NHIE HVAC 3 — Questions and Answers
Question 1: What is the purpose of a barometric damper (draft regulator) found on an oil furnace flue?
- To increase combustion air supply to the burner
- To maintain consistent negative pressure (draft) in the flue regardless of wind conditions (Correct answer)
- To prevent rain from entering the chimney
- To reduce noise from the blower motor
Correct answer: To maintain consistent negative pressure (draft) in the flue regardless of wind conditions
A barometric damper automatically opens to admit room air into the flue when draft is too strong, maintaining a consistent negative pressure for safe combustion.
Question 2: During a home inspection, the inspector tests the cooling system and measures the temperature differential between the supply and return air. What is the acceptable range indicating normal operation?
- 5-10°F
- 14-22°F (Correct answer)
- 25-35°F
- 40-50°F
Correct answer: 14-22°F
A properly functioning air conditioning system should produce a 14-22°F temperature differential (delta T) between return and supply air under normal operating conditions.
Question 3: A home inspector observes refrigerant line sets running from the outdoor condenser to the air handler. Which line should feel cold/cool to the touch during normal air conditioning operation?
- The smaller diameter liquid line
- The larger diameter suction line (Correct answer)
- Both lines should feel the same temperature
- Neither line — both should be at ambient temperature
Correct answer: The larger diameter suction line
The larger suction line carries low-pressure refrigerant vapor returning to the compressor and should feel cool or cold, often with condensation forming on it.
Question 4: What is the minimum recommended distance between an air conditioning condenser unit and surrounding vegetation or structures to ensure proper airflow?
- 6 inches on all sides
- 12 inches on sides, 24 inches above
- 18-24 inches on sides, with unrestricted discharge above (Correct answer)
- 36 inches on all sides
Correct answer: 18-24 inches on sides, with unrestricted discharge above
Most manufacturers require 18-24 inches of clearance on the sides of a condenser and unrestricted space above to allow proper air discharge and prevent short-cycling of hot exhaust air.
Question 5: What component in a forced-air heating system is responsible for preventing the furnace from overheating?
- Pressure switch
- Limit switch (high-limit control) (Correct answer)
- Flame sensor
- Inducer motor
Correct answer: Limit switch (high-limit control)
The limit switch (high-limit control) monitors heat exchanger temperature and shuts off the burner if it exceeds a safe threshold, protecting the heat exchanger from thermal damage.
Question 6: A home inspector finds that a bathroom exhaust fan duct terminates in the attic rather than exiting the exterior. What is the primary concern?
- The fan will lose suction efficiency
- Moisture-laden air discharged into the attic can cause mold growth and wood rot (Correct answer)
- The attic insulation will filter the air sufficiently
- Code only requires exterior venting for kitchens, not bathrooms
Correct answer: Moisture-laden air discharged into the attic can cause mold growth and wood rot
Exhausting humid bathroom air into an attic introduces moisture that promotes mold growth, wood decay, and deterioration of insulation — a significant defect requiring correction.
Question 7: When inspecting a radiant floor heating system, which of the following would be reported as a defect?
- Boiler water temperature set at 130°F
- Expansion tank installed on supply side of boiler (Correct answer)
- Manifold with individual zone shutoffs
- Pressure relief valve discharging into a drain
Correct answer: Expansion tank installed on supply side of boiler
The expansion tank must be installed on the suction (return) side of the circulator pump, not the supply side, to function properly and prevent pressure problems.
NHIE HVAC 3
What is the purpose of a barometric damper (draft regulator) found on an oil furnace flue?