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- What is the primary purpose of a refrigerant in an HVAC system? A) Increase humidity B) Transfer heat C) Generate electricity D) Filter air Correct Answer: B) Transfer heat Rationale: Refrigerant is the working fluid in HVAC systems designed to absorb heat from one area and release it in another through phase changes (evaporation and condensation), enabling cooling and heating cycles.
- Which component starts the refrigeration cycle? A) Evaporator B) Compressor C) Expansion valve D) Condenser Correct Answer: B) Compressor Rationale: The compressor pressurizes low-pressure refrigerant vapor,
raising its temperature and energy level so it can move through the system and release heat in the condenser.
- What happens to refrigerant in the evaporator? A) It condenses into liquid B) It absorbs heat and evaporates C) It is compressed D) It is filtered Correct Answer: B) Absorbs heat and evaporates Rationale: In the evaporator, low-pressure refrigerant absorbs heat from indoor air and changes from liquid to vapor, producing cooling effect.
- What tool is used to measure system pressure? A) Thermometer B) Manometer C) Psychrometer D) Clamp meter Correct Answer: B) Manometer Rationale: A manometer or manifold gauge set measures refrigerant pressure in both high and low sides of the HVAC system for diagnostics and charging.
- Which refrigerant state has the highest pressure? A) Low-pressure vapor B) Low-pressure liquid C) High-pressure vapor D) Saturated mist Correct Answer: C) High-pressure vapor Rationale: After compression, refrigerant becomes high-pressure, high- temperature vapor, which is essential for heat rejection in the condenser.
- What does superheat measure? A) Liquid refrigerant temperature B) Air temperature only C) Vapor temperature above boiling point D) Condenser temperature Correct Answer: C) Vapor temperature above boiling point Rationale: Superheat ensures all liquid refrigerant has evaporated before reaching the compressor, preventing liquid slugging damage. 10.What is subcooling? A) Cooling air below freezing B) Cooling refrigerant below condensation temperature C) Heating refrigerant D) Compressing vapor Correct Answer: B) Cooling refrigerant below condensation temperature Rationale: Subcooling ensures liquid refrigerant leaving the condenser is fully condensed and increases system efficiency. 11.What is the purpose of HVAC filters? A) Increase airflow resistance B) Remove airborne particles C) Increase humidity D) Cool refrigerant Correct Answer: B) Remove airborne particles Rationale: Filters trap dust, debris, and contaminants, protecting system components and improving indoor air quality. 12.What is the main function of a thermostat? A) Control refrigerant flow B) Measure humidity
C) Control system temperature operation D) Compress air Correct Answer: C) Control system temperature operation Rationale: A thermostat senses room temperature and signals HVAC equipment to turn on or off to maintain desired conditions. 13.What type of motor is commonly used in HVAC blowers? A) Stepper motor B) Induction motor C) Servo motor D) Hydraulic motor Correct Answer: B) Induction motor Rationale: Induction motors are durable, efficient, and widely used in HVAC fans and blowers due to their reliability and low maintenance. 14.What is airflow measured in HVAC systems? A) PSI B) BTU C) CFM D) KW Correct Answer: C) CFM Rationale: Cubic feet per minute (CFM) measures the volume of air moving through a system, critical for proper heating and cooling performance. 15.What does BTU stand for? A) British Thermal Unit B) Basic Thermal Utility C) Balanced Transfer Unit D) Boiler Temperature Unit
19.What is the function of a capacitor in HVAC motors? A) Store refrigerant B) Start and run motor efficiently C) Increase airflow D) Reduce voltage permanently Correct Answer: B) Start and run motor efficiently Rationale: Capacitors provide an electrical boost needed to start motors and maintain efficient operation during running conditions. 20.What does a psychrometer measure? A) Refrigerant pressure B) Air velocity C) Humidity D) Voltage Correct Answer: C) Humidity Rationale: A psychrometer measures relative humidity using dry-bulb and wet-bulb temperature readings. 21.What is the role of ductwork in HVAC systems? A) Store refrigerant B) Distribute conditioned air C) Compress air D) Generate heat Correct Answer: B) Distribute conditioned air Rationale: Ductwork delivers heated or cooled air throughout a building and returns air back to the system. 22.What is static pressure in HVAC systems? A) Refrigerant weight
B) Resistance to airflow C) Air temperature D) Compressor speed Correct Answer: B) Resistance to airflow Rationale: Static pressure measures resistance within duct systems and impacts airflow efficiency and equipment performance. 23.What does a TXV regulate? A) Voltage B) Airflow C) Refrigerant flow D) Humidity Correct Answer: C) Refrigerant flow Rationale: The thermostatic expansion valve regulates refrigerant entering the evaporator based on cooling demand. 24.What is the purpose of a condenser fan? A) Increase refrigerant pressure B) Remove heat from condenser coil C) Heat indoor air D) Compress vapor Correct Answer: B) Remove heat from condenser coil Rationale: The fan moves air across the condenser coil to dissipate heat absorbed from the indoor environment. 25.What is refrigerant leak detection commonly done with? A) Infrared camera B) Hammer C) Multimeter D) Clamp meter
29.What is the most common HVAC refrigerant today? A) R- 22 B) R-410A C) Ammonia D) Water vapor Correct Answer: B) R-410A Rationale: R-410A is widely used due to higher efficiency and compliance with environmental regulations. 30.What is the purpose of a defrost cycle in heat pumps? A) Increase cooling B) Remove ice buildup on outdoor coil C) Increase humidity D) Reduce voltage Correct Answer: B) Remove ice buildup on outdoor coil Rationale: Defrost cycles temporarily reverse operation or use heat to melt ice, maintaining efficiency in cold conditions. 31.What does a voltmeter measure? A) Current B) Resistance C) Voltage D) Pressure Correct Answer: C) Voltage Rationale: A voltmeter measures electrical potential difference, critical for diagnosing HVAC electrical issues. 32.What is the purpose of a relay? A) Measure airflow
B) Control high-voltage circuit using low voltage C) Cool refrigerant D) Increase humidity Correct Answer: B) Control high-voltage circuit using low voltage Rationale: Relays allow small control signals to operate larger electrical loads safely. 33.What is a common symptom of low refrigerant charge? A) High cooling performance B) Reduced cooling capacity C) Increased humidity removal D) Higher airflow Correct Answer: B) Reduced cooling capacity Rationale: Low refrigerant reduces heat absorption in the evaporator, lowering system performance. 34.What is the purpose of a sight glass? A) Measure airflow B) Observe refrigerant condition C) Control voltage D) Increase pressure Correct Answer: B) Observe refrigerant condition Rationale: A sight glass helps technicians check refrigerant flow, moisture presence, and charge level. 35.What does a compressor clutch do in HVAC systems? A) Regulates air B) Engages compressor operation C) Measures humidity D) Filters refrigerant
39.What is airflow imbalance caused by? A) Equal duct size B) Blocked or undersized ducts C) High refrigerant charge D) Clean filters Correct Answer: B) Blocked or undersized ducts Rationale: Restrictions in duct systems cause uneven distribution of conditioned air. 40.What is the purpose of an economizer in HVAC systems? A) Increase refrigerant pressure B) Use outside air for cooling when possible C) Heat air D) Compress air Correct Answer: B) Use outside air for cooling when possible Rationale: Economizers reduce energy consumption by using cool outdoor air instead of mechanical cooling. 41.What does a thermal overload protector do? A) Increases voltage B) Protects motor from overheating C) Measures humidity D) Controls airflow Correct Answer: B) Protects motor from overheating Rationale: It shuts down electrical components when excessive heat is detected to prevent damage. 42.What is the main function of a furnace? A) Cool air
B) Heat air C) Filter refrigerant D) Compress air Correct Answer: B) Heat air Rationale: Furnaces generate heat using gas, electricity, or oil to warm indoor air. 43.What is combustion efficiency? A) Airflow rate B) Heat output vs fuel input C) Refrigerant ratio D) Voltage output Correct Answer: B) Heat output vs fuel input Rationale: Combustion efficiency measures how effectively fuel is converted into usable heat. 44.What is a common refrigerant pressure measurement unit? A) Fahrenheit B) PSI C) BTU D) RPM Correct Answer: B) PSI Rationale: Pounds per square inch (PSI) measures refrigerant pressure in HVAC systems. 45.What is the purpose of a condensate drain? A) Supply refrigerant B) Remove moisture from system C) Increase pressure D) Heat air
49.What is the purpose of a duct damper? A) Increase refrigerant flow B) Control airflow distribution C) Compress air D) Measure voltage Correct Answer: B) Control airflow distribution Rationale: Dampers regulate airflow to different zones in HVAC systems. 50.What is the main cause of poor indoor air quality? A) Clean filters B) Lack of ventilation C) High voltage D) Proper insulation Correct Answer: B) Lack of ventilation Rationale: Insufficient fresh air exchange leads to buildup of contaminants, humidity, and pollutants indoors. CONTINUATION (51–100) 51.What is the purpose of a crankcase heater? A) Cool refrigerant B) Prevent refrigerant migration into compressor oil C) Increase airflow D) Measure humidity Correct Answer: B) Prevent refrigerant migration into compressor oil Rationale: It keeps compressor oil warm during shutdown to prevent refrigerant from mixing with oil, which could cause foaming and damage on startup.
52.What is the effect of dirty condenser coils? A) Increased efficiency B) Reduced heat rejection C) Lower pressure always D) Higher airflow Correct Answer: B) Reduced heat rejection Rationale: Dirt buildup restricts heat transfer, causing higher system pressures and reduced efficiency. 53.What is a common sign of a failing capacitor? A) Strong cooling B) Motor not starting C) Increased airflow D) Low refrigerant Correct Answer: B) Motor not starting Rationale: A weak or failed capacitor cannot provide the necessary starting torque for motors. 54.What is a PID controller used for? A) Refrigerant storage B) Precise temperature control C) Air filtration D) Voltage increase Correct Answer: B) Precise temperature control Rationale: PID controllers continuously adjust system output to maintain stable temperature conditions. 55.What does duct velocity refer to? A) Pressure level B) Speed of air movement
Rationale: Air and other gases increase pressure and reduce heat transfer efficiency. 59.What is a common refrigerant leak location? A) Duct insulation B) Evaporator coil joints C) Air filter D) Thermostat Correct Answer: B) Evaporator coil joints Rationale: Joints and connections are high-risk areas due to vibration and thermal expansion. 60.What is the purpose of a flame sensor? A) Measure airflow B) Detect burner flame presence C) Control refrigerant D) Increase humidity Correct Answer: B) Detect burner flame presence Rationale: It ensures safe combustion by shutting off gas if no flame is detected. 61.What is the role of a gas valve in HVAC systems? A) Control airflow B) Regulate fuel supply C) Measure voltage D) Filter air Correct Answer: B) Regulate fuel supply Rationale: Gas valves control gas flow to burners for heating.
62.What is duct static regain? A) Loss of refrigerant B) Pressure recovery in duct system C) Electrical gain D) Air filtering process Correct Answer: B) Pressure recovery in duct system Rationale: It refers to the recovery of pressure as air slows down in duct transitions. 63.What is psychrometric chart used for? A) Electrical testing B) Air property analysis C) Refrigerant charging D) Voltage measurement Correct Answer: B) Air property analysis Rationale: It helps analyze temperature, humidity, and enthalpy relationships in air. 64.What is enthalpy? A) Air velocity B) Total heat content C) Voltage level D) Refrigerant weight Correct Answer: B) Total heat content Rationale: Enthalpy represents both sensible and latent heat in air or refrigerant. 65.What is a VAV system? A) Variable Air Volume system B) Vapor Air Valve system
