InterNACHI HVAC Systems Analysis 2 — Questions and Answers
Question 1: What is the typical minimum clearance required between a gas furnace and combustible materials?
- 1 inch
- 6 inches
- 12 inches
- Per manufacturer specifications (Correct answer)
Correct answer: Per manufacturer specifications
Clearance requirements vary by furnace model and must follow the manufacturer's installation instructions, which take precedence over generic rules.
Question 2: Which condition indicates a cracked heat exchanger in a gas furnace?
- Yellow or orange burner flame (Correct answer)
- Soot accumulation on burner ports
- Visible rust on the exterior cabinet
- High static pressure readings
Correct answer: Yellow or orange burner flame
A cracked heat exchanger allows combustion gases to mix with supply air, causing the burner flame to roll out or appear yellow/orange due to disrupted airflow.
Question 3: What does SEER stand for in relation to air conditioning equipment?
- Seasonal Energy Efficiency Ratio (Correct answer)
- Standard Energy Evaluation Rating
- System Efficiency and Energy Report
- Seasonal Equipment Efficiency Review
Correct answer: Seasonal Energy Efficiency Ratio
SEER (Seasonal Energy Efficiency Ratio) measures cooling output divided by electrical energy input over a typical cooling season.
Question 4: A home inspector notices the condensate drain line on an air handler is dripping water at the connection joint. What should be reported?
- Normal condensation, no action needed
- Improper drain line installation or joint failure requiring repair (Correct answer)
- The unit is low on refrigerant
- The evaporator coil is frozen
Correct answer: Improper drain line installation or joint failure requiring repair
A leaking condensate drain joint indicates a failed or improperly installed connection that can cause water damage and should be repaired by a qualified technician.
Question 5: Which component in a heat pump system reverses the refrigerant flow to switch between heating and cooling modes?
- Expansion valve
- Reversing valve (four-way valve) (Correct answer)
- Compressor
- Accumulator
Correct answer: Reversing valve (four-way valve)
The reversing valve (four-way valve) redirects refrigerant flow so the heat pump can absorb heat from outside in winter or reject heat outside in summer.
Question 6: What is the recommended maximum temperature rise across a gas furnace heat exchanger?
- 10–20°F
- 25–35°F
- 35–70°F (Correct answer)
- 80–100°F
Correct answer: 35–70°F
Most gas furnaces are designed for a temperature rise of 35–70°F across the heat exchanger; values outside this range indicate airflow or equipment issues.
Question 7: During an inspection, you observe rust staining and moisture around the base of a furnace flue pipe. What is the most likely cause?
- Normal condensation in high-efficiency furnaces
- Flue gas backdrafting or improper venting (Correct answer)
- Refrigerant leak from the evaporator coil
- Dirty air filter restricting airflow
Correct answer: Flue gas backdrafting or improper venting
Rust and moisture at a conventional furnace flue indicate that combustion gases are condensing inside the vent, typically due to backdrafting or undersized flue pipe.
InterNACHI HVAC Systems Analysis 2
What is the typical minimum clearance required between a gas furnace and combustible materials?