TheoryFree HVAC NATE Practice Test
Take a free HVAC NATE practice test for 2026 with questions, answers, explanations, PDF download and timed mock exam links.
HVAC NATE Questions
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Q1What is the primary purpose of a supply duct in an HVAC system?
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✓ Correct answer: Deliver conditioned air from the air handler to the occupied space
Supply ducts carry conditioned (heated or cooled) air from the air-handling unit to registers in the occupied space. Return ducts perform the reverse function, pulling room air back to be reconditioned.
Q2Which unit is used to express airflow volume in HVAC ductwork?
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✓ Correct answer: Cubic feet per minute (CFM)
Airflow volume is measured in cubic feet per minute (CFM). FPM measures velocity, and in. w.c. measures static pressure — both related but distinct from volume.
Q3What does 'static pressure' represent in a duct system?
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✓ Correct answer: The pressure exerted equally in all directions on the duct walls
Static pressure acts outward in all directions on duct walls and is what drives leakage through seams and holes. It is distinct from velocity pressure, which acts only in the direction of airflow.
Q4Velocity pressure in a duct is best described as:
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✓ Correct answer: The pressure component due to the kinetic energy of moving air
Velocity pressure (VP) results from the kinetic energy of air in motion. It acts only in the direction of airflow and equals (V/4005)² in. w.c., where V is velocity in FPM at standard air density.
Q5Total pressure in a duct is the sum of which two pressures?
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✓ Correct answer: Static pressure and velocity pressure
Total pressure = static pressure + velocity pressure (Bernoulli). Knowing total pressure is essential for understanding how fans and ducts interact at any operating point.
Q6The basic airflow equation CFM = Area × Velocity requires area in which unit?
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✓ Correct answer: Square feet
When velocity is in feet per minute (FPM), area must be in square feet to produce CFM directly. Convert square inches to square feet by dividing by 144.
Q7A 3-ton residential air conditioner requires 400 CFM per ton. What total airflow should the system deliver?
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✓ Correct answer: 1,200 CFM
400 CFM/ton × 3 tons = 1,200 CFM. The 400 CFM/ton rule of thumb is a standard residential design target ensuring adequate sensible heat removal and coil performance.
Q8Room-by-room CFM requirements are determined during which ACCA design procedure?
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✓ Correct answer: Manual J (residential load calculation)
ACCA Manual J calculates room-by-room heating and cooling loads, which are converted to CFM requirements. Manual D uses those CFM values to size ducts; Manual S selects the equipment.
Q9A supply plenum feeds three branch ducts carrying 300, 450, and 250 CFM respectively. The main trunk must carry at least how much CFM?
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✓ Correct answer: 1,000 CFM
The main trunk must carry the sum of all branches: 300 + 450 + 250 = 1,000 CFM. Conservation of mass (continuity equation) requires airflow entering a junction to equal airflow leaving.
Q10A space has a sensible cooling load of 10,800 BTU/h with a supply-air temperature of 55°F and a room design temperature of 75°F. What supply airflow is required?
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✓ Correct answer: 500 CFM
CFM = Q ÷ (1.08 × ΔT) = 10,800 ÷ (1.08 × 20) = 10,800 ÷ 21.6 = 500 CFM. The constant 1.08 = 0.075 lb/ft³ × 0.24 BTU/(lb·°F) × 60 min/hr, applicable at standard air density.
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