Home Inspector Test Home Inspector Forced-Air Furnace Inspection 2 — Questions and Answers
Question 1: What is the minimum recommended clearance between a gas furnace and combustible materials in a typical residential installation?
- 1 inch
- 6 inches
- Varies by manufacturer — always check the nameplate (Correct answer)
- 18 inches
Correct answer: Varies by manufacturer — always check the nameplate
Clearance requirements vary by furnace model and must be verified on the manufacturer's nameplate or installation manual.
Question 2: A home inspector notices the furnace flue pipe has a downward slope toward the furnace. What is the concern?
- It reduces heating efficiency only
- Combustion gases may backdraft into the living space (Correct answer)
- The pipe will overheat and warp
- Condensation will damage the heat exchanger
Correct answer: Combustion gases may backdraft into the living space
Flue pipes must slope upward (minimum 1/4 inch per foot) toward the chimney so combustion gases draft properly and do not back-flow into the home.
Question 3: During a forced-air furnace inspection, the inspector observes soot deposits around the burner compartment. What does this most likely indicate?
- Normal combustion byproduct accumulation
- Improper combustion or a cracked heat exchanger (Correct answer)
- The filter has not been changed recently
- Excessive static pressure in the duct system
Correct answer: Improper combustion or a cracked heat exchanger
Soot accumulation around burners is a red flag for incomplete combustion or a cracked heat exchanger allowing combustion gases to escape.
Question 4: What is the purpose of the blower door on a furnace cabinet?
- To allow access for filter replacement only
- To prevent air from the blower compartment from mixing with combustion air and maintain proper airflow (Correct answer)
- To reduce noise from the blower motor
- To provide a secondary safety shutoff
Correct answer: To prevent air from the blower compartment from mixing with combustion air and maintain proper airflow
The blower door separates the blower compartment from the burner/heat exchanger and must be installed for safe and efficient operation.
Question 5: A furnace draft inducer motor is found on which type of furnace?
- Natural-draft atmospheric furnaces only
- Mid-efficiency or high-efficiency induced-draft furnaces (Correct answer)
- All furnaces regardless of AFUE rating
- Electric furnaces only
Correct answer: Mid-efficiency or high-efficiency induced-draft furnaces
Induced-draft furnaces use a draft inducer (vent blower) to mechanically pull combustion gases through the heat exchanger and out the flue.
Question 6: Which condition requires reporting as a safety defect when inspecting a gas furnace's gas supply line?
- Black iron pipe used for the main supply
- A flexible connector longer than 3 feet inside a confined space (Correct answer)
- Shutoff valve located within 6 feet of the furnace
- Sediment trap installed in the supply line
Correct answer: A flexible connector longer than 3 feet inside a confined space
Flexible gas connectors must not exceed the manufacturer's specified length (typically 3–6 feet) and should not pass through walls, floors, or ceilings.
Question 7: What does a cracked heat exchanger most directly risk in a forced-air system?
- Reduced airflow to upstairs rooms
- Carbon monoxide entering the living space via supply air (Correct answer)
- Increased gas consumption without heating benefit
- Premature blower motor failure
Correct answer: Carbon monoxide entering the living space via supply air
A crack allows combustion gases, including carbon monoxide, to mix with the circulating air and be distributed throughout the home.
Home Inspector Test Home Inspector Forced-Air Furnace Inspection 2
What is the minimum recommended clearance between a gas furnace and combustible materials in a typical residential installation?