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Question 1. Which of the following best defines the term “specific heat”? A) The amount of heat required to raise the temperature of 1 kg of a substance by 1 °C B) The heat energy released when a substance changes phase C) The temperature at which a substance begins to vaporize D) The pressure change associated with a temperature increase Answer: A Explanation: Specific heat is the quantity of heat needed to raise the temperature of 1 kg of a material by 1 °C (or 1 K). Question 2. Converting 68 °F to Celsius yields: A) 15 °C B) 20 °C C) 25 °C D) 30 °C Answer: B Explanation: °C = (°F – 32) × 5/9 → (68‑32) × 5/9 = 20 °C. Question 3. The Zeroth Law of Thermodynamics states that: A) Energy cannot be created or destroyed. B) Heat flows from hot to cold spontaneously. C) If two systems are each in thermal equilibrium with a third, they are in equilibrium with each other. D) Entropy of an isolated system always increases.
Answer: C Explanation: The Zeroth Law defines thermal equilibrium and enables temperature measurement. Question 4. In HVAC, latent heat is primarily associated with: A) Raising the temperature of air. B) Changing the moisture content of air without a temperature change. C) Heat loss through walls. D) Heat generated by electrical components. Answer: B Explanation: Latent heat is the energy required for phase change of water vapor, affecting humidity without altering dry‑bulb temperature. Question 5. Which mode of heat transfer does a radiant floor system primarily use? A) Conduction only B) Convection only C) Radiation only D) Both convection and radiation Answer: D Explanation: Radiant floors heat the floor surface (radiation) and the warmed air circulates (convection). Question 6. On a psychrometric chart, moving vertically upward at constant humidity ratio represents: A) Sensible heating B) Sensible cooling
Question 9. To calculate heat loss through a wall, which formula is correct? A) Q = U × A × ΔT B) Q = R × A ÷ ΔT C) Q = U ÷ A × ΔT D) Q = R × ΔT ÷ A Answer: A Explanation: Heat loss Q (BTU/h) = U‑value × area × temperature difference. Question 10. A building has an infiltration air change rate of 0.5 ACH. Which unit best expresses this rate? A) Cubic feet per minute (CFM) B) Liters per second (L/s) C) Air changes per hour (ACH) D) Pounds per square foot (psf) Answer: C Explanation: ACH directly denotes the number of times the building’s air volume is replaced per hour. Question 11. In duct design, total pressure is the sum of: A) Static pressure and velocity pressure B) Static pressure only C) Velocity pressure only D) Friction loss and leakage loss
Answer: A Explanation: Total pressure = static pressure + velocity pressure; it drives airflow through ducts. Question 12. Oversizing a furnace can lead to which of the following problems? A) Increased fuel consumption B) Short‑cycling and reduced comfort C) Lower combustion efficiency D) All of the above Answer: D Explanation: An oversized furnace cycles quickly (short‑cycling), wastes fuel, and operates at lower efficiency. Question 13. Which fuel type typically provides the highest AFUE rating for residential furnaces? A) Natural gas B) Propane C) Oil D) Electric resistance Answer: A Explanation: Modern high‑efficiency natural‑gas furnaces can achieve AFUE > 97 %; electric resistance has 100 % but is not a “furnace” in the traditional sense. Question 14. The primary purpose of a furnace’s blower motor’s run capacitor is to: A) Provide starting torque
Explanation: LWCO detects low water levels in hot‑water boilers and shuts down the burner to avoid overheating. Question 17. A hydronic radiator that is “air bound” will most likely exhibit: A) Cold spots at the top of the radiator B) Uniform heating across the entire unit C) Excessive noise and hammering D) Rapid temperature rise Answer: A Explanation: Air trapped at the top prevents water from filling the upper sections, causing cold spots. Question 18. In a steam heating system, the purpose of a “vent” on a radiator is to: A) Release condensate water back to the boiler B) Allow air to escape during start‑up, preventing water hammer C) Regulate steam pressure locally D) Provide a secondary heat source Answer: B Explanation: Air venting lets trapped air escape, ensuring steam fills the radiator and preventing water hammer. Question 19. The reversing valve in a heat pump is responsible for: A) Switching the direction of refrigerant flow between heating and cooling modes B) Controlling the compressor speed C) Defrosting the outdoor coil
D) Regulating indoor air humidity Answer: A Explanation: The reversing valve changes the refrigerant flow path, enabling the system to heat or cool. Question 20. During a heat pump’s defrost cycle, which component typically operates to protect the indoor coil? A) Outdoor fan shuts off B) Indoor fan continues running C) Compressor stops completely D) Reversing valve stays in heating position Answer: B Explanation: The indoor fan often continues to circulate warm air while the outdoor coil is defrosted, maintaining indoor comfort. Question 21. Which of the following water heater types typically requires a vent for combustion gases? A) Electric storage tank B) Propane tank‑type water heater C) Gas‑less tankless water heater D) Solar‑only water heater Answer: B Explanation: Propane tank‑type water heaters burn fuel and must vent exhaust gases.
Answer: B Explanation: PSC motors are efficient, low‑cost, and commonly power furnace blowers. Question 25. A low‑voltage thermostat typically operates at which voltage? A) 120 V AC B) 240 V AC C) 24 V AC D) 12 V DC Answer: C Explanation: Residential thermostats are usually powered by a 24 V AC transformer. Question 26. A high‑limit safety control in a furnace is designed to: A) Detect flame loss B) Shut down the burner if water temperature exceeds a set point C) Monitor indoor thermostat signal D) Control blower speed Answer: B Explanation: The high‑limit switch prevents overheating by cutting off the burner when water temperature is too high. Question 27. When using a multimeter to measure AC voltage across a furnace’s transformer secondary, which setting should be selected? A) DC voltage B) AC voltage (≥ 250 V range)
C) Resistance (Ω) D) Continuity Answer: B Explanation: The secondary provides AC voltage; the appropriate AC voltage range must be selected. Question 28. In a combustion analysis, a measured flue gas O₂ level of 5 % indicates: A) Too rich a mixture (excess fuel) B) Too lean a mixture (excess air) C) Perfect combustion D) Presence of carbon monoxide Answer: B Explanation: High O₂ in flue gases means excess combustion air, indicating a lean mixture. Question 29. Which tool is best suited for measuring the pressure drop across a furnace heat exchanger? A) Clamp‑on ammeter B) Manometer C) Thermocouple D) Hygrometer Answer: B Explanation: A manometer measures static pressure differences, useful for pressure drop checks.
Answer: B Explanation: Zone valves allow independent on/off control of different heating zones. Question 33. A locked‑out gas valve must be reset after which of the following actions? A) Replacing a thermostat battery B) Clearing a flame sensor obstruction C) Adjusting ductwork D) Changing a blower motor Answer: B Explanation: If the flame sensor is cleared and the gas valve was locked out due to a flame‑out, it must be manually reset. Question 34. The purpose of a “combustion air intake” in a direct‑vent furnace is to: A) Supply fresh air for combustion from outside, preventing indoor air depletion B) Provide secondary heating for the living space C) Reduce the furnace’s noise level D) Increase the furnace’s efficiency by pre‑heating the intake air Answer: A Explanation: Direct‑vent units draw combustion air directly from the outdoors, isolating the indoor environment. Question 35. Which of the following refrigerants is classified as a low‑GWP (global warming potential) option for heat pumps? A) R‑ 22
B) R‑410A
C) R‑290 (propane) D) R‑134a Answer: C Explanation: R‑290 (propane) has a low GWP and is used in many modern heat‑pump systems. Question 36. According to ASHRAE 62.2, the minimum required ventilation rate for a residential dwelling is: A) 0.35 CFM per square foot of floor area B) 0.5 ACH C) 15 CFM per person D) 30 CFM per bedroom Answer: A Explanation: ASHRAE 62.2 specifies 0.35 CFM per ft² of conditioned floor area as the baseline ventilation rate. Question 37. The “lockout/tagout” (LOTO) procedure primarily protects workers from: A) Chemical exposure B) Electrical shock and unexpected startup of equipment C) Noise-induced hearing loss D) Ergonomic injuries Answer: B
B) A fan that pushes combustion air into the furnace C) Natural buoyancy of hot gases without a fan D) A pressure differential created by a heat exchanger Answer: A Explanation: Induced‑draft fans create a negative pressure to draw exhaust gases out of the appliance. Question 41. Which of the following is a typical symptom of a dirty indoor coil on a heat pump? A) Reduced heating capacity and longer run times B. Excessive noise during operation C. High outdoor air temperature readings D. Frequent defrost cycles Answer: A Explanation: A dirty coil impedes heat transfer, lowering capacity and causing longer run times. Question 42. In a water‑source heat pump, the heat exchange occurs primarily between: A) The refrigerant and outdoor air B) The refrigerant and a water loop (ground‑source or cooling tower) C) The refrigerant and indoor air D) The refrigerant and combustion gases Answer: B Explanation: Water‑source heat pumps use a water loop as the heat‑transfer medium.
Question 43. The “Btu/h per ton” rating for air‑conditioning equipment is: A) 12,000 Btu/h per ton B) 3,000 Btu/h per ton C) 6,000 Btu/h per ton D) 9,000 Btu/h per ton Answer: A Explanation: One ton of cooling equals 12,000 Btu/h. Question 44. Which type of thermostat wiring uses two separate 120 V hot wires? A) Low‑voltage (24 V) thermostat B) Line‑voltage (120 V) thermostat C) Line‑voltage (240 V) thermostat D) Smart Wi‑Fi thermostat Answer: B Explanation: Line‑voltage thermostats directly switch 120 V circuits, using two hot wires. Question 45. During a combustion analysis, a measured CO₂ level of 12 % suggests: A) Very lean combustion B) Very rich combustion C) Efficient combustion with proper air‑fuel ratio D) Presence of incomplete combustion Answer: C
D. Filtering dust particles Answer: B Explanation: The primary heat exchanger transfers combustion heat to the circulating air. Question 49. The term “enthalpy” in psychrometrics refers to: A. The total heat content of moist air per unit mass B. The moisture content of air expressed in grains per pound C. The temperature at which air becomes saturated D. The pressure difference across a damper Answer: A Explanation: Enthalpy (Btu/lb) combines sensible and latent heat of moist air. Question 50. A “direct‑vent” furnace differs from a “natural‑vent” furnace in that it: A. Uses a fan to push exhaust gases out a chimney B. Draws combustion air and exhaust through the same sealed pipe C. Requires no venting at all D. Operates only on electricity Answer: B Explanation: Direct‑vent units have a sealed pipe that supplies combustion air and exhausts gases, isolating indoor air. Question 51. Which of the following is the most common cause of a “no‑heat” condition in an electric furnace?
A. Faulty gas valve B. Tripped high‑limit switch C. Open circuit in the heating element D. Clogged burner nozzle Answer: C Explanation: Electric furnaces rely on heating elements; an open circuit prevents heat generation. Question 52. In a boiler, the “blow‑down” valve is used to: A. Remove excess water from the system B. Reduce dissolved solids concentration by flushing water out C. Increase system pressure during start‑up D. Control the temperature of the circulating water Answer: B Explanation: Blow‑down removes a portion of water containing high mineral content, maintaining water quality. Question 53. The “sensible heat ratio” (SHR) for a cooling coil is defined as: A. Sensible cooling ÷ total cooling B. Latent cooling ÷ total cooling C. Total cooling ÷ sensible cooling D. Sensible cooling ÷ latent cooling Answer: A
