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NCCER HVACR study materials
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NCCER HVACR practice questions

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Question 1Introduction to HVACR

In an HVACR context, what does the abbreviation HVACR stand for?

  1. Heating, Vacuum, Air Compression, and Refrigerant Recovery
  2. Heating, Venting, Air Cooling, and Recovery
  3. Heating, Ventilation, Air Conditioning, and Refrigeration Correct answer.
  4. Humidity, Ventilation, Airflow, and Cooling Regulation

Explanation

HVACR is the standard trade abbreviation for Heating, Ventilation, Air Conditioning, and Refrigeration. The added R distinguishes the trade from HVAC by explicitly including refrigeration systems such as walk-in coolers and display cases.

Question 2Introduction to HVACR

A technician measures the temperature of a room and records 72 degrees Fahrenheit. Which quantity has the technician measured?

  1. Dry-bulb temperature Correct answer.
  2. Wet-bulb temperature
  3. Relative humidity
  4. Sensible heat content of the air

Explanation

Dry-bulb temperature is the ordinary air temperature read by a standard thermometer, unaffected by moisture evaporation. Wet-bulb temperature would require a thermometer with a wetted wick and moving air, and it reads lower than dry bulb.

Question 3Introduction to HVACR

Which statement correctly describes the role of the compressor in a vapor-compression refrigeration system?

  1. It rejects heat from the refrigerant to the outdoor air.
  2. It absorbs heat from the conditioned space.
  3. It meters liquid refrigerant into the evaporator.
  4. It raises the pressure and temperature of refrigerant vapor. Correct answer.

Explanation

The compressor takes low-pressure vapor from the evaporator and discharges it at higher pressure, which also raises its saturation temperature so heat can be rejected in the condenser. Absorbing heat is the evaporator's job, and metering is the expansion device's job.

Question 4Introduction to HVACR

What is the primary purpose of ventilation in a residential HVACR system?

  1. To lower the dew point of the refrigerant
  2. To increase refrigerant pressure in the condenser
  3. To raise the heating capacity of the furnace
  4. To replace stale indoor air with outdoor air Correct answer.

Explanation

Ventilation introduces outdoor air and exhausts stale indoor air to control pollutants, odors, and moisture. It is separate from the heating and cooling functions, which condition air rather than exchange it.

Question 5Introduction to HVACR

A technician needs to measure the diameter of a copper refrigerant line to select the correct fitting. Which tool is designed for this measurement?

  1. Micrometer Correct answer.
  2. Refrigerant gauge manifold
  3. Flaring block
  4. Tubing cutter

Explanation

A micrometer measures small outside diameters precisely, which is needed to match tubing and fittings. Tubing cutters cut, flaring blocks form flare joints, and gauge manifolds read pressures.

Question 6Introduction to HVACR

Which of the following is a recognized safety hazard specific to handling refrigerant cylinders?

  1. Cylinders may rupture if heated, releasing refrigerant rapidly Correct answer.
  2. Cylinders must be stored upside down to prevent leakage
  3. Refrigerant is flammable at room temperature in all cases
  4. Refrigerant freezes at room temperature and blocks valves

Explanation

Refrigerant cylinders are pressure vessels; heating them raises internal pressure and can cause rupture or relief-valve discharge. Cylinders should be stored upright and kept away from heat sources.

Question 7Introduction to HVACR

A technician is converting a heat load expressed in Btu per hour to tons of refrigeration. How many Btu per hour equal one ton of refrigeration?

  1. 8,000
  2. 120,000
  3. 12,000 Correct answer.
  4. 1,000

Explanation

One ton of refrigeration is defined as 12,000 Btu per hour, the rate of heat removal needed to freeze one ton of ice in 24 hours. This conversion is used constantly when sizing equipment to a calculated load.

Question 8Introduction to HVACR

Which organization publishes the Safety Data Sheet that a technician should consult before using a chemical in the HVACR workplace?

  1. The local building department
  2. The equipment manufacturer only
  3. The chemical supplier or manufacturer Correct answer.
  4. The refrigerant reclaim facility

Explanation

The chemical manufacturer or supplier is required to provide a Safety Data Sheet describing hazards, handling, and first aid. It should be kept accessible to workers who use the product.

Question 9Introduction to HVACR

In a sealed refrigeration circuit, what is the function of the metering device?

  1. It removes moisture and acid from the refrigerant.
  2. It stores excess refrigerant during low-load conditions.
  3. It compresses vapor to a higher pressure.
  4. It creates a pressure drop that feeds low-pressure liquid refrigerant to the evaporator. Correct answer.

Explanation

The metering device restricts flow, dropping refrigerant pressure so it enters the evaporator at a low saturation temperature and can absorb heat. Compression, filtration, and storage are handled by other components.

Question 10Introduction to HVACR

A technician reads 0 psig on a gauge manifold connected to a system that should be pressurized. Which conclusion is most reasonable?

  1. The system charge is exactly correct.
  2. The compressor is operating at peak efficiency.
  3. The gauge may be connected to the wrong port or the system may be empty. Correct answer.
  4. The refrigerant is superheated.

Explanation

A zero reading on a pressurized system suggests the gauge is not actually sensing system pressure or the system has lost its charge. The technician should verify hose connections and valve positions before drawing conclusions about the charge.

Question 11Introduction to HVACR

Why is nitrogen used when pressure-testing a refrigeration system instead of compressed air?

  1. Nitrogen raises the system pressure faster than air.
  2. Nitrogen is cheaper than air.
  3. Nitrogen dissolves in refrigerant to boost capacity.
  4. Nitrogen is dry and inert, avoiding moisture and combustion risks. Correct answer.

Explanation

Nitrogen is dry and inert, so it does not introduce moisture that could form acid or ice, and it will not support combustion. Compressed air can carry moisture and, with oil present, create a hazard under high pressure.

Question 12Introduction to HVACR

A technician is brazing copper refrigerant lines. Which practice best protects the inside of the tubing from oxidation?

  1. Purge the line with dry nitrogen during brazing Correct answer.
  2. Cap both ends and braze without any flow
  3. Increase the acetylene pressure to maximum
  4. Wet the tubing with water before heating

Explanation

A low flow of dry nitrogen displaces oxygen inside the tubing while it is heated, preventing carbon and oxide scale from forming. Scale can later clog the metering device and contaminate the compressor.

Question 13Introduction to HVACR

A customer reports that the air conditioner runs but the house stays warm. The technician finds the outdoor condenser fan not turning while the compressor runs. What is the most likely immediate effect?

  1. The thermostat will lose calibration.
  2. High-side pressure will rise and the compressor may overheat. Correct answer.
  3. The evaporator will freeze rapidly.
  4. The refrigerant charge will increase.

Explanation

Without condenser airflow, heat cannot be rejected, so discharge pressure climbs and current draw rises, risking compressor overheating or trip. The system must be shut down and the fan circuit diagnosed.

Question 14Introduction to HVACR

Which statement best explains why refrigerant must be recovered rather than vented to the atmosphere?

  1. Recovery removes the need for a filter drier.
  2. Venting is prohibited because refrigerants deplete ozone or contribute to climate change. Correct answer.
  3. Venting increases the system's refrigerant capacity.
  4. Recovery improves the compressor's efficiency.

Explanation

Federal regulations prohibit knowingly venting ozone-depleting refrigerants and many substitute refrigerants because of environmental harm. Recovery equipment captures refrigerant for reuse, recycling, or reclamation.

Question 15Introduction to HVACR

A technician is calculating heat load for a small office and knows the room volume, the desired temperature difference, and a heat-transfer factor. Which formula gives the sensible heat load in Btu per hour?

  1. Q = volume divided by the temperature difference
  2. Q = volume multiplied by temperature difference multiplied by the factor Correct answer.
  3. Q = temperature difference divided by volume
  4. Q = volume plus temperature difference

Explanation

Sensible load is estimated by multiplying the volume of the space, the design temperature difference, and an appropriate heat-transfer factor. The result is expressed in Btu per hour and then compared with equipment capacity.

Question 16Introduction to HVACR

What distinguishes a packaged rooftop unit from a split system?

  1. A packaged unit serves only heating loads.
  2. A packaged unit contains all major components in one cabinet. Correct answer.
  3. A packaged unit uses no refrigerant.
  4. A packaged unit has no compressor.

Explanation

A packaged unit houses the compressor, condenser, evaporator, and blower in a single cabinet, while a split system separates indoor and outdoor sections connected by refrigerant lines. Both types use a vapor-compression cycle.

Question 17Introduction to HVACR

A technician notices frost forming on the suction line and the evaporator coil of a residential system. Which condition is most consistent with this symptom?

  1. High outdoor ambient temperature
  2. Overcharge of refrigerant
  3. Low airflow across the evaporator Correct answer.
  4. Failed condenser fan motor

Explanation

Restricted airflow, such as a dirty filter or blocked coil, lowers evaporator temperature below freezing and causes frost. Low charge can also cause freezing, so the technician should check airflow and superheat before adding refrigerant.

Question 18Introduction to HVACR

Which personal protective equipment is most important when a technician opens a refrigerant circuit that may contain liquid refrigerant?

  1. Rubber apron and respirator
  2. Dust mask and hard hat
  3. Hearing protection and steel-toe boots
  4. Safety glasses and insulated gloves Correct answer.

Explanation

Liquid refrigerant can cause frostbite on skin and severe eye injury, so safety glasses or goggles and insulated gloves are essential. Other PPE may be required for specific tasks but does not address the primary refrigerant exposure risk.

Question 19Introduction to HVACR

A technician is asked to explain why a heat pump can provide both heating and cooling. Which explanation is accurate?

  1. It reverses refrigerant flow with a reversing valve to swap the roles of the coils. Correct answer.
  2. It uses a separate furnace coil for cooling.
  3. It changes the compressor speed to change the direction of heat flow.
  4. It burns fuel in summer and uses electricity in winter.

Explanation

A reversing valve redirects refrigerant so the indoor coil becomes the condenser in heating mode and the evaporator in cooling mode. The compressor always moves heat from the evaporator to the condenser; only the coil roles change.

Question 20Introduction to HVACR

A technician reads a suction pressure that corresponds to a saturation temperature of 40 degrees F and measures a suction line temperature of 52 degrees F. What is the superheat?

  1. 12 degrees F Correct answer.
  2. 40 degrees F
  3. 92 degrees F
  4. 52 degrees F

Explanation

Superheat is the difference between the actual suction line temperature and the saturation temperature at the measured pressure. Subtracting 40 from 52 gives 12 degrees F of superheat.

Question 21Introduction to HVACR

During a load calculation, a technician must account for heat gained through windows by solar radiation. Which term describes this load component?

  1. Conduction through the roof
  2. Infiltration latent load
  3. Solar gain Correct answer.
  4. Internal latent load

Explanation

Solar gain is heat transmitted or radiated into the space through glazing and sunlit surfaces. It is separate from conduction through opaque assemblies and from latent loads caused by moisture.

Question 22Introduction to HVACR

A technician finds that a compressor draws locked-rotor current and trips its overload shortly after start. Which diagnosis is most consistent with this behavior?

  1. The compressor is mechanically seized or has a shorted winding. Correct answer.
  2. The condensate drain is clogged.
  3. The thermostat is set too low.
  4. The air filter is slightly dirty.

Explanation

Locked-rotor current with a quick overload trip indicates the rotor cannot turn or the windings are shorted, so the motor never reaches running speed. Electrical and mechanical checks should confirm which condition exists before replacement.

Question 23Introduction to HVACR

A technician is comparing a thermostatic expansion valve with a fixed orifice metering device. Which statement correctly describes a difference?

  1. The TXV is used only on chillers, while the orifice is used only on furnaces.
  2. The fixed orifice eliminates the need for a filter drier.
  3. The TXV modulates flow to maintain superheat, while the fixed orifice does not. Correct answer.
  4. The fixed orifice maintains superheat, while the TXV does not.

Explanation

A thermostatic expansion valve uses a sensing bulb to adjust flow and hold superheat near a set value as load changes. A fixed orifice provides a constant restriction, so superheat varies with conditions.

Question 24Introduction to HVACR

A technician must determine whether a system is overcharged or has a restricted liquid line. Which pair of readings would most help distinguish these conditions?

  1. Suction pressure and indoor temperature only
  2. Subcooling and the temperature drop across the liquid line Correct answer.
  3. Outdoor humidity and thermostat setpoint
  4. Compressor amp draw and furnace gas pressure

Explanation

High subcooling with a temperature drop across the liquid line points to a restriction, while high subcooling without a drop suggests overcharge. Comparing both readings separates the two conditions before any refrigerant is removed.

Question 25Introduction to HVACR

A technician is evacuating a system with a vacuum pump and a micron gauge. Why is the vacuum held and monitored after the pump is valved off?

  1. To test the compressor windings
  2. To confirm the system holds a deep vacuum without a leak or moisture boil-off Correct answer.
  3. To increase the refrigerant charge
  4. To calibrate the manifold gauges

Explanation

A standing vacuum test shows whether pressure rises because of a leak or because moisture is still boiling off inside the system. A stable reading indicates the system is dry and tight before charging.

Question 26Introduction to HVACR

Which career path within HVACR focuses primarily on installing and servicing the equipment that heats and cools a building's air?

  1. Refrigeration technician
  2. Heating, ventilation, air conditioning, and refrigeration mechanic Correct answer.
  3. Sheet metal worker
  4. Stationary engineer

Explanation

The HVACR mechanic installs, maintains, and repairs the heating, cooling, and ventilation equipment serving a building's comfort systems. Sheet metal workers fabricate and install ductwork, refrigeration technicians specialize in commercial cooling and food storage, and stationary engineers operate large central plants, so each covers a narrower or different scope.

Question 27Introduction to HVACR

Which document should a technician consult to learn the flash point, health hazards, and required handling precautions for a chemical used on the job?

  1. The refrigerant pressure-temperature chart
  2. The building occupancy permit
  3. The equipment nameplate
  4. The Safety Data Sheet Correct answer.

Explanation

The Safety Data Sheet, formerly the Material Safety Data Sheet, is the standardized document that lists a chemical's hazards, physical properties, and safe handling requirements. Nameplates give electrical ratings, occupancy permits describe building use, and pressure-temperature charts relate saturation pressure to temperature, so none of them reports chemical safety information.

Question 28Introduction to HVACR

Which statement accurately describes the difference between heat and temperature?

  1. Heat and temperature both measure the total energy contained in a substance
  2. Heat is measured in degrees Fahrenheit, while temperature is measured in British thermal units
  3. Heat is a form of energy, while temperature is a measure of the average molecular motion of a substance Correct answer.
  4. Heat is a measure of molecular motion, while temperature is the total energy transferred between objects

Explanation

Heat is energy in transit, measured in British thermal units or joules, while temperature indicates the average kinetic energy of the molecules in a substance. A large cool object can contain more total heat than a small hot object, which shows the two quantities are not interchangeable.

Question 29Introduction to HVACR

In the refrigeration cycle, which component adds heat to the refrigerant by absorbing it from the conditioned space?

  1. The condenser
  2. The compressor
  3. The evaporator Correct answer.
  4. The metering device

Explanation

The evaporator is the indoor coil where low-pressure liquid refrigerant boils and absorbs heat from the air moving across it, producing the cooling effect. The condenser rejects heat outdoors, the compressor raises pressure and temperature, and the metering device drops pressure to feed the evaporator.

Question 30Introduction to HVACR

Which unit of measurement is used to express the cooling capacity of a residential air conditioning system?

  1. Tons of refrigeration Correct answer.
  2. Cubic feet per minute
  3. Pounds per square inch gauge
  4. Inches of mercury

Explanation

Cooling capacity is commonly stated in tons of refrigeration, where one ton equals 12,000 Btu per hour. Cubic feet per minute measures airflow, inches of mercury measures vacuum, and pounds per square inch gauge measures pressure, so those units describe other system quantities.

Question 31Introduction to HVACR

Which type of drawing would a technician use to locate the refrigerant piping, duct routing, and equipment layout of a commercial building?

  1. A ladder diagram
  2. An electrical schematic
  3. A wiring diagram
  4. A mechanical drawing Correct answer.

Explanation

Mechanical drawings, also called mechanical plans, show the location and routing of HVACR equipment, piping, and ductwork within a building. Electrical schematics, ladder diagrams, and wiring diagrams describe control circuits and electrical connections rather than physical equipment layout.

Question 32Introduction to HVACR

A technician is about to climb a ladder to service a rooftop unit. Which practice best reduces the risk of a fall?

  1. Standing on the top two rungs to reach higher
  2. Leaning the ladder at a steep angle against the curb
  3. Facing the ladder and maintaining three points of contact Correct answer.
  4. Carrying tools in both hands while climbing

Explanation

Maintaining three points of contact while facing the ladder keeps the climber balanced and supported at all times. Carrying loads in both hands, standing on the top rungs, and setting an improper ladder angle all increase the chance of a fall.

Question 33Introduction to HVACR

Which statement best describes the purpose of the Clean Air Act Section 608 certification for technicians who service refrigerants?

  1. It certifies that a technician can weld refrigerant piping
  2. It establishes requirements for the safe handling and recovery of ozone-depleting refrigerants Correct answer.
  3. It sets minimum efficiency ratings for new air conditioning equipment
  4. It licenses a technician to perform electrical work on HVACR equipment

Explanation

Section 608 of the Clean Air Act sets rules for handling refrigerants, including certification, recovery, and prohibition of venting. It does not cover welding qualifications, equipment efficiency standards, or electrical licensing, which are governed by other rules and trades.

Question 34Introduction to HVACR

A technician is converting a cooling capacity given in tons to British thermal units per hour. How many Btu per hour equal one ton of refrigeration?

  1. 3,412
  2. 12,000 Correct answer.
  3. 25,000
  4. 1,200

Explanation

One ton of refrigeration equals 12,000 Btu per hour, the rate at which one ton of ice absorbs heat while melting over 24 hours. The other values reflect unrelated conversions such as watts to Btu or a smaller fraction of a ton.

Question 35Introduction to HVACR

A technician measures an air pressure of 0.5 inch of water column across a filter. Which statement correctly describes the relationship between this reading and the system's airflow resistance?

  1. The reading represents the absolute pressure of the air inside the duct
  2. The reading represents the velocity of the air in feet per minute
  3. The reading represents the temperature drop across the filter
  4. The reading represents the pressure difference that the blower must overcome to move air through the filter Correct answer.

Explanation

Inches of water column measure the small pressure differences used in air systems, and a reading taken across a filter indicates the resistance that the blower must overcome. Absolute duct pressure, air velocity, and temperature drop are separate measurements with different instruments and units.

Question 36Introduction to HVACR

A technician is comparing a belt-driven blower with a direct-drive blower. Which statement correctly describes a characteristic of the belt-driven design?

  1. The blower requires no periodic belt inspection
  2. The blower always operates at a single fixed speed
  3. The blower wheel mounts directly on the motor shaft
  4. The blower speed can be adjusted by changing pulley sizes Correct answer.

Explanation

A belt-driven blower uses a motor pulley, a belt, and a blower pulley, so changing pulley sizes alters the blower speed and airflow. Direct-drive blowers mount the wheel on the motor shaft and often use multi-speed motors, and belt-driven units require routine belt inspection and tensioning.

Question 37Introduction to HVACR

A technician is selecting a refrigerant for a new system and reviews its saturation curve. What does the saturation temperature of a refrigerant represent at a given pressure?

  1. The temperature at which liquid and vapor exist in equilibrium Correct answer.
  2. The temperature at which the refrigerant becomes a solid
  3. The temperature at which the refrigerant is entirely superheated vapor
  4. The temperature at which the refrigerant has no pressure

Explanation

At saturation, liquid and vapor phases coexist in equilibrium, and the saturation temperature corresponds to the pressure of the refrigerant. Above that temperature the refrigerant is superheated vapor, below it the refrigerant is subcooled liquid, and solid formation is not part of normal system operation.

Question 38Introduction to HVACR

A technician is using a gauge manifold during a service call. Which practice is correct for connecting the manifold to the system?

  1. Leave the hoses loosely connected to allow air to enter
  2. Connect the high-pressure hose to the low-side service port
  3. Purge the hoses with refrigerant before connecting them to the service ports Correct answer.
  4. Open both manifold valves fully before attaching the hoses

Explanation

Purging the hoses with a small amount of refrigerant before connecting them minimizes the air and moisture introduced into the system. Loose connections, cross-connecting high and low hoses, and opening both valves before attachment all allow contamination or unsafe flow.

Question 39Introduction to HVACR

A technician notices that the supply air temperature of a system is lower than expected while the airflow appears normal. Which condition is most consistent with this observation?

  1. A low refrigerant charge Correct answer.
  2. A restricted liquid line
  3. A dirty condenser coil
  4. A failed condenser fan motor

Explanation

A low refrigerant charge reduces the amount of heat absorbed in the evaporator, producing a lower supply air temperature, and it often appears with a low suction pressure and superheat that is higher than normal. A restricted liquid line, a dirty condenser coil, or a failed condenser fan motor would typically raise head pressure and produce different symptoms.

Question 40Introduction to HVACR

A technician is explaining the function of the compressor in a vapor-compression system. Which statement is accurate?

  1. It raises the pressure and temperature of the refrigerant vapor so heat can be rejected in the condenser Correct answer.
  2. It controls the amount of refrigerant that enters the evaporator
  3. It lowers the pressure of the refrigerant so it can absorb heat in the evaporator
  4. It removes moisture from the refrigerant before it enters the metering device

Explanation

The compressor takes low-pressure vapor from the evaporator and raises its pressure and temperature so that the refrigerant is hotter than the outdoor air and can reject heat in the condenser. Pressure reduction is the job of the metering device, moisture removal is handled by filter driers, and flow control belongs to the metering device.

Question 41Introduction to HVACR

Which safety practice is correct when a technician works with a torch to braze refrigerant lines near combustible material?

  1. Rely on the building sprinkler system for protection
  2. Use a fire extinguisher only after the flame spreads
  3. Keep a fire watch and a suitable extinguisher at the work area Correct answer.
  4. Begin brazing before the area is cleared of combustibles

Explanation

Hot-work procedures require removing or protecting combustibles and keeping a fire watch with the proper extinguisher available during and after the work. Waiting for a fire to spread, depending on sprinklers, or brazing before clearing the area all violate accepted hot-work safety practice.

Question 42Introduction to HVACR

A technician is asked to describe the difference between a ton of refrigeration and a ton of air conditioning capacity. Which statement is accurate?

  1. A ton of air conditioning capacity equals 1,000 Btu per hour
  2. A ton of refrigeration applies only to commercial equipment
  3. A ton of refrigeration equals 12,000 Btu per hour, while air conditioning capacity is measured only in kilowatts
  4. They are two names for the same 12,000 Btu per hour capacity Correct answer.

Explanation

A ton of refrigeration and a ton of air conditioning capacity both equal 12,000 Btu per hour and are used interchangeably in the trade. The other statements misstate the definition or incorrectly restrict the unit to particular equipment.

Question 43Introduction to HVACR

A technician is using a voltmeter to check a control circuit. Which practice is correct for measuring voltage across a component?

  1. Connect the meter in parallel with the component Correct answer.
  2. Connect the meter in series with the component
  3. Set the meter to the resistance range
  4. Disconnect the meter leads before power is applied

Explanation

Voltage is a difference in potential, so the meter must be connected in parallel across the component being tested. Series connection is used for current measurement, the resistance range is used with power off, and removing the leads defeats the purpose of the test.

Question 44Introduction to HVACR

A technician is checking a split system and finds that the indoor coil is clean, the filter is new, and the blower operates, yet the airflow at the registers is low. Which additional item should the technician check first?

  1. The refrigerant charge
  2. The duct system for restrictions or disconnections Correct answer.
  3. The compressor windings
  4. The thermostat setpoint

Explanation

When the indoor coil, filter, and blower are all in good condition but airflow remains low, the duct system is the next likely cause, including crushed or disconnected ducts and closed dampers. Refrigerant charge, compressor windings, and thermostat setpoint affect cooling performance or operation but not the volume of air delivered.

Question 45Introduction to HVACR

A technician is comparing a reciprocating compressor with a scroll compressor. Which statement correctly describes a characteristic of the scroll design?

  1. It uses a single rotating vane inside a cylinder
  2. It uses a piston and connecting rod to compress vapor
  3. It compresses vapor between two interlocking spiral members Correct answer.
  4. It requires a belt drive to operate

Explanation

A scroll compressor uses two interlocking spiral members, one fixed and one orbiting, to compress refrigerant vapor continuously. Pistons and connecting rods belong to reciprocating compressors, belt drives describe some open-drive arrangements, and a rotating vane describes a rotary compressor.

Question 46Introduction to HVACR

A technician is reviewing the electrical nameplate of a condensing unit before installing a disconnect. Which information is essential for selecting the correct branch-circuit protection?

  1. The duct static pressure
  2. The minimum circuit ampacity and maximum fuse or breaker rating Correct answer.
  3. The refrigerant charge in ounces
  4. The supply air temperature rise

Explanation

The nameplate lists minimum circuit ampacity and maximum overcurrent protection, which together determine the conductor size and the fuse or breaker rating permitted for the unit. Refrigerant charge, air temperature rise, and static pressure are performance data and do not govern electrical protection.

Question 47Introduction to HVACR

A technician is diagnosing a system in which the suction pressure is low, the superheat is high, and the evaporator is only partially frosted near the inlet. Which condition best explains these readings?

  1. A restriction in the metering device Correct answer.
  2. A failed condenser fan motor
  3. An overcharge of refrigerant
  4. A dirty condenser coil

Explanation

A restriction in the metering device limits refrigerant flow into the evaporator, which lowers suction pressure, raises superheat, and produces frost only where the small amount of refrigerant enters the coil. An overcharge raises suction pressure and lowers superheat, while a dirty condenser coil or failed condenser fan motor raises head pressure and does not produce these evaporator symptoms.

Question 48Introduction to HVACR

A technician is interpreting a set of readings in which the suction line is warm and the suction pressure is high while the evaporator coil is not uniformly cold. Which condition is most consistent with these readings?

  1. An undercharge of refrigerant
  2. A restriction in the liquid line
  3. A dirty evaporator coil
  4. A compressor with worn valves Correct answer.

Explanation

Worn compressor valves allow hot discharge vapor to leak back into the suction side, raising suction pressure and suction line temperature while reducing the system's ability to cool the coil evenly. An undercharge or liquid line restriction lowers suction pressure, and a dirty evaporator coil restricts airflow rather than raising suction pressure.

Question 49Introduction to HVACR

A technician is explaining why a heat pump's reversing valve allows the system to switch between heating and cooling. Which statement best describes the effect of the valve?

  1. It changes the speed of the compressor to match the load
  2. It reverses the rotation of the indoor blower motor
  3. It changes the direction of refrigerant flow so the indoor coil becomes the condenser in heating mode Correct answer.
  4. It bypasses the metering device during heating operation

Explanation

The reversing valve redirects refrigerant flow so that the indoor coil rejects heat in the heating mode and absorbs heat in the cooling mode. Compressor speed, metering device bypass, and blower rotation are controlled by other components and are not functions of the reversing valve.

Question 50Introduction to HVACR

A technician is comparing the pressure-enthalpy diagram with a simple saturation chart. Which statement correctly describes what the pressure-enthalpy diagram shows that the saturation chart does not?

  1. The electrical current drawn by the compressor
  2. The enthalpy change across each component and the state of the refrigerant throughout the cycle Correct answer.
  3. The airflow volume delivered by the blower
  4. The saturation temperature of the refrigerant at a single pressure

Explanation

A pressure-enthalpy diagram plots pressure against enthalpy and shows each state point and the enthalpy change across the evaporator, compressor, condenser, and metering device. A saturation chart relates pressure and temperature only, and neither chart reports compressor current or blower airflow.