air supply (Correct answer)
- The thermostat is set too high
- The heat exchanger is oversized
Correct answer: Incomplete combustion due to improper air-fuel mixture, possibly indicating a dirty burner or restricted air supply
A properly adjusted gas burner burns with a blue flame; yellow or orange flames indicate incomplete combustion, which can produce carbon monoxide.
Question 4: Which of the following is the correct test method a home inspector uses to check for a cracked heat exchanger?
- Applying soapy water to the heat exchanger seams and looking for bubbles
- Observing flame behavior when the blower activates, listening for odors, and using a combustion gas analyzer (Correct answer)
- Removing and visually inspecting every panel of the heat exchanger
- Measuring supply air CO2 levels with a meter
Correct answer: Observing flame behavior when the blower activates, listening for odors, and using a combustion gas analyzer
Home inspectors check for heat exchanger cracks by observing flame deflection when the blower starts, noting odors at registers, and using a combustion gas detector — not by disassembly.
Question 5: A gas furnace is installed in a garage. Which additional safety requirement applies to this installation?
- The furnace must be rated for outdoor use
- The furnace burner and ignition sources must be elevated at least 18 inches above the floor (Correct answer)
- A carbon monoxide detector must be hardwired directly to the furnace control board
- The gas line must be stainless steel in a garage environment
Correct answer: The furnace burner and ignition sources must be elevated at least 18 inches above the floor
In garages, furnaces must be elevated 18 inches above the floor to keep ignition sources above the level where gasoline vapors (which are heavier than air) can accumulate.
Question 6: What does the term 'AFUE' stand for, and what does it measure?
- Annual Fuel Usage Estimate — the yearly cost of operating the furnace
- Annual Fuel Utilization Efficiency — the percentage of fuel energy converted to heat (Correct answer)
- Airflow Filtration and Duct Unit Efficiency — duct system leakage rating
- Approved Furnace Utility Emissions — EPA carbon output standard
Correct answer: Annual Fuel Utilization Efficiency — the percentage of fuel energy converted to heat
AFUE measures what percentage of fuel energy the furnace converts to usable heat over an entire heating season; a 95 AFUE furnace wastes only 5% of fuel.
Question 7: An inspector finds the furnace vent connector passing through a combustible interior wall without a proper thimble or listed pass-through device. This is reported as:
- A maintenance item requiring monitoring
- A safety defect requiring correction before occupancy (Correct answer)
- Acceptable if the pipe has been in place more than 10 years
- An informational note if the clearance appears adequate visually
Correct answer: A safety defect requiring correction before occupancy
Vent connectors passing through combustible walls require a listed thimble or pass-through device to maintain required clearances and prevent fire risk.
Home Inspector Test Home Inspector Forced-Air Furnace Inspection 4
A furnace located in a bedroom closet requires combustion air.
What is the most common compliant solution for this confined space?