HVAC NATE Exam Questions & Answers 2026 (1–10)

Question 1

What is the primary purpose of a supply duct in an HVAC system?

TheoryPractice · Accepted 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.

Question 2

Which unit is used to express airflow volume in HVAC ductwork?

TheoryPractice · Accepted 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.

Question 3

What does 'static pressure' represent in a duct system?

TheoryPractice · Accepted 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.

Question 4

Velocity pressure in a duct is best described as:

TheoryPractice · Accepted 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.

Question 5

Total pressure in a duct is the sum of which two pressures?

TheoryPractice · Accepted 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.

Question 6

The basic airflow equation CFM = Area × Velocity requires area in which unit?

TheoryPractice · Accepted 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.

Question 7

A 3-ton residential air conditioner requires 400 CFM per ton. What total airflow should the system deliver?

TheoryPractice · Accepted 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.

Question 8

Room-by-room CFM requirements are determined during which ACCA design procedure?

TheoryPractice · Accepted 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.

Question 9

A supply plenum feeds three branch ducts carrying 300, 450, and 250 CFM respectively. The main trunk must carry at least how much CFM?

TheoryPractice · Accepted 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.

Question 10

A 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?

TheoryPractice · Accepted 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.

HVAC NATE Exam Questions & Answers 2026 (1–10)

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