CHI Heating, Ventilation, & Air Conditioning (HVAC) Inspection 2 — Questions and Answers
Question 1: When inspecting a heat pump, which defrost cycle symptom indicates normal operation?
- Ice forming permanently on the outdoor coil
- Temporary steam rising from the outdoor unit during defrost (Correct answer)
- Refrigerant leaking from the service port
- The indoor fan shutting off permanently during defrost
Correct answer: Temporary steam rising from the outdoor unit during defrost
Steam rising from the outdoor unit is normal during a heat pump defrost cycle as the reversing valve briefly switches to cooling mode to melt accumulated ice.
Question 2: What is the minimum recommended clearance between a gas furnace flue vent and combustible materials?
- 1 inch (Correct answer)
- 6 inches
- 12 inches
- 18 inches
Correct answer: 1 inch
Single-wall metal flue pipe requires a minimum 6-inch clearance from combustibles, but high-efficiency furnaces with PVC venting require only 1 inch—however, B-vent requires 1 inch clearance per most codes.
Question 3: A home inspector notices the air handler's evaporator coil drain pan is full of standing water. What is the MOST likely cause?
- Oversized air conditioning unit
- Clogged condensate drain line (Correct answer)
- Refrigerant overcharge
- Dirty air filter
Correct answer: Clogged condensate drain line
A clogged condensate drain line prevents condensation from draining, causing the drain pan to overflow with standing water.
Question 4: Which HVAC component is responsible for reversing refrigerant flow in a heat pump to switch between heating and cooling modes?
- Expansion valve
- Compressor
- Reversing valve (Correct answer)
- Accumulator
Correct answer: Reversing valve
The reversing valve (four-way valve) changes the direction of refrigerant flow, allowing the heat pump to operate in both heating and cooling modes.
Question 5: During a home inspection, the inspector observes yellow or orange flames in a natural gas furnace burner. This indicates:
- Proper combustion with full fuel ignition
- Incomplete combustion possibly producing carbon monoxide (Correct answer)
- High-efficiency combustion above 95% AFUE
- Normal flame color for a gas appliance
Correct answer: Incomplete combustion possibly producing carbon monoxide
Yellow or orange flames in a gas burner indicate incomplete combustion, which can produce dangerous carbon monoxide; proper combustion produces a steady blue flame.
Question 6: What does AFUE stand for and what does it measure?
- Annual Fuel Utilization Efficiency — measures heating equipment efficiency over a season (Correct answer)
- Air Flow Unit Evaluation — measures duct airflow capacity
- Auxiliary Furnace Usage Estimate — measures backup heat usage
- Ambient Fuel Usage Equation — measures annual gas consumption
Correct answer: Annual Fuel Utilization Efficiency — measures heating equipment efficiency over a season
AFUE (Annual Fuel Utilization Efficiency) is a percentage representing how efficiently a furnace or boiler converts fuel to heat over an entire heating season.
Question 7: A home inspector finds that the return air duct is located in the same mechanical room as a gas furnace. What is the primary safety concern?
- Reduced airflow efficiency due to short cycling
- Backdrafting of combustion gases into the living space (Correct answer)
- Excessive noise transmission through the duct
- Condensation forming on the duct exterior
Correct answer: Backdrafting of combustion gases into the living space
Return air ducts in the same space as combustion appliances can draw combustion gases—including carbon monoxide—into the air distribution system and circulate them throughout the home.
CHI Heating, Ventilation, & Air Conditioning (HVAC) Inspection 2
When inspecting a heat pump, which defrost cycle symptom indicates normal operation?