HVAC Flashcards
7 cards from real NHIE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 HVAC flashcards as text
What is the purpose of a barometric damper (draft regulator) found on an oil furnace flue?
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.
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?
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.
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?
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.
What is the minimum recommended distance between an air conditioning condenser unit and surrounding vegetation or structures to ensure proper airflow?
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.
What component in a forced-air heating system is responsible for preventing the furnace from overheating?
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.
A home inspector finds that a bathroom exhaust fan duct terminates in the attic rather than exiting the exterior. What is the primary concern?
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.
When inspecting a radiant floor heating system, which of the following would be reported as a defect?
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.