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Question 1Fundamentals, Safety, and Tools

One ton of refrigeration is equivalent to which rate of heat removal?

  1. 3,412 Btu/hr
  2. 120,000 Btu/hr
  3. 1,200 Btu/hr
  4. 12,000 Btu/hr Correct answer.

Explanation

A ton of refrigeration is defined as the heat required to melt one ton of ice in 24 hours, which equals 200 Btu per minute or 12,000 Btu per hour. This number is used to size equipment and to convert capacity between tons and Btu/hr.

Question 2Fundamentals, Safety, and Tools

In a basic vapor-compression refrigeration cycle, refrigerant leaving the evaporator travels next to which component?

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

Explanation

Refrigerant absorbs heat and boils in the evaporator, then the low-pressure vapor is drawn into the compressor. From the compressor the hot high-pressure gas goes to the condenser, then through the metering device back to the evaporator.

Question 3Fundamentals, Safety, and Tools

On a standard two-valve manifold gauge set, which color identifies the center service hose?

  1. Yellow Correct answer.
  2. Blue
  3. Green
  4. Red

Explanation

The center hose is yellow and connects to a vacuum pump, recovery machine, or charging cylinder. The blue hose is the low-side connection and the red hose is the high-side connection.

Question 4Fundamentals, Safety, and Tools

Which personal protective equipment is appropriate when opening a circuit that may contain liquid refrigerant?

  1. A full-face respirator with supplied air
  2. Safety glasses and refrigerant-resistant gloves Correct answer.
  3. Cotton work gloves and a dust mask
  4. Hearing protection only

Explanation

Liquid refrigerant flashes to very low temperatures and can splash, causing frostbite and eye injury. Safety glasses plus insulated, refrigerant-resistant gloves protect the two most commonly injured areas; a dust mask and cotton gloves offer no protection against cold liquid.

Question 5Fundamentals, Safety, and Tools

Which method is an acceptable first check for a suspected leak at a flare connection?

  1. Holding an open flame near the joint
  2. Loosening the flare nut to see if gas escapes
  3. Brushing soap solution on the joint under pressure Correct answer.
  4. Pressurizing with oxygen and listening for a hiss

Explanation

Soap bubble solution applied to a pressurized joint is a simple, safe way to confirm a leak because escaping gas forms visible bubbles. Oxygen and open flames must never be used on a refrigerant system because of fire and decomposition hazards.

Question 6Fundamentals, Safety, and Tools

A technician must confirm that a 240 V disconnect is de-energized before servicing. Which meter function is appropriate?

  1. Diode test
  2. Continuity (resistance) with the circuit energized
  3. Capacitance
  4. AC voltage Correct answer.

Explanation

Absence of voltage is verified on the AC voltage range using a meter rated for the circuit voltage, ideally after proving the meter on a known live source. Resistance and other passive functions must never be used on an energized circuit.

Question 7Fundamentals, Safety, and Tools

After cutting copper tubing with a tubing cutter, what step should be taken before making a flare or braze joint?

  1. Ream the burr from the inside of the tube Correct answer.
  2. Coat the end with thread sealant
  3. Flatten the end with a hammer
  4. Sand the outside of the tube with coarse sandpaper

Explanation

A tubing cutter leaves a raised burr on the inside of the tube that restricts flow and can break loose into the system. Reaming removes the burr while keeping the cut square, which is essential for a clean flare or braze joint.

Question 8Fundamentals, Safety, and Tools

Heat moving along a solid copper rod from the warm end to the cool end is an example of which heat transfer method?

  1. Conduction Correct answer.
  2. Evaporation
  3. Radiation
  4. Convection

Explanation

Conduction is heat transfer through direct molecular contact within a solid material, so energy travels along the rod from warmer to cooler molecules. Convection requires a moving fluid, radiation travels as electromagnetic waves, and evaporation is a phase change.

Question 9Fundamentals, Safety, and Tools

Superheat is the difference between the actual suction line temperature and which other value?

  1. The condensing saturation temperature
  2. The outdoor ambient temperature
  3. The evaporating saturation temperature Correct answer.
  4. The liquid line temperature

Explanation

Superheat compares the measured suction line temperature to the saturation temperature that corresponds to the suction pressure. The difference shows how far the vapor has risen above saturation, which confirms the evaporator is fully fed with liquid.

Question 10Fundamentals, Safety, and Tools

Subcooling is determined by comparing the liquid line temperature to which value?

  1. The condensing saturation temperature Correct answer.
  2. The suction line temperature
  3. The evaporating saturation temperature
  4. The return air wet-bulb temperature

Explanation

Subcooling equals the condensing saturation temperature taken from the high-side pressure minus the measured liquid line temperature. A positive subcooling value confirms a solid column of liquid is reaching the metering device.

Question 11Fundamentals, Safety, and Tools

A typical residential split system is considered adequately evacuated when the standing vacuum holds at or below approximately which level?

  1. 5,000 microns
  2. 10,000 microns
  3. 500 microns Correct answer.
  4. 1,500 microns

Explanation

Deep evacuation targets 500 microns or lower, held without rise during a decay test, because lower absolute pressure is needed to boil off moisture. Microns measure absolute pressure, so a smaller number indicates a deeper vacuum.

Question 12Fundamentals, Safety, and Tools

Why is dry nitrogen flowed through tubing while it is being brazed?

  1. To increase the refrigerant charge capacity
  2. To cool the joint so the filler does not melt
  3. To keep oxygen out and prevent internal oxidation Correct answer.
  4. To pressurize the line for a leak check

Explanation

A slow nitrogen purge displaces oxygen inside the tubing so copper oxide scale cannot form during brazing. Scale flakes can clog metering devices, plug filter-driers, and damage the compressor.

Question 13Fundamentals, Safety, and Tools

A recovery cylinder should never be filled beyond what percentage of its capacity by weight?

  1. 50%
  2. 60%
  3. 80% Correct answer.
  4. 100%

Explanation

Department of Transportation recovery cylinders are limited to 80% fill by weight to leave room for liquid expansion as temperature rises. Overfilling can cause hydraulic pressure to rupture the cylinder.

Question 14Fundamentals, Safety, and Tools

Before handling a run capacitor removed from a circuit, a technician should:

  1. Rinse it in water to remove refrigerant oil
  2. Test it with a continuity tester while energized
  3. Discharge it through a resistor Correct answer.
  4. Assume it is discharged once power is off

Explanation

Capacitors store energy and can hold a dangerous charge after power is removed. Bleeding the terminals through an insulated resistor rated for the voltage safely dissipates that stored energy.

Question 15Fundamentals, Safety, and Tools

A 24 V control circuit supplies a relay coil with 12 ohms of resistance. What current flows through the coil?

  1. 0.5 A
  2. 12 A
  3. 2 A Correct answer.
  4. 288 A

Explanation

Ohm's law gives current as voltage divided by resistance: 24 volts divided by 12 ohms equals 2 amperes. This relationship is the basis for checking control circuit loading and fuse sizing.

Question 16Fundamentals, Safety, and Tools

As air is cooled with no moisture added or removed, the temperature at which it reaches saturation is called the:

  1. Wet-bulb temperature
  2. Approach temperature
  3. Dry-bulb temperature
  4. Dew point temperature Correct answer.

Explanation

The dew point is the temperature at which a given moisture content saturates the air, so further cooling causes condensation. It is a key value for predicting condensate on coils and duct surfaces.

Question 17Fundamentals, Safety, and Tools

Which instrument is used to measure static pressure in a duct when checking external static pressure?

  1. Infrared thermometer
  2. Manometer Correct answer.
  3. Micron gauge
  4. Clamp-on ammeter

Explanation

A manometer measures very small pressure differences and reads in inches of water column, which is the unit used for duct static pressure. External static pressure indicates how hard the blower is working and whether airflow is restricted.

Question 18Fundamentals, Safety, and Tools

Which practice correctly applies lockout/tagout before servicing a rooftop unit?

  1. Lock out the disconnect with your own lock and keep the key Correct answer.
  2. Remove the room thermostat from its wall plate
  3. Have a coworker stand by the disconnect and watch it
  4. Tape the disconnect switch so it cannot be moved

Explanation

Lockout/tagout requires isolating the energy source, applying a personal lock and tag, and verifying the unit is de-energized. Keeping the only key with the technician ensures no one else can restore power during the work.

Question 19Fundamentals, Safety, and Tools

What is the approved way to speed the transfer of refrigerant from a cylinder that is too cold?

  1. Cap the cylinder and lay it on its side in the sun
  2. Play an open torch flame on the cylinder bottom
  3. Warm the cylinder in a bucket of warm water Correct answer.
  4. Place the cylinder in a pot of boiling water

Explanation

Warm water raises the cylinder pressure gradually and safely so refrigerant flows to the recovery or charging equipment. Cylinder temperature should stay well below the rating stamped on the vessel, and flames or steam are never used.

Question 20Fundamentals, Safety, and Tools

What is the most reliable way to tighten a flare nut on a refrigerant line?

  1. Overtighten slightly to guarantee a seal
  2. Tighten until the tubing starts to twist
  3. Use a torque wrench set to the spec Correct answer.
  4. Tighten by hand only

Explanation

Manufacturers publish a torque value that deforms the flare just enough to seal without cracking it. A torque wrench removes guesswork, because both under-tightening and over-tightening cause leaks.

Question 21Fundamentals, Safety, and Tools

A refrigerant classified as A2L under ASHRAE Standard 34 is best described as:

  1. Higher toxicity and high flammability
  2. Higher toxicity and no flame propagation
  3. Lower toxicity and high flammability
  4. Lower toxicity and low flammability Correct answer.

Explanation

The letter designates toxicity, with A meaning lower toxicity and B meaning higher toxicity, while the number describes flammability. Class 2L means mildly flammable with a low burning velocity, distinguishing it from class 1 (no flame propagation) and class 3 (highly flammable).

Question 22Fundamentals, Safety, and Tools

How does a zeotropic refrigerant blend behave in an operating evaporator?

  1. It changes composition only when charged as a liquid
  2. It boils at one constant temperature for a given pressure
  3. It boils over a range, with different bubble and dew points Correct answer.
  4. It separates permanently into components in a sealed system

Explanation

Zeotropic blends change composition between the liquid and vapor phases, so boiling occurs across a temperature range. This glide means the bubble point (liquid) and dew point (vapor) pressures differ at the same temperature, and charging must account for it.

Question 23Fundamentals, Safety, and Tools

A combustion analyzer shows 300 ppm carbon monoxide in the flue of a gas furnace. What should the technician do?

  1. Shut the furnace down, correct the cause, then re-test Correct answer.
  2. Ignore it, since CO is always present in flue gas
  3. Raise the manifold gas pressure to dilute the CO
  4. Record the reading and check again next season

Explanation

Flue CO this high signals incomplete combustion from dirty burners, wrong gas pressure, or a compromised heat exchanger and is an immediate safety concern. The unit should be taken out of service, the cause corrected, and the repair verified with the analyzer before returning it to operation.

Question 24Fundamentals, Safety, and Tools

Why must a container of polyolester (POE) oil be kept sealed and used promptly once opened?

  1. It absorbs moisture from the air, forming acids Correct answer.
  2. It reacts with copper to form acid sludge in air
  3. It loses lubricity when exposed to nitrogen
  4. It solidifies permanently at room temperature

Explanation

POE oil is highly hygroscopic, so it pulls moisture out of the air quickly. Moisture plus POE plus heat produces acids and sludge that attack motor windings and plug capillaries, which is why containers are kept sealed and capped with dry nitrogen.

Question 25Fundamentals, Safety, and Tools

Which compressor type is commonly used in large centrifugal water chillers because of its high volumetric capacity?

  1. Reciprocating
  2. Rotary vane
  3. Centrifugal Correct answer.
  4. Scroll

Explanation

Centrifugal compressors move very large volumes of vapor at relatively low pressure ratios, which suits the high tonnage of large chilled water plants. The other designs are positive-displacement machines better matched to smaller capacities.

Question 26Fundamentals, Safety, and Tools

One ton of refrigeration is equal to which rate of heat removal?

  1. 12,000 Btu/h Correct answer.
  2. 3,412 Btu/h
  3. 120,000 Btu/h
  4. 1,200 Btu/h

Explanation

One ton of refrigeration is defined as the heat removal rate needed to freeze one ton of ice in 24 hours, which equals 12,000 Btu/h. It describes a rate of heat transfer, not a temperature or a refrigerant quantity.

Question 27Fundamentals, Safety, and Tools

Which eye protection is appropriate for oxyacetylene brazing?

  1. Ordinary clear safety glasses
  2. Goggles with filter lenses for gas welding Correct answer.
  3. A disposable dust mask
  4. A face shield without filter lenses

Explanation

Brazing produces intense visible light, ultraviolet and infrared radiation, and sparks. Filter lenses protect the eyes from radiation and flying debris.

Question 28Fundamentals, Safety, and Tools

Which instrument measures air velocity inside a duct?

  1. Manometer
  2. Micron gauge
  3. Anemometer Correct answer.
  4. Clamp meter

Explanation

An anemometer measures air velocity, often in feet per minute. A manometer measures pressure, a micron gauge measures vacuum, and a clamp meter measures current.

Question 29Fundamentals, Safety, and Tools

Adding sensible heat to a substance produces which result?

  1. A phase change at constant temperature
  2. A temperature rise without a change of state Correct answer.
  3. A decrease in total heat content
  4. A pressure increase with no temperature change

Explanation

Sensible heat changes the temperature of a substance without changing its state. Latent heat is associated with phase changes at essentially constant temperature.

Question 30Fundamentals, Safety, and Tools

How should a refrigerant cylinder be secured during normal use?

  1. Balanced on a sloped surface
  2. Inverted with the valve at the bottom
  3. Lying flat on its side
  4. Upright and fastened to prevent tipping Correct answer.

Explanation

Refrigerant cylinders should remain upright and secured so they cannot tip, roll, or be damaged. This also keeps the valve protected and helps ensure the correct phase is withdrawn.

Question 31Fundamentals, Safety, and Tools

A micron gauge is used to measure which condition?

  1. Duct static pressure
  2. Air velocity at a register
  3. Refrigerant weight in a cylinder
  4. Vacuum level during evacuation Correct answer.

Explanation

A micron gauge measures absolute pressure in the deep-vacuum range during system evacuation. It is far more sensitive than a standard manifold gauge for this purpose.

Question 32Fundamentals, Safety, and Tools

Before measuring resistance with a multimeter, the technician should do which step?

  1. Leave the circuit energized
  2. Connect the leads across a live capacitor
  3. Set the meter to the volts function
  4. De-energize and isolate the circuit Correct answer.

Explanation

An ohmmeter supplies its own small voltage to measure resistance, so the circuit must be de-energized and isolated. Testing a live circuit can damage the meter and produce false readings.

Question 33Fundamentals, Safety, and Tools

Which tool is used to expand the end of copper tubing so it can accept another tube of the same size?

  1. Torque wrench
  2. Flaring block
  3. Tubing cutter
  4. Swaging tool Correct answer.

Explanation

A swaging tool expands the end of copper tubing to form a slip joint for brazing. A flaring block forms a cone-shaped flare for a flare fitting instead.

Question 34Fundamentals, Safety, and Tools

Moisture in air condenses on a cooling coil. The heat removed during this phase change is called what?

  1. Superheat
  2. Latent heat Correct answer.
  3. Sensible heat
  4. Specific heat

Explanation

Latent heat is the heat absorbed or released during a change of state without a temperature change. Condensation releases latent heat as water vapor becomes liquid.

Question 35Fundamentals, Safety, and Tools

An electric heater adds 10,000 Btu/h to an airstream with a 20°F temperature rise. What airflow is required? Use the sensible heat equation 1.08 × CFM × ΔT.

  1. 463 CFM Correct answer.
  2. 46 CFM
  3. 231 CFM
  4. 926 CFM

Explanation

Rearranging the sensible heat equation gives CFM = Btu/h ÷ (1.08 × ΔT). Substituting gives 10,000 ÷ (1.08 × 20), which is approximately 463 CFM.

Question 36Fundamentals, Safety, and Tools

At sea level, standard atmospheric pressure is approximately which value?

  1. 101.3 psig
  2. 0 psig
  3. 14.7 psia Correct answer.
  4. 29.92 psig

Explanation

Standard atmospheric pressure at sea level is about 14.7 psia, which equals 0 psig. It is also equivalent to 29.92 inches of mercury absolute or 101.3 kPa absolute.

Question 37Fundamentals, Safety, and Tools

When dry nitrogen is used to pressure-test a system, the regulator should be set up in which way?

  1. Adjusted to the required test pressure and fitted with a relief valve Correct answer.
  2. Removed so full cylinder pressure is available
  3. Set to cylinder pressure
  4. Bypassed with a charging hose

Explanation

A pressure regulator reduces the high cylinder pressure to the required test pressure. A relief valve protects the system and hoses from accidental overpressurization.

Question 38Fundamentals, Safety, and Tools

When using an electronic refrigerant leak detector, the probe should be moved in which manner?

  1. Only after adding leak dye to the system
  2. Quickly through the entire room
  3. Slowly along suspected joints Correct answer.
  4. Only at the compressor service valve

Explanation

Electronic leak detectors need time to sample the air and respond to refrigerant concentration. Moving the probe slowly near joints, fittings, and coils improves detection.

Question 39Fundamentals, Safety, and Tools

A 120 V circuit draws 5 A. What is the resistance of the circuit?

  1. 0.042 Ω
  2. 125 Ω
  3. 24 Ω Correct answer.
  4. 600 Ω

Explanation

Ohm's law states that resistance equals voltage divided by current. Dividing 120 V by 5 A gives 24 Ω.

Question 40Fundamentals, Safety, and Tools

Two 10 Ω resistors are connected in series across a 24 V source. What current flows?

  1. 12 A
  2. 0.83 A
  3. 1.2 A Correct answer.
  4. 2.4 A

Explanation

In series, resistances add, so the total resistance is 20 Ω. Ohm's law then gives 24 V ÷ 20 Ω = 1.2 A.

Question 41Fundamentals, Safety, and Tools

For a saturated refrigerant, what does the pressure-temperature relationship determine?

  1. It is the same for every refrigerant
  2. It fixes the saturation pressure at a given temperature Correct answer.
  3. It applies only to superheated vapor
  4. It changes with ambient temperature

Explanation

At saturation, a refrigerant has a fixed pressure for each temperature. This relationship allows technicians to use gauges to infer saturation temperatures and to evaluate superheat and subcooling.

Question 42Fundamentals, Safety, and Tools

Which meter function is used to test a capacitor's microfarad rating?

  1. Capacitance function Correct answer.
  2. Frequency function
  3. DC volts function
  4. Continuity function

Explanation

A multimeter with a capacitance function measures the capacitor in microfarads for comparison with its rating. The capacitor must be discharged and isolated before testing.

Question 43Fundamentals, Safety, and Tools

Contact between liquid refrigerant and exposed skin can cause which injury?

  1. Permanent hearing loss
  2. Lead poisoning
  3. A minor rash only
  4. Frostbite and tissue damage Correct answer.

Explanation

Liquid refrigerant boils at a very low temperature and rapidly absorbs heat from skin. This can freeze tissue and cause severe frostbite or cold burns.

Question 44Fundamentals, Safety, and Tools

Relative humidity is best defined as which quantity?

  1. The heat content of moist air
  2. The amount of moisture in air compared with the maximum it can hold at that temperature Correct answer.
  3. The temperature at which air becomes saturated
  4. The total weight of water vapor in a pound of dry air

Explanation

Relative humidity compares the actual water vapor present with the maximum the air could hold at the same temperature. It is expressed as a percentage and changes as temperature changes.

Question 45Fundamentals, Safety, and Tools

A clamp-on ammeter is used to measure which electrical value?

  1. Capacitance of a motor
  2. Resistance of a winding
  3. Voltage across a load
  4. Current without opening the circuit Correct answer.

Explanation

A clamp-on ammeter measures current by sensing the magnetic field around a conductor. The conductor is clamped inside the jaws, so the circuit does not need to be opened.

Question 46Fundamentals, Safety, and Tools

A space gains 24,000 Btu/h sensible heat and 6,000 Btu/h latent heat. What is the sensible heat ratio?

  1. 1.20
  2. 0.80 Correct answer.
  3. 0.25
  4. 0.75

Explanation

Sensible heat ratio is sensible heat divided by total heat. Total heat is 24,000 + 6,000 = 30,000 Btu/h, so the SHR is 24,000 ÷ 30,000 = 0.80.

Question 47Fundamentals, Safety, and Tools

Two 12 Ω resistors are connected in parallel across a 24 V source. What total current does the source supply?

  1. 4 A Correct answer.
  2. 1 A
  3. 0.5 A
  4. 2 A

Explanation

Each branch has 24 V across 12 Ω, so each draws 2 A. In parallel, the branch currents add, giving a total of 4 A.

Question 48Fundamentals, Safety, and Tools

Air is heated with no moisture added or removed. Which statement describes the result?

  1. Relative humidity falls and dew point stays the same Correct answer.
  2. Relative humidity rises and dew point rises
  3. Relative humidity stays the same and dew point rises
  4. Relative humidity falls and dew point falls

Explanation

Heating air increases its capacity to hold moisture, so relative humidity falls even though the moisture content is unchanged. Because no moisture is added or removed, the dew point remains constant.

Question 49Fundamentals, Safety, and Tools

A 30 A circuit breaker protects a continuous load. Using the 80% rule, what maximum continuous current is permitted?

  1. 18 A
  2. 36 A
  3. 24 A Correct answer.
  4. 30 A

Explanation

For continuous loads, the load should not exceed 80% of the breaker rating. Multiplying 30 A by 0.80 gives 24 A.

Question 50Fundamentals, Safety, and Tools

Why should oxygen never be used to pressure-test a refrigeration system?

  1. It freezes the compressor oil
  2. It is too costly for field use
  3. It can explode when mixed with oil Correct answer.
  4. It changes the color of the refrigerant

Explanation

Oxygen supports combustion and can form an explosive mixture with compressor oil or other hydrocarbons. Dry nitrogen is used instead because it is inert and does not support combustion.