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
A home inspector tests a heat pump and finds it only provides heat via the electric resistance backup strips even in mild 50°F weather. What is the likely cause?
Answer: The reversing valve may be stuck or failed, preventing heat pump heating mode
If a heat pump defaults to auxiliary electric resistance heat in mild weather, the reversing valve (which switches between heating and cooling mode) is likely stuck in the cooling position.
What is the purpose of the secondary (auxiliary) condensate drain pan installed beneath an air handler in an attic?
Answer: To catch overflow if the primary drain pan or drain line becomes clogged, preventing ceiling damage
The secondary drain pan catches overflow from a clogged primary pan, preventing water from dripping onto the ceiling below; many installations include a safety float switch to shut down the system when water accumulates.
During inspection, an inspector notices the supply ductwork in an unconditioned crawl space is uninsulated. What is the primary problem this creates?
Answer: Conditioned air loses heat or gains heat through the duct walls, reducing system efficiency significantly
Uninsulated supply ducts in unconditioned spaces lose significant energy — heating ducts lose heat in winter and cooling ducts gain heat in summer — wasting energy and reducing comfort.
What is the correct method for a home inspector to test the operation of a gas furnace during a home inspection?
Answer: Set the thermostat above the current room temperature and observe that the system completes a full heating cycle
Home inspectors verify furnace operation by raising the thermostat set point above ambient temperature and observing that the furnace ignites, runs, and completes a heating cycle without tripping safety controls.
A home inspector observes a furnace installed in a bedroom closet with the return air grille drawing air directly from the closet. What is the safety concern?
Answer: If the furnace has a combustion air leak, combustion gases can be recirculated into the living area
When a combustion appliance shares return air space with living areas, any combustion gas spillage can be drawn into the air distribution system and delivered throughout the home.
Which of the following would indicate improper combustion air supply to a gas furnace installed in a confined space?
Answer: Flame rollout, soot deposits around the burner area, or repeated limit switch tripping
Flame rollout, soot staining around the burner compartment, and nuisance limit switch trips are classic signs of insufficient combustion air, causing incomplete and unstable combustion.
What is the purpose of the Emergency Shutoff switch (often a red switch near the top of basement stairs) required for heating systems?
Answer: To allow occupants or emergency responders to immediately shut down the heating system from outside the equipment room
The emergency shutoff switch (required by many codes near the entrance to the equipment room) allows rapid shutdown of the heating system without entering the equipment room during an emergency.