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- What is the primary function of a refrigeration system? A. To create heat B. To move heat from one place to another C. To destroy humidity D. To generate electricity Answer: B Rationale: The refrigeration system does not “create cold”; it removes heat from a conditioned space and transfers it to another location, typically outside. This heat transfer process is the foundation of all HVAC cooling systems.
- Which refrigerant component absorbs heat in the evaporator? A. Compressor B. Condenser C. Expansion valve D. Refrigerant Answer: D Rationale: The refrigerant absorbs heat as it evaporates in the evaporator
coil, changing from liquid to vapor. This phase change allows it to carry thermal energy away from the indoor space.
- What is the function of the compressor? A. To cool refrigerant B. To increase refrigerant pressure C. To store refrigerant D. To filter moisture Answer: B Rationale: The compressor raises the pressure and temperature of the refrigerant vapor, enabling it to flow through the system and release heat in the condenser.
- Which device meters refrigerant into the evaporator? A. Compressor B. Expansion valve C. Condenser fan D. Receiver Answer: B Rationale: The expansion valve controls refrigerant flow and reduces its pressure before it enters the evaporator, allowing proper evaporation and heat absorption.
- What state is refrigerant leaving the condenser? A. Low-pressure vapor B. High-pressure liquid C. Low-pressure liquid D. Solid Answer: B
Rationale: The filter drier traps moisture, acids, and debris, protecting system components from corrosion and blockages.
- What does a thermostat control? A. Refrigerant pressure B. Temperature by cycling equipment C. Voltage output D. Air velocity Answer: B Rationale: A thermostat senses room temperature and signals HVAC equipment to turn on or off to maintain setpoint conditions. 10.What type of current is used in most HVAC motors? A. DC B. Single-phase AC C. Pulsating DC D. Solar current Answer: B Rationale: Most residential HVAC systems operate on single-phase alternating current, which is suitable for standard motors and compressors. 11.What is Ohm’s Law used for? A. Airflow calculation B. Electrical resistance, voltage, current relationship C. Refrigerant charging D. Pressure measurement Answer: B Rationale: Ohm’s Law defines the relationship between voltage, current, and resistance, essential for diagnosing electrical issues in HVAC systems.
12.What does a capacitor do in an HVAC motor circuit? A. Reduces airflow B. Stores electrical energy for motor start/run C. Increases refrigerant pressure D. Filters air Answer: B Rationale: Capacitors provide a phase shift and energy boost to start or run motors efficiently, especially in single-phase systems. 13.What is the purpose of a contactor? A. Measure pressure B. Switch high voltage circuits C. Cool refrigerant D. Filter air Answer: B Rationale: A contactor is an electrically controlled switch that energizes high-voltage components like compressors and condenser fans. 14.What is airflow measured in? A. PSI B. BTU C. CFM D. Volts Answer: C Rationale: Airflow in HVAC systems is measured in cubic feet per minute (CFM), indicating the volume of air moved. 15.What does a condenser do? A. Absorbs heat
Answer: B Rationale: Latent heat is energy absorbed or released during a phase change, such as evaporation or condensation, without temperature change. 19.What is sensible heat? A. Heat causing phase change B. Heat measured by temperature change C. Electrical resistance D. Pressure heat Answer: B Rationale: Sensible heat causes a measurable change in temperature without changing the substance’s state. 20.What is the purpose of duct insulation? A. Increase noise B. Prevent heat gain/loss C. Increase airflow resistance D. Reduce voltage Answer: B Rationale: Insulation minimizes unwanted heat transfer between duct air and surrounding environments, improving system efficiency. 21.What is static pressure in HVAC systems? A. Refrigerant force B. Resistance to airflow in ducts C. Electrical load D. Temperature difference Answer: B
Rationale: Static pressure represents resistance to airflow caused by duct design, filters, and components. 22.What tool measures electrical current? A. Thermometer B. Manometer C. Clamp meter D. Psychrometer Answer: C Rationale: A clamp meter measures current flow in a conductor without breaking the circuit. 23.What does a psychrometer measure? A. Voltage B. Humidity C. Refrigerant pressure D. Air velocity Answer: B Rationale: A psychrometer measures relative humidity using dry and wet bulb temperatures. 24.What is the purpose of a sight glass? A. Measure airflow B. Check refrigerant condition C. Increase pressure D. Filter oil Answer: B Rationale: A sight glass allows technicians to observe refrigerant condition, including bubbles or moisture indicators.
C. Airflow rate D. Voltage stability Answer: B Rationale: Combustion efficiency measures how effectively fuel is converted into usable heat. 29.What does a flame sensor do? A. Ignites gas B. Detects burner flame presence C. Measures airflow D. Controls refrigerant Answer: B Rationale: The flame sensor ensures gas valves remain open only when flame is detected for safety. 30.What is the function of a heat exchanger? A. Cool air B. Transfer heat between combustion gases and air C. Compress refrigerant D. Filter air Answer: B Rationale: Heat exchangers transfer heat from combustion gases to air without mixing them. 31.What causes frost on evaporator coils? A. High airflow B. Low refrigerant charge or airflow restriction C. High voltage D. Dirty condenser Answer: B
Rationale: Insufficient refrigerant or airflow causes coil temperature to drop below freezing, forming frost. 32.What is the purpose of a defrost cycle? A. Increase cooling B. Remove ice buildup C. Increase pressure D. Reduce voltage Answer: B Rationale: Defrost cycles melt ice on coils to maintain heat transfer efficiency. 33.What does a manifold gauge set measure? A. Airflow B. Refrigerant pressures C. Voltage D. Humidity Answer: B Rationale: It measures high and low side refrigerant pressures for system diagnostics. 34.What is a heat pump? A. Cooling-only system B. System that transfers heat in both directions C. Electrical heater D. Air filter Answer: B Rationale: Heat pumps can reverse refrigerant flow to provide heating or cooling.
D. Electrical switch Answer: B Rationale: A plenum distributes conditioned air evenly through duct systems. 39.What is duct leakage effect? A. Improved efficiency B. Reduced system efficiency C. Increased voltage D. Lower humidity Answer: B Rationale: Leaky ducts waste conditioned air, increasing energy consumption and reducing comfort. 40.What is the purpose of a return air system? A. Deliver fresh refrigerant B. Bring air back to HVAC system C. Increase pressure D. Reduce voltage Answer: B Rationale: Return air carries indoor air back to the system for reconditioning. 41.What is refrigerant saturation temperature? A. Temperature where phase change occurs B. Air temperature C. Electrical temperature D. Coil insulation level Answer: A
Rationale: Saturation temperature is where refrigerant changes between liquid and vapor at a given pressure. 42.What is the purpose of insulation on suction line? A. Prevent heat gain B. Increase pressure C. Reduce voltage D. Increase humidity Answer: A Rationale: Insulating suction lines prevents unwanted heat gain before refrigerant reaches compressor. 43.What does a circuit breaker protect against? A. Low airflow B. Overcurrent C. Refrigerant loss D. Heat gain Answer: B Rationale: Circuit breakers disconnect power during excessive current conditions to prevent damage or fire. 44.What is airflow restriction effect? A. Higher efficiency B. Reduced cooling/heating performance C. Higher voltage D. More humidity Answer: B Rationale: Restricted airflow reduces heat transfer and can cause system freezing or overheating.
D. Electrical grounding Answer: B Rationale: It removes water formed during dehumidification in cooling systems. 49.What is the purpose of a float switch? A. Measure airflow B. Shut system off when drain pan overflows C. Increase pressure D. Control refrigerant Answer: B Rationale: Float switches prevent water damage by shutting down the system during drainage failure. 50.What is HVAC system efficiency measured by? A. PSI B. SEER rating C. BTU only D. Voltage Answer: B Rationale: SEER (Seasonal Energy Efficiency Ratio) measures cooling efficiency over a season. CONTINUATION (51–100) 51.What is the purpose of a crankcase heater? A. Cool compressor B. Prevent refrigerant migration into oil C. Increase airflow
D. Reduce voltage Answer: B Rationale: It keeps refrigerant from mixing with compressor oil during off cycles, preventing damage on startup. 52.What causes high discharge pressure? A. Dirty condenser or overcharge B. Low airflow only C. Low voltage D. Clean coil Answer: A Rationale: Poor heat rejection or excess refrigerant increases system pressure on the discharge side. 53.What is a vacuum pump used for? A. Add refrigerant B. Remove air and moisture C. Increase pressure D. Test voltage Answer: B Rationale: It evacuates non-condensables and moisture before charging refrigerant. 54.What is the purpose of nitrogen during brazing? A. Increase heat B. Prevent oxidation C. Add refrigerant D. Increase pressure Answer: B
58.What is refrigerant recovery? A. Charging system B. Removing refrigerant for reuse or disposal C. Compressing gas D. Heating refrigerant Answer: B Rationale: Recovery safely removes refrigerant to prevent environmental release. 59.What is the purpose of a service valve? A. Measure voltage B. Access refrigerant system C. Increase airflow D. Heat system Answer: B Rationale: Service valves allow connection of gauges for testing and servicing. 60.What is a blower wheel imbalance cause? A. Smooth operation B. Vibration and noise C. Higher efficiency D. Lower pressure Answer: B Rationale: Uneven weight distribution causes mechanical vibration and system inefficiency. 61.What is duct velocity? A. Air speed in duct B. Refrigerant pressure
C. Voltage level D. Humidity level Answer: A Rationale: Velocity measures how fast air moves through ductwork, affecting comfort and noise. 62.What is an inducer motor purpose? A. Move refrigerant B. Exhaust combustion gases C. Increase voltage D. Filter air Answer: B Rationale: It ensures safe removal of combustion gases from heat exchanger. 63.What is combustion air? A. Return air B. Air used for burning fuel C. Refrigerant air D. Exhaust air only Answer: B Rationale: Combustion air supplies oxygen needed for fuel burning. 64.What is a pilot light? A. Electrical switch B. Small continuous flame C. Air filter D. Sensor Answer: B Rationale: It ignites main burners in older gas systems.
