3e151 CDC Set C/P Volume 1

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1.  Refrigerants containing chlorine are said to destroy

Explanation

Refrigerants containing chlorine are known to destroy ozone. This is because chlorine atoms can break apart ozone molecules in the stratosphere, resulting in a depletion of the ozone layer. This process is known as ozone depletion. The destruction of ozone can have harmful effects on the environment and human health, as it allows more ultraviolet (UV) radiation from the sun to reach the Earth's surface. Therefore, it is important to use refrigerants that do not contain chlorine to prevent further damage to the ozone layer.

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About This Quiz
3e151 CDC Set C/P Volume 1 - Quiz

The '3E151 CDC Set C\/P Volume 1' quiz assesses knowledge on refrigeration systems, focusing on components, heat types, and system processes. It tests understanding of practical HVAC applications,... see morecrucial for professionals in mechanical engineering and related fields. see less

2. What must you do to the power before you perform a preoperational check on a heating, ventilation, air-conditioning, and refrigeration (HVAC/R) system?

Explanation

To perform a preoperational check on an HVAC/R system, it is necessary to turn off the power and confirm it with a meter. This ensures that the system is completely shut down and there is no electrical current flowing through it, allowing for a safe inspection and maintenance. Using a meter helps to verify that the power is indeed off and prevents any accidental electrical shock or damage to the system during the check.

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3. Which evaporator operating condition uses air circulation to aid in defrosting?

Explanation

Defrosting is the evaporator operating condition that uses air circulation to aid in defrosting. During the defrosting process, the air circulation helps to melt the frost that has accumulated on the evaporator coils. This is typically achieved by temporarily reversing the direction of the refrigerant flow or by using electric heaters to warm the coils. The air circulation helps to distribute the warm air evenly across the coils, speeding up the defrosting process and ensuring efficient operation of the evaporator.

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4. What term refers to how hot or cold a substance is?

Explanation

Temperature refers to how hot or cold a substance is. It is a measure of the average kinetic energy of the particles in a substance. When the particles have higher kinetic energy, the substance is hotter, and when they have lower kinetic energy, the substance is colder. Temperature is commonly measured using various scales such as Celsius, Fahrenheit, or Kelvin.

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5. Which major component is considered to be the "heart" of the refrigeration system?

Explanation

The compressor is considered to be the "heart" of the refrigeration system because it is responsible for compressing the refrigerant gas, raising its pressure and temperature. This high-pressure gas is then sent to the condenser where it releases heat and becomes a high-pressure liquid. The compressor plays a crucial role in the refrigeration cycle by circulating the refrigerant and maintaining the flow of heat transfer throughout the system. Without the compressor, the refrigeration system would not be able to function properly.

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6. Which refrigeration compressor is equipped with pistons and connecting rods?

Explanation

A reciprocating refrigeration compressor is equipped with pistons and connecting rods. This type of compressor uses a piston-cylinder arrangement to compress the refrigerant by reciprocating motion. As the piston moves back and forth, it compresses the refrigerant gas, which is then discharged into the condenser. The reciprocating compressor is commonly used in small to medium-sized refrigeration and air conditioning systems due to its efficiency and reliability.

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7. The best criteria to follow when you are inspecting equipment are

Explanation

When inspecting equipment, it is best to follow the manufacturer's recommendations. This is because the manufacturer knows their equipment best and can provide specific guidelines for inspection, maintenance, and safety. These recommendations are based on extensive testing and research, ensuring that the equipment functions optimally and remains in good condition. By adhering to the manufacturer's recommendations, you can minimize the risk of damage, malfunctions, and accidents, ultimately prolonging the lifespan of the equipment and ensuring its proper functioning.

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8. All moving parts on an air compressor should have

Explanation

Guards should be installed on all moving parts of an air compressor to prevent accidents and injuries. Guards act as a protective barrier, preventing any contact between the moving parts and individuals nearby. They help to ensure the safety of the operators and anyone working in the vicinity of the air compressor. Without guards, there is a higher risk of accidents, such as entanglement or getting struck by the moving parts. Therefore, it is essential to have guards in place to maintain a safe working environment.

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9. What is the term for a refrigeration unit to operate or cycle on?

Explanation

The term "cut-in" refers to the point at which a refrigeration unit starts operating or cycling on. It indicates the temperature at which the unit begins to cool down the environment. This term is commonly used in the context of thermostats or temperature control systems, where the cut-in temperature is set to activate the refrigeration unit and maintain the desired temperature range.

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10.  The float assembly in an oil separator is activated by the

Explanation

The float assembly in an oil separator is activated by the level of the oil. This means that as the oil level rises, the float assembly is triggered and performs a specific action. This action could be signaling a control system to shut down the oil separator or activating a pump to remove excess oil. The float assembly serves as a crucial component in maintaining the proper oil level in the separator and preventing any potential issues that may arise from an overflow or insufficient oil level.

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11. Which of these refrigerants has an ozone depletion rating of zero?

Explanation

R-134a is the correct answer because it has an ozone depletion rating of zero. This means that it does not contribute to the depletion of the ozone layer. R-12 and R-22, on the other hand, have ozone depletion potentials and can harm the ozone layer. R-500 was not mentioned in relation to its ozone depletion rating, so it cannot be determined if it has a rating of zero or not.

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12. What must be balanced to distribute the load as equally as possible between multiple compressors?

Explanation

To distribute the load as equally as possible between multiple compressors, the refrigerant lines must be balanced. The refrigerant lines are responsible for carrying the refrigerant from the compressors to the evaporators and condensers. By ensuring that the refrigerant lines are balanced, the flow of refrigerant can be evenly distributed among the compressors, preventing any one compressor from being overloaded. This helps to optimize the performance and efficiency of the system, ensuring that each compressor operates at its optimal capacity.

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13. Two different metals that are bonded into a strip or coil are called

Explanation

When two different metals are bonded together to form a strip or coil, it is known as a bimetal. The prefix "bi-" indicates that there are two metals involved in the bonding process. This term is commonly used in engineering and manufacturing industries to describe materials with different thermal expansion properties, allowing them to be used in applications such as thermostats, electrical switches, and temperature sensors.

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14. You are retrofitting a system that does not have a receiver. To do the job properly, you would store the refrigerant in

Explanation

To retrofit a system without a receiver properly, the refrigerant should be stored in a recovery cylinder. A recovery cylinder is designed to safely store and transport refrigerant during the retrofitting process. It allows for the proper handling and disposal of the refrigerant, ensuring that it does not escape into the atmosphere and cause environmental harm. Storing the refrigerant in the compressor, condenser, or evaporator would not be appropriate or effective for the retrofitting process.

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15.  To create the required pressure drop, the capillary tube uses a designed

Explanation

The capillary tube creates the required pressure drop by using resistance. Resistance is the opposition to the flow of fluid through the tube, and by designing the capillary tube with a specific level of resistance, the desired pressure drop can be achieved. This resistance helps to regulate the flow rate and pressure of the fluid passing through the tube.

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16. Where do you install a sight glass and/or moisture indicator in a refrigeration system?

Explanation

A sight glass and/or moisture indicator is installed in the liquid line of a refrigeration system. This is because the liquid line carries the condensed refrigerant from the condenser to the expansion device. By installing the sight glass and/or moisture indicator in this location, technicians can easily monitor the flow of refrigerant and detect any presence of moisture or contaminants. This helps ensure the proper functioning and efficiency of the refrigeration system.

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17. The disadvantage of water-cooled condensers is

Explanation

Water-cooled condensers have the disadvantage of higher cost compared to other types of condensers. This is because water-cooled condensers require additional equipment such as cooling towers, pumps, and water treatment systems, which can increase the overall cost of the system. Additionally, the installation and maintenance of water-cooled condensers can be more expensive compared to air-cooled condensers, further contributing to their higher cost.

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18. What device is used to prevent liquid refrigerant from entering the compressor?

Explanation

The device used to prevent liquid refrigerant from entering the compressor is called an accumulator. The accumulator is located in the suction line of the refrigeration system and its main function is to separate any liquid refrigerant from the refrigerant vapor before it enters the compressor. This is important because the compressor is designed to compress vapor and not liquid. The accumulator collects any liquid refrigerant and allows it to evaporate before it reaches the compressor, ensuring that only vapor is being compressed.

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19. Which heat pump component prevents liquid refrigerant from entering the compressor?

Explanation

The accumulator is a heat pump component that prevents liquid refrigerant from entering the compressor. It is located between the evaporator and the compressor and its main function is to separate any remaining liquid refrigerant from the refrigerant vapor before it enters the compressor. This is important because if liquid refrigerant enters the compressor, it can cause damage to the compressor and affect the overall performance of the heat pump system. Therefore, the accumulator plays a crucial role in ensuring the proper functioning of the heat pump by preventing liquid refrigerant from entering the compressor.

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20. The direct-expansion evaporator picks up or absorbs heat directly from the

Explanation

The direct-expansion evaporator picks up or absorbs heat directly from the conditioned space. This means that the evaporator is located within the conditioned space, such as inside an air conditioning unit or a refrigeration system. It is responsible for absorbing heat from the air or the space being cooled, and transferring it to the refrigerant. This allows the refrigerant to evaporate and carry the heat away, resulting in a cooling effect in the conditioned space.

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21. What type of heat when added to a substance causes a measured temperature change without a change of state?

Explanation

Sensible heat refers to the type of heat that causes a measurable change in temperature without causing a change in the state of a substance. This means that when sensible heat is added to a substance, its temperature increases or decreases, but the substance remains in the same physical state (solid, liquid, or gas). Sensible heat transfer occurs due to the transfer of thermal energy between objects or substances with different temperatures, resulting in a measurable change in temperature.

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22. How much of the refrigerant charge should a receiver hold?

Explanation

The receiver in a refrigeration system is designed to hold the entire amount of refrigerant charge. This is because the receiver acts as a storage tank for the refrigerant, ensuring that there is always an adequate supply available for the system to operate efficiently. By holding the entire amount of refrigerant charge, the receiver helps to maintain proper refrigerant levels and prevent issues such as insufficient cooling or compressor damage.

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23. What is a big problem with humidity control equipment?

Explanation

Scale is a big problem with humidity control equipment. Scale refers to the accumulation of mineral deposits, such as calcium and magnesium, on the surfaces of the equipment. These deposits can restrict the flow of air and water, reducing the efficiency and effectiveness of the equipment. Scale buildup can also lead to corrosion and damage to the equipment over time. Therefore, it is important to regularly clean and maintain humidity control equipment to prevent scale formation and ensure optimal performance.

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24. On a centrifugal machine, the refrigerant flows from the first-stage impeller to the

Explanation

In a centrifugal machine, the refrigerant flows from the first-stage impeller to the second-stage impeller. This is because centrifugal machines typically have multiple stages, with each stage consisting of an impeller. The purpose of the impellers is to increase the pressure and velocity of the refrigerant. Therefore, after passing through the first-stage impeller, the refrigerant needs to flow to the second-stage impeller to undergo further compression and acceleration.

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25. On systems that contain over how many pounds of refrigerant is passive recovery not authorized?

Explanation

Passive recovery refers to the process of recovering refrigerant without the use of a recovery machine. It relies on the natural movement of refrigerant from a system to a recovery cylinder. According to the given answer, passive recovery is not authorized for systems that contain over 15 pounds of refrigerant. This means that for systems with more than 15 pounds of refrigerant, a recovery machine must be used to safely and efficiently recover the refrigerant.

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26.  The advantage of an air-cooled condenser is

Explanation

An air-cooled condenser has the advantage of requiring less maintenance compared to other types of condensers. This is because it does not require water or other external cooling sources, making it easier to maintain and reducing the need for regular inspections and repairs. Additionally, there are no concerns about water leaks or water treatment, further reducing the maintenance requirements.

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27. Which pressure control has contacts that open on a rise in pressure?

Explanation

A high-pressure safety switch is designed to open its contacts when the pressure rises above a certain threshold. This is a safety measure to prevent damage or malfunctioning of equipment or systems that operate under high pressure. By opening the contacts, the switch interrupts the circuit and stops the flow of current, thus preventing any further increase in pressure. This feature ensures the safety of the equipment and the surrounding environment by preventing overpressure situations.

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28. Which component is installed at the inlet of the evaporator?

Explanation

The metering device is installed at the inlet of the evaporator. This component is responsible for regulating the flow of refrigerant into the evaporator, ensuring that the correct amount of refrigerant enters the system. By controlling the flow, the metering device helps to maintain the desired temperature and pressure within the evaporator, allowing for efficient heat transfer and cooling.

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29. What triggers a refrigeration unit to cycle on or off?

Explanation

The control circuit is responsible for triggering the refrigeration unit to cycle on or off. It regulates the operation of the unit based on temperature settings or other control inputs. When the control circuit detects that the desired temperature has been reached, it will turn off the unit. Conversely, when the temperature rises above the set point, the control circuit will activate the refrigeration unit to cool the environment. The control circuit plays a crucial role in maintaining the desired temperature and ensuring efficient operation of the refrigeration unit.

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30. Temperature glide in an zeotropic refrigerant means that the refrigerant is a

Explanation

The correct answer is "blend that evaporates and condenses over a range of temperatures instead of a single temperature." Temperature glide refers to the phenomenon where a zeotropic refrigerant undergoes both evaporation and condensation over a range of temperatures, rather than at a single temperature. This is due to the presence of different components with varying boiling and condensing points in the refrigerant blend.

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31. What is the maximum fine and jail sentence that service technicians may be subject to for charging a system with an unacceptable refrigerant?

Explanation

Service technicians may be subject to a maximum fine of $25,000 and a jail sentence of 5 years for charging a system with an unacceptable refrigerant.

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32. Heat that is picked up in the refrigeration system is rejected at the

Explanation

In a refrigeration system, the condenser is responsible for the heat rejection process. After the refrigerant has absorbed heat from the evaporator, it enters the condenser where it releases the heat to the surrounding environment, typically through a set of coils or fins. This allows the refrigerant to cool down and return to a liquid state, ready to repeat the cooling cycle. Therefore, the correct answer is the condenser.

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33. Which processes take place inside the condenser?

Explanation

Inside the condenser, two processes occur: desuperheating and condensing. Desuperheating refers to the process of reducing the temperature of superheated vapor, while condensing involves the transformation of vapor into a liquid state. These processes are essential for the functioning of the condenser, as they help to remove heat from the vapor and convert it back into a liquid form, allowing for the efficient operation of the overall system.

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34. Which packaged unit normally uses only one fan motor?

Explanation

A window unit is a type of packaged unit that typically uses only one fan motor. Unlike other types of packaged units such as heat pumps, floor-mounted units, and central self-contained units, a window unit is designed to be installed in a window and is compact enough to cool or heat a single room. The use of only one fan motor in a window unit helps to keep the unit small and portable, making it a convenient option for cooling or heating small spaces.

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35. Which type of water-cooled condenser has removable heads that allow the tubes to be cleaned out with a revolving brush?

Explanation

A shell-and-tube water-cooled condenser has removable heads that allow the tubes to be cleaned out with a revolving brush. In this type of condenser, the water flows through the tubes while the refrigerant flows around the tubes in a shell. The removable heads make it easier to access and clean the tubes, ensuring efficient heat transfer between the refrigerant and the water.

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36. What is the line to inlet relationship of refrigerant vapor travel as it leaves the evaporator?

Explanation

The correct answer is "Suction to compressor." In a refrigeration system, the suction line connects the evaporator outlet to the compressor inlet. This line carries the low-pressure refrigerant vapor from the evaporator to the compressor, where it is compressed and sent to the condenser for further cooling. Therefore, the suction line is responsible for transporting the refrigerant vapor from the evaporator to the compressor.

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37. In a multi stage air-compressor installation, what is used to remove heat between the stages?

Explanation

Intercoolers are used to remove heat between the stages in a multi-stage air-compressor installation. These devices cool down the compressed air between each stage, preventing excessive heat buildup and reducing the overall temperature of the air. This cooling process improves the efficiency and performance of the compressor, as it allows for denser air to be compressed in the subsequent stages. Intercoolers are essential in maintaining the optimal operating conditions and preventing damage to the compressor.

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38. Complete vaporization in an evaporator occurs at point

Explanation

The correct answer is V because complete vaporization in an evaporator occurs at the vapor outlet point, where all the liquid has been evaporated and only vapor is present.

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39. Which alternative replacement for R–502 is a patented azeotrope?

Explanation

R-507 is a patented azeotrope alternative replacement for R-502. This means that R-507 is a mixture of two or more refrigerants that behave as a single substance, providing similar cooling properties as R-502. It is protected by a patent, indicating that it is a proprietary blend and cannot be replicated or used without permission. Therefore, R-507 is the correct answer as it meets the criteria of being a patented azeotrope replacement for R-502.

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40. How does the rotary compressor compress the refrigerant vapor?

Explanation

The rotary compressor compresses the refrigerant vapor through a squeezing action. This means that the compressor uses rotating action to squeeze the vapor, reducing its volume and increasing its pressure. As the vapor is squeezed, its molecules are forced closer together, resulting in a higher pressure. This process is essential for the efficient operation of the refrigeration system, as it allows the vapor to be condensed and cooled before being circulated again.

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41. What program is designed to keep heating, ventilation, air-conditioning, and refrigeration (HVAC/R) equipment in operational condition?

Explanation

A recurring maintenance program is designed to keep heating, ventilation, air-conditioning, and refrigeration (HVAC/R) equipment in operational condition. This program involves regularly scheduled inspections, cleaning, and repairs to ensure that the equipment is functioning properly and efficiently. By implementing a recurring maintenance program, potential issues can be identified and addressed before they become major problems, helping to extend the lifespan of the equipment and minimize downtime.

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42. Where are the coldest rooms located in a permanent cold-storage plant?

Explanation

The coldest rooms in a permanent cold-storage plant are located inside the facility. This is because the purpose of a cold-storage plant is to maintain a low temperature for preserving perishable items. Therefore, the coldest rooms are situated inside the plant to ensure that the desired temperature is maintained and that the stored items remain fresh and unspoiled.

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43. During retrofitting, which component might have to be reset to compensate for higher discharge pressures?

Explanation

During retrofitting, when higher discharge pressures are encountered, the high-pressure cutout might have to be reset. This is because the high-pressure cutout is designed to protect the system from excessive pressure, and if the discharge pressures are higher than normal after retrofitting, the cutout may need to be adjusted to prevent damage to the system.

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44. An ice-cream cabinet is similar to a

Explanation

An ice-cream cabinet is similar to a chest-type freezer because both have a similar design and function. A chest-type freezer typically has a hinged lid on top and a large storage space inside, allowing for easy access and efficient freezing of food items. Similarly, an ice-cream cabinet also has a similar design with a lid on top and is specifically designed to store and display ice cream products. Both the chest-type freezer and ice-cream cabinet provide a low temperature environment to keep the items inside frozen and preserved for a longer period of time.

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45.  Cleaning a refrigerant at the job site or at a local service shop is called

Explanation

The process of cleaning a refrigerant at the job site or at a local service shop is referred to as recycling. This involves removing any impurities or contaminants from the refrigerant to make it suitable for reuse. Recycling helps to minimize waste and conserve resources by extending the lifespan of the refrigerant, reducing the need for new refrigerant production.

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46.  When polyolester oil is used in place of mineral oil during a retrofit procedure, you must make sure that less than what percent of mineral oil can remain in the system?

Explanation

During a retrofit procedure, when polyolester oil is used instead of mineral oil, it is crucial to ensure that less than 5% of mineral oil remains in the system. This is because the two types of oils have different properties and mixing them can lead to issues such as reduced lubrication efficiency and potential damage to the system components. Therefore, it is important to thoroughly flush the system and remove as much mineral oil as possible before using polyolester oil.

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47.  Which organization requires that a comprehensive risk assessment be performed to estimate the likelihood of fire and potential results should a fire occur when alternative refrigerants contain a flammable component?

Explanation

The Environmental Protection Agency (EPA) requires a comprehensive risk assessment to be performed in order to estimate the likelihood of fire and potential results if a fire were to occur when alternative refrigerants contain a flammable component. This is because the EPA is responsible for regulating and enforcing environmental laws and regulations, including those related to the use and handling of hazardous substances such as refrigerants. By requiring a risk assessment, the EPA aims to ensure that proper safety measures are in place to prevent and mitigate the risks associated with flammable refrigerants.

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48. Proportionately which refrigerator has the biggest freezer compartment?

Explanation

The side-by-side refrigerator has the biggest freezer compartment compared to the other options. This type of refrigerator is designed with the freezer on one side and the refrigerator on the other side, providing equal space for both compartments. In contrast, the top-freezer refrigerator has a smaller freezer compartment located on the top, while the single-door refrigerator and bottom-freezer refrigerator have even smaller freezer compartments. Therefore, the side-by-side refrigerator offers the largest freezer space proportionately.

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49. The Environmental Protection Agency (EPA) has developed a Significant New Alternatives Policy (SNAP) Program. This program is used to determine

Explanation

The EPA's Significant New Alternatives Policy (SNAP) Program is developed to assess the risks that alternative refrigerants pose to human health and the environment. The program aims to determine whether the alternative refrigerant is safe and does not have adverse effects on human health or the environment. By evaluating the risks associated with alternative refrigerants, the EPA can make informed decisions on which refrigerants can be used as substitutes for harmful substances, promoting environmental protection and public health.

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50. The thermostatic expansion valve maintains a fully active evaporator by

Explanation

The thermostatic expansion valve is responsible for regulating the flow of refrigerant into the evaporator coil. It does this by sensing the temperature of the refrigerant leaving the evaporator and adjusting the size of the valve opening accordingly. By maintaining the proper amount of superheat, which is the temperature difference between the refrigerant vapor and its saturation temperature, the expansion valve ensures that the evaporator is operating efficiently. This helps to prevent the formation of liquid refrigerant in the evaporator, which can cause a loss of cooling capacity and potential damage to the compressor.

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51. How is the capillary tube in a system affected by the refrigerant charge?

Explanation

The refrigerant charge refers to the amount of refrigerant present in the system. If the charge is not at the correct level, it can have a significant impact on the performance of the system, including the capillary tube. The capillary tube is responsible for regulating the flow of refrigerant through the system. If the refrigerant charge is too high or too low, it can cause the capillary tube to become ineffective in controlling the flow, leading to issues such as improper cooling or inefficient operation. Therefore, it is crucial to ensure that the refrigerant charge is at the correct level for optimal system performance.

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52. What do filter-driers not remove from a refrigeration system?

Explanation

Filter-driers are components in a refrigeration system that are designed to remove contaminants such as acids, sludge, and moisture. However, they are not effective in removing sand. Sand particles are too large and heavy to be captured by the filter-drier. Therefore, while filter-driers are important for maintaining the cleanliness and efficiency of a refrigeration system, they do not have the ability to remove sand particles.

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53. In which two parts of a refrigeration system does a pressure change take place?

Explanation

In a refrigeration system, a pressure change takes place in the compressor and metering device. The compressor is responsible for compressing the refrigerant vapor, increasing its pressure and temperature. This high-pressure, high-temperature vapor then flows to the metering device, which reduces the pressure of the refrigerant and controls its flow rate into the evaporator. This pressure change is crucial for the refrigeration cycle to work effectively, as it allows the refrigerant to absorb heat in the evaporator and release it in the condenser.

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54. The reciprocating refrigeration compressor is designed to remove

Explanation

The reciprocating refrigeration compressor is designed to remove vapor refrigerant from the evaporator and increase the pressure. This is because the compressor plays a crucial role in the refrigeration cycle by compressing the low-pressure vapor refrigerant from the evaporator and raising its pressure. This high-pressure vapor refrigerant is then sent to the condenser where it can be condensed into a liquid state. Therefore, the correct answer is "vapor refrigerant from the evaporator and increase the pressure."

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55. What type of thermostatic expansion valve has a charged sensing bulb that presents the danger of flood-back?

Explanation

A thermostatic expansion valve with a charged sensing bulb that presents the danger of flood-back is a "Liquid" type. In this type of valve, the sensing bulb is filled with a liquid charge, which can cause flood-back if not properly controlled. Flood-back occurs when liquid refrigerant enters the compressor, leading to potential damage. Therefore, a liquid type thermostatic expansion valve requires careful monitoring and control to prevent flood-back.

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56. In which major component does absorbed heat cause liquid refrigerant to boil?

Explanation

The absorbed heat causes the liquid refrigerant to boil in the evaporator. The evaporator is responsible for absorbing heat from the surroundings, such as the air in a room, and this heat causes the liquid refrigerant to evaporate and turn into a gas. This gas then travels to the compressor where it is pressurized and sent to the condenser to release the heat before returning to the evaporator to repeat the cycle.

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57. What prevents direct impact of refrigerant vapors on the tubing bundle of the centrifugal system condenser?

Explanation

The baffle plate prevents direct impact of refrigerant vapors on the tubing bundle of the centrifugal system condenser. It acts as a barrier between the vapors and the tubing, redirecting the flow and preventing any potential damage or corrosion that could occur from direct contact.

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58. What is the maximum percent a refillable cylinder can be refilled with refrigerant?

Explanation

The maximum percent a refillable cylinder can be refilled with refrigerant is 80%. This means that the cylinder can be filled up to 80% of its total capacity with refrigerant. Refilling the cylinder beyond this limit may cause safety issues or damage to the cylinder. It is important to follow this guideline to ensure proper functioning and safety when handling refrigerants.

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59. What type of rotary compressor has the blade set into the cylinder?

Explanation

A rotary compressor with a stationary blade has the blade set into the cylinder. This means that the blade remains fixed in position while the cylinder rotates, allowing for the compression of air or gas. The stationary blade helps to create a seal and control the flow of the medium being compressed. This type of compressor is commonly used in various applications, including refrigeration and air conditioning systems.

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60. Which compressor type is used with refrigerants that have a large gas volume?

Explanation

Centrifugal compressors are used with refrigerants that have a large gas volume. These compressors are specifically designed to handle high flow rates and are efficient in compressing large volumes of gas. They work by converting kinetic energy into pressure energy, making them suitable for applications where a large gas volume needs to be compressed, such as in industrial refrigeration systems or large-scale air conditioning units.

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61. Which evaporator type is designed to maintain an even temperature throughout the refrigerated space?

Explanation

Forced-convection evaporators are designed to maintain an even temperature throughout the refrigerated space. This type of evaporator uses a fan or blower to circulate air over the evaporator coil, ensuring that the cold air is evenly distributed throughout the space. The forced convection helps to prevent any temperature variations, ensuring that all areas of the refrigerated space are kept at the desired temperature. This is particularly important in applications where temperature consistency is critical, such as in food storage or pharmaceuticals.

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62.  Which refrigerant oil is designed for use with the new ternary blend refrigerants?

Explanation

Alkyl benzene oil is designed for use with the new ternary blend refrigerants. It is a synthetic oil that offers excellent lubricity and stability, making it suitable for use in refrigeration systems. Alkyl benzene oil is compatible with various refrigerants, including the new ternary blend refrigerants, and helps to ensure efficient and reliable operation of the system.

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63. To help ensure that the proper refrigerant and lubricant will be used in a system in the future, you would

Explanation

Labeling the components and system is the correct answer because it helps ensure that the proper refrigerant and lubricant will be used in the future. By clearly labeling the components and system, technicians can easily identify the correct type and amount of refrigerant and oil to use, preventing any potential mistakes or accidents. This labeling system also helps in maintaining the system by providing important information about the components and their requirements, making it easier for future maintenance and repairs.

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64. Which desiccant is the most popular and can be left in the system indefinitely?

Explanation

Silica gel is the most popular desiccant that can be left in the system indefinitely. Silica gel is a highly porous substance that has a strong affinity for water molecules, making it an effective moisture absorber. It is widely used in various industries and applications, such as in food packaging, electronics, and pharmaceuticals. Its popularity stems from its ability to maintain its moisture-absorbing properties even after it becomes saturated, allowing it to be reused or regenerated easily. Additionally, silica gel is non-toxic and chemically inert, making it safe to use in various environments.

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65. During equipment cooling, humidity cannot be added to the air by

Explanation

Saturating the coils with warm water cannot add humidity to the air during equipment cooling because the water would not evaporate into the air. In order to add humidity, the water needs to evaporate and become water vapor. However, saturating the coils with warm water would simply result in the coils being wet, without any evaporation occurring. Therefore, this method does not add humidity to the air.

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66. In relation to the curve, where is the liquid refrigerant shown on the pressure-enthalpy (PE) chart?

Explanation

The liquid refrigerant is shown on the left side of the pressure-enthalpy (PE) chart. This is because the left side of the chart represents low pressure and low enthalpy conditions, which are characteristic of the liquid phase of the refrigerant. As the refrigerant evaporates and transitions into a gas, it moves towards the right side of the chart where the pressure and enthalpy values increase. Therefore, the correct answer is "Left".

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67. On a multi-evaporator system, the evaporator pressure regulating (EPR) valve will close when it reaches what temperature point?

Explanation

The EPR valve on a multi-evaporator system will close when it reaches the cutout temperature point. This means that when the evaporator pressure reaches a certain high temperature, the EPR valve will close to prevent further increase in pressure. This helps to maintain the desired operating conditions and prevent damage to the system.

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68. Which type piston can suction gas pass through?

Explanation

A trunk piston is designed with a cavity or trunk in the center, allowing the gas to pass through it. This type of piston is commonly used in internal combustion engines, where the gas needs to flow through the piston during the intake stroke. The trunk design enables efficient suction of the gas into the combustion chamber. Therefore, a trunk piston is the correct type of piston that allows gas to pass through.

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69. Air intake filters used on air compressors are designed to prevent

Explanation

Air intake filters used on air compressors are designed to prevent unnecessary wear by filtering out particles and contaminants from the air before it enters the compressor. These particles can cause abrasion and damage to the internal components of the compressor, leading to increased wear and reduced performance. By keeping the air clean, the intake filter helps to maintain the efficiency and longevity of the compressor by reducing the risk of unnecessary wear on its parts.

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70. What is it called when two or more compressors are piped in series to one another?

Explanation

When two or more compressors are piped in series to one another, it is called compounding. This means that the output of the first compressor is fed into the input of the second compressor, and so on. This allows for increased compression and pressure in the system, as each compressor adds to the overall compression. Compounding is commonly used in industrial applications where high levels of compression are required.

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71. Which type of ice-machine evaporator produces a slab of ice that is moved onto a hot-wire grid?

Explanation

A horizontal plate ice-machine evaporator produces a slab of ice that is moved onto a hot-wire grid. The horizontal plate design allows for the ice to be formed in a flat, even layer on the evaporator surface. Once the ice is fully formed, it is then moved onto a hot-wire grid where it is cut into individual slabs. This design is commonly used in ice-making machines for commercial and industrial applications where large quantities of ice are needed.

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72. In relation to the curve, where does the refrigerant change of state take place on the pressure-enthalpy (PE) chart?

Explanation

The refrigerant change of state takes place inside the curve on the pressure-enthalpy (PE) chart. This means that the change from liquid to vapor or vice versa occurs within the boundaries of the curve, indicating a transition between different states of the refrigerant.

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73. Where does the compressed refrigerant vapor go during the heating cycle on a heat pump?

Explanation

During the heating cycle on a heat pump, the compressed refrigerant vapor goes to the evaporator. The evaporator is responsible for absorbing heat from the surrounding air or water, causing the refrigerant to evaporate and turn into a gas. This gas then travels to the compressor, where it is further compressed and heated, eventually releasing the heat into the desired space. So, the evaporator is the correct answer as it is the component where the refrigerant vapor goes during the heating cycle.

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74. Which cooler is used exclusively to cool liquids?

Explanation

The Baudelot cooler is used exclusively to cool liquids. This type of cooler is specifically designed to efficiently cool liquids by circulating them through a series of tubes or coils. The liquid flows through the tubes while a cooling medium, such as water or air, passes over the exterior of the tubes, extracting heat and cooling the liquid. This design allows for effective heat transfer and cooling of the liquid, making the Baudelot cooler ideal for applications where liquid cooling is required.

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75. What condition must exist before using a pressure-temperature (PT) chart?

Explanation

Before using a pressure-temperature (PT) chart, the condition that must exist is that the substance being analyzed should be in a saturated state. A saturated substance is one where it exists in equilibrium with both its liquid and vapor phases at a given temperature and pressure. This is important because the PT chart provides information about the relationship between pressure and temperature for a specific substance in its saturated state, allowing for accurate calculations and analysis.

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76. The receiver tanks used on air compressors are designed to be

Explanation

The receiver tanks used on air compressors are designed to be air storage tanks. These tanks store compressed air that is generated by the compressor, allowing for a steady supply of air to be available for use when needed. They help to regulate the pressure and flow of the compressed air, ensuring that it is readily available for various applications.

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77. On Type II systems, what level of evacuation in the isolated component must be attained when you are making minor repairs of items such as a filter-drier or a strainer?

Explanation

When making minor repairs on Type II systems, such as replacing a filter-drier or a strainer, the isolated component must be evacuated to a level of 0 pounds per square inch gauge (psig). This means that the component should be completely free of any pressure. This is necessary to ensure that there are no contaminants or moisture left in the system, which could affect its performance. Evacuating the component to 0 psig helps maintain the efficiency and reliability of the system.

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78. R–401A is not a suitable alternative refrigerant for

Explanation

R-401A is not a suitable alternative refrigerant for residential air conditioners because it is primarily designed for low-temperature applications, such as walk-in coolers and supermarket display cases. Residential air conditioners require a refrigerant that is specifically formulated for higher operating temperatures and pressures. Using R-401A in residential air conditioners could lead to inefficient cooling, potential damage to the system, and increased energy consumption.

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79. What factor is not part of the known factors for using a pressure-temperature (PT) chart?

Explanation

The known factors for using a pressure-temperature (PT) chart include ambient temperature, type of refrigerant, and vapor pressure. Humidity level is not a part of the known factors for using a PT chart. The PT chart is used to determine the relationship between pressure and temperature for a specific refrigerant, and humidity level does not directly affect this relationship.

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80. You are retrofitting a system with an alternative refrigerant and you determine that the capillary tube must be replaced. To do the job correctly, you would replace the capillary tube with one having

Explanation

When retrofitting a system with an alternative refrigerant, replacing the capillary tube with one having greater resistance and longer length is the correct approach. A capillary tube controls the flow of refrigerant into the evaporator coil. By increasing the resistance and length of the capillary tube, the flow rate of the refrigerant is reduced. This is necessary when using an alternative refrigerant, as it may have different pressure and flow characteristics compared to the original refrigerant. Adjusting the capillary tube in this way ensures proper functioning of the system with the new refrigerant.

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81. When manual condensate drains are installed on an air receiver tank, they should be checked

Explanation

Manual condensate drains on an air receiver tank should be checked daily to ensure that any accumulated condensate is properly drained. Regular and frequent checks are necessary to prevent the buildup of excess condensate, which can lead to corrosion and damage to the tank and the compressed air system. By checking the drains daily, any issues or blockages can be promptly addressed, ensuring the efficient operation of the system.

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82. You have plotted all the points for an operating refrigeration system on a pressure-enthalpy (PE) chart. This will not show you the

Explanation

Plotting all the points for an operating refrigeration system on a pressure-enthalpy (PE) chart allows us to analyze various properties and characteristics of the system. However, it does not provide information about the gained system pressure. The gained system pressure refers to the increase in pressure that occurs within the refrigeration system due to factors such as resistance in the flow of refrigerant or the operation of compressors. This information is not directly visible or measurable from the pressure-enthalpy chart.

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83. Commercial and industrial systems with leaks exceeding what percent per year will require repair?

Explanation

Commercial and industrial systems with leaks exceeding 35% per year will require repair. This means that if the leaks in the system exceed 35% of the total volume per year, it is necessary to fix the leaks. This is because leaks can lead to significant loss of resources and can also cause damage to the system itself. Therefore, it is important to address and repair any leaks that exceed this threshold to ensure the proper functioning and efficiency of the commercial or industrial system.

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84. What accessory is added to the cascade system to increase its efficiency?

Explanation

A heat exchanger is added to the cascade system to increase its efficiency. A heat exchanger is a device that transfers heat between two or more fluids, allowing them to exchange thermal energy. In a cascade system, the heat exchanger helps to improve the efficiency by transferring heat from the high-temperature refrigerant to the low-temperature refrigerant. This allows for a more efficient transfer of heat and helps to optimize the cooling process. By using a heat exchanger, the cascade system can effectively utilize the temperature difference between the two refrigerants, resulting in improved overall efficiency.

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85. The economizer on a centrifugal machine prevents liquid refrigerant from entering the compressor through the use of

Explanation

The economizer on a centrifugal machine prevents liquid refrigerant from entering the compressor through the use of eliminator baffles. These baffles are designed to separate the liquid refrigerant from the vapor refrigerant, allowing only the vapor to enter the compressor. By preventing liquid refrigerant from entering the compressor, the economizer helps to maintain the efficiency and performance of the centrifugal machine.

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86. What type maintenance action do you perform on operating heating, ventilation, air-conditioning, and refrigeration (HVAC/R) system?

Explanation

Performing an operational check on an operating HVAC/R system involves assessing its functionality and performance. This includes testing the various components, such as the thermostat, fans, motors, and refrigerant levels, to ensure they are working properly. By conducting this check, any issues or malfunctions can be identified and addressed promptly, helping to maintain the system's efficiency and prevent potential breakdowns. It is an essential maintenance action to ensure the smooth operation of the HVAC/R system.

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87. Which type of compressor uses an orbiting motion for compression?

Explanation

A scroll compressor uses an orbiting motion for compression. It consists of two spiral-shaped scrolls, one fixed and one orbiting, which creates a series of gas pockets that gradually decrease in size, compressing the gas. This design allows for smooth and efficient compression without the need for valves, making scroll compressors quieter and more reliable compared to other types of compressors.

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88. The ultralow-temperature classification begins at

Explanation

The ultralow-temperature classification begins at -20*F because this temperature is significantly lower than the other options provided (-10*F, -5*F, and 0*F). Ultralow temperatures refer to extremely cold conditions, and -20*F falls within this range.

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89. The hydraulic cylinder unloader mechanism is designed to unload the cylinder by holding the

Explanation

The hydraulic cylinder unloader mechanism is designed to unload the cylinder by holding the suction valve open. This means that the mechanism allows the fluid to flow out of the cylinder through the suction valve, relieving the pressure and unloading the cylinder. By keeping the suction valve open, the mechanism ensures that the fluid can flow freely and efficiently, preventing any potential damage or malfunction in the cylinder.

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90. When conducting an operational check of the mechanical part of a heating, ventilation, air-conditioning, and refrigeration (HVAC/R) system, you should check

Explanation

When conducting an operational check of the mechanical part of an HVAC/R system, it is important to check the system pressures. This is because the system pressures indicate whether the system is functioning properly and if there are any issues such as leaks or blockages. By monitoring the system pressures, technicians can ensure that the system is operating at the correct levels and make any necessary adjustments or repairs. Checking the water levels, cleanliness of coils, and proper lubrication are also important maintenance tasks, but they are not directly related to the operational check of the mechanical part of the system.

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91. Which display-cabinet defrosting method has the advantage of not being affected by changes in ambient temperature?

Explanation

Hot-wire defrosting method has the advantage of not being affected by changes in ambient temperature. This is because hot-wire defrosting relies on an electric resistance wire that heats up to melt the ice on the display-cabinet. The temperature of the wire is controlled independently of the ambient temperature, ensuring consistent and efficient defrosting regardless of external conditions.

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92. Which item is not an advantage of a multiple-compressor system?

Explanation

A multiple-compressor system is designed to have multiple compressors operating in parallel, which allows for partial operation in case of failure of one unit. This redundancy ensures that the system can continue to function even if one compressor fails. Economy of operation at low loads is also an advantage of a multiple-compressor system, as it allows the system to adjust its capacity based on the demand, resulting in energy savings. Control of refrigeration effect is another advantage, as it allows for precise temperature control. However, lower humidity levels are not an advantage of a multiple-compressor system.

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93. When the compressor air intake is piped to the outside, it should be

Explanation

The compressor air intake should be six feet above the ground to prevent it from drawing in debris, dust, or water that may be present on the ground. Placing it at this height ensures that the air being sucked into the compressor is clean and free from any potential contaminants that could damage the equipment or affect its performance.

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94. A retrofitted air-conditioning system still has the original capillary tube installed. In addition, the unit is undercharged with R–401A. In this configuration, the unit will operate satisfactorily in

Explanation

In this configuration, the retrofitted air-conditioning system with the original capillary tube and undercharged with R-401A will operate satisfactorily in relatively constant ambient conditions. This means that the system is designed to work efficiently in conditions where the temperature and humidity of the surrounding environment remain relatively stable. Fluctuating ambient conditions may cause the system to struggle to maintain the desired temperature and humidity levels, leading to reduced performance and potential issues. Therefore, it is important to ensure that the system is properly sized and charged for the specific ambient conditions it will be operating in.

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95. Which pressure control is designed to cut in on a rise in pressure and cut out on a drop in pressure?

Explanation

A low-pressure motor control is designed to cut in on a rise in pressure and cut out on a drop in pressure. This means that when the pressure drops below a certain threshold, the motor control will activate and start the motor, and when the pressure rises above a certain threshold, the motor control will deactivate and stop the motor. This ensures that the motor only operates within the desired pressure range, preventing any damage or malfunction due to excessive pressure.

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96. To regulate the load on a water-cooled condenser, you should

Explanation

To regulate the load on a water-cooled condenser, controlling the tower fan is the correct answer. The tower fan helps in dissipating the heat from the condenser by drawing air through the cooling tower. By controlling the speed or operation of the tower fan, the amount of air passing through the tower can be adjusted, thereby regulating the cooling effect on the condenser. This allows for efficient cooling and helps maintain the desired temperature and load on the condenser.

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97. What type of thermostatic expansion valve has a bulb that is charged with fluid that is different from the refrigerant in the system?

Explanation

A cross type thermostatic expansion valve has a bulb that is charged with fluid that is different from the refrigerant in the system. This allows for more precise control of the refrigerant flow as the fluid in the bulb expands and contracts with temperature changes, providing accurate feedback to the valve. This type of valve is commonly used in systems where precise temperature control is required.

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98. Which of these refrigerants is colorless and has a very pronounced odor?

Explanation

R-717, also known as ammonia, is a colorless refrigerant with a very pronounced odor. It is commonly used in industrial refrigeration systems due to its high efficiency and low environmental impact. Ammonia has a strong smell that is easily detectable, even in small concentrations, which makes it a safe choice as any leaks can be quickly identified.

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99. Approximately what percent of the evaporator tubing bundle is covered by the normal refrigerant charge in the centrifugal machine?

Explanation

The correct answer is 50. This means that approximately 50% of the evaporator tubing bundle is covered by the normal refrigerant charge in the centrifugal machine.

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100. R-406a can be used to replace

Explanation

R-406a can be used to replace R-12 because R-12 is a hydrochlorofluorocarbon (HCFC) refrigerant that has been phased out due to its harmful effects on the ozone layer. R-406a is a blend of refrigerants that does not contain any ozone-depleting substances and has similar properties to R-12. Therefore, it can be used as a suitable alternative to R-12 in various refrigeration and air conditioning systems.

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101. You have plotted all the points for an operating refrigeration system on a pressure-enthalpy (PE) chart. Which item below would you not do next?

Explanation

Creating a database system to track all readings would not be the next step because the question asks what you would NOT do next. The previous options involve comparing the data with the manufacturer, experimenting with changing values, and filing the data for future reference. Therefore, creating a database system is not the next logical step in this scenario.

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102. The safety devices used on air compressors should be checked

Explanation

The safety devices used on air compressors should be checked annually to ensure their proper functioning and to prevent any potential hazards or accidents. Regular inspections and maintenance help identify any issues or wear and tear that may have occurred over time. By checking the safety devices annually, operators can address any necessary repairs or replacements, ensuring the continued safety and efficiency of the air compressor system.

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103. Normally the temperature of the water entering the condenser on a centrifugal air-condition system should be about

Explanation

The temperature of the water entering the condenser on a centrifugal air-conditioning system should be around 85°F. This temperature is ideal for the condenser to effectively remove heat from the refrigerant and cool it down. If the water temperature is too low, it may not provide enough cooling capacity, while if it is too high, it may not effectively remove heat from the refrigerant. Therefore, 85°F is the optimal temperature for efficient cooling in a centrifugal air-conditioning system.

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104.  R–401A and B can be described as a/an

Explanation

R-401A and B are described as hydrofluorocarbon (HFC)-based alternatives. This means that they are alternatives that use HFCs as their primary components. HFCs are a type of synthetic refrigerant that does not contain chlorine, making them less harmful to the ozone layer compared to chlorofluorocarbons (CFCs). HFC-based alternatives are commonly used in refrigeration and air conditioning systems as a more environmentally friendly option.

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105. How many air-compressor starts per hour would require a constant speed control?

Explanation

The question is asking for the number of air-compressor starts per hour that would require a constant speed control. A constant speed control is typically used when there is a need for a consistent and steady speed. In the context of air compressors, it is likely that a constant speed control would be required when there is a high demand for compressed air. Out of the given options, 13 starts per hour would indicate a relatively high demand and would therefore require a constant speed control.

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106. Which item does not indicate the cylinders are unloading when you are adjusting a hydraulic unloader mechanism?

Explanation

When adjusting a hydraulic unloader mechanism, the cylinders should indicate that they are unloading. This means that the pressure inside the cylinders should decrease, which would cause the amperage to drop, the suction pressure to rise, and the sound of the compressor to change. However, the oil pressure should not excessively fluctuate during this process. Therefore, the item that does not indicate the cylinders are unloading is "The oil pressure will excessively fluctuate."

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107. Which display-cabinet defrost method is limited to operating temperatures above 28 degrees?

Explanation

The compressor off-time defrost method is limited to operating temperatures above 28 degrees because it relies on turning off the compressor to allow the accumulated ice to melt. This method is not effective at lower temperatures because the compressor needs to be running to maintain the desired temperature inside the display cabinet. Therefore, it is only suitable for defrosting at higher temperatures where turning off the compressor for a period of time will not cause the temperature to drop too much.

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108. A good refrigerant oil will have

Explanation

not-available-via-ai

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109. Where is the subcooler installed on a compound system?

Explanation

The subcooler is installed in the liquid line before the evaporator. This placement allows the subcooler to cool down the refrigerant even further before it enters the evaporator. By removing additional heat from the refrigerant, the subcooler helps to increase the system's overall efficiency and improve the cooling capacity.

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110. When solenoid valves are used in the suction line of a multi-evaporator system, what accessory must be installed?

Explanation

When solenoid valves are used in the suction line of a multi-evaporator system, an accumulator must be installed. An accumulator is a device that is used to store excess refrigerant and oil from the evaporator during periods of low load or low refrigerant flow. It helps to prevent liquid refrigerant from entering the compressor, which can cause damage. By installing an accumulator, it ensures that only vapor refrigerant is delivered to the compressor, improving the overall efficiency and performance of the system.

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111. During defrost, the heat pump system does not

Explanation

During defrost, the heat pump system does not keep temperatures constant. This is because defrosting involves melting any ice or frost that has accumulated on the outdoor unit. To do this, the system temporarily switches to a heating cycle, where the outdoor fan is turned off and electric heat may be used to warm the outdoor unit and melt the ice. As a result, the system cannot maintain constant temperatures during defrost.

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112. The purge unit on a centrifugal machine is not designed to

Explanation

The purge unit on a centrifugal machine is specifically designed to remove contaminated oil. It is not intended to remove air, water, or recover refrigerant. Its main function is to eliminate oil that has been contaminated with impurities or particles, ensuring the efficiency and proper functioning of the centrifugal machine.

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113. What type of alternative is refrigerant R–402A?

Explanation

Refrigerant R-402A is classified as a ternary blend. A ternary blend refers to a mixture that consists of three different components. In the case of R-402A, it is composed of three refrigerants - R-125, R-134a, and R-600a. This combination of refrigerants provides specific properties and performance characteristics suitable for certain cooling applications.

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114.  In a heat exchanger, the heat that is transferred comes from the

Explanation

In a heat exchanger, the heat that is transferred comes from the liquid line. The liquid line carries the condensed refrigerant from the condenser to the expansion valve. As the high-pressure liquid refrigerant flows through the liquid line, it releases heat to the surrounding environment, which allows it to change from a high-pressure liquid to a low-pressure liquid-vapor mixture. This heat transfer process is essential for cooling down the refrigerant and preparing it for the next stage of the refrigeration cycle.

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115. Which type of ice-machine evaporator operates underwater?

Explanation

The correct answer is "Cell type" because cell type evaporators are designed to operate underwater. These evaporators consist of individual cells or compartments that are submerged in water, allowing for efficient heat transfer and ice production. This design is commonly used in commercial ice machines to produce large quantities of ice quickly. Tube type evaporators, on the other hand, operate above water and use a series of tubes to circulate refrigerant and extract heat. Vertical plate and horizontal plate evaporators are also not designed to operate underwater.

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116. Which type of cooler is generally used in the common water cooler?

Explanation

The correct answer is Shell-and-coil. In a common water cooler, a shell-and-coil type of cooler is generally used. This type of cooler consists of a coil of tubing placed inside a shell. The water flows through the coil while the cooling medium, such as refrigerant or chilled water, circulates around the coil in the shell. This design allows for efficient heat transfer between the water and the cooling medium, resulting in the cooling of the water in the cooler.

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117. The connecting point of a cascade system is

Explanation

The connecting point of a cascade system is a condenser-evaporator. In a cascade system, two refrigeration cycles are used, with one cycle operating at a higher temperature and the other at a lower temperature. The condenser-evaporator acts as the connection point between the two cycles, allowing the transfer of heat from the higher temperature cycle to the lower temperature cycle. This allows for efficient cooling at multiple temperature levels in applications such as industrial refrigeration or cryogenic cooling.

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118. How is the latent heat line shown on the pressure-enthalpy (PE) chart?

Explanation

The latent heat line is shown as horizontal on the pressure-enthalpy (PE) chart. This means that during a phase change, such as vaporization or condensation, the enthalpy remains constant while the pressure changes. This indicates that the heat transfer is occurring at a constant temperature, as the enthalpy is a measure of the heat content of a substance.

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119. Which pressure control is designed to operate from a pressure differential of the system?

Explanation

The oil-pressure safety control is designed to operate from a pressure differential of the system. This means that it is specifically designed to monitor and control the oil pressure in a system, ensuring that it stays within safe limits. It is likely used in systems where maintaining proper oil pressure is crucial for the safe and efficient operation of equipment or machinery.

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120. On what basis should you check and clean the air filters used on air compressors?

Explanation

Air filters used on air compressors should be checked and cleaned on a weekly basis to ensure optimal performance and prevent any potential damage to the compressor. Regular maintenance of the air filters helps to remove dust, debris, and other contaminants from the air, allowing for clean and efficient air flow. By checking and cleaning the filters weekly, any build-up of dirt or clogs can be identified and resolved promptly, ensuring that the compressor operates effectively and prolonging its lifespan.

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121. What can be used in place of thermostats and solenoid valves to control the temperatures in a multiple-temperature, multiple-evaporator system?

Explanation

Evaporator pressure regulating valves can be used in place of thermostats and solenoid valves to control the temperatures in a multiple-temperature, multiple-evaporator system. These valves regulate the pressure in the evaporator, which in turn controls the temperature. By adjusting the pressure, the evaporator pressure regulating valves can effectively control the temperature without the need for separate thermostats and solenoid valves. This provides a more efficient and streamlined method of temperature control in such systems.

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122. Air compressors with operating pressures above 200 pounds per square inch gauge (psig) are required to have a hydrostatic test

Explanation

Air compressors with operating pressures above 200 pounds per square inch gauge (psig) are required to have a hydrostatic test every three years. This means that the compressors need to undergo a pressure test to ensure their safety and reliability. By conducting the test every three years, any potential issues or weaknesses in the compressor can be identified and addressed, reducing the risk of accidents or malfunctions. Regular testing also helps to maintain the efficiency and performance of the compressors, ensuring they continue to operate effectively.

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123. What can be used to control a single-temperature, multiple-evaporator system?

Explanation

A low-pressure motor control can be used to control a single-temperature, multiple-evaporator system. This control regulates the motor speed based on the low-pressure conditions in the system, ensuring that the evaporators are operating at the desired temperature. By adjusting the motor speed, the control can effectively manage the cooling capacity of the system and maintain the desired temperature in each evaporator. This allows for efficient and precise control of the system, ensuring optimal performance and temperature control.

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124. Air-compressor receiver tanks should be inspected

Explanation

Air-compressor receiver tanks should be inspected every two years. This frequency allows for regular monitoring of the tank's condition and ensures that any potential issues or defects are identified and addressed in a timely manner. Inspections help to prevent safety hazards, such as leaks or structural failures, and ensure the efficient operation of the air compressor system. By conducting inspections every two years, maintenance and repair activities can be planned and implemented effectively, reducing the risk of unexpected breakdowns and costly downtime.

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 Refrigerants containing chlorine are said to destroy
What must you do to the power before you perform a preoperational...
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What term refers to how hot or cold a substance is?
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The best criteria to follow when you are inspecting equipment are
All moving parts on an air compressor should have
What is the term for a refrigeration unit to operate or cycle on?
 The float assembly in an oil separator is activated by the
Which of these refrigerants has an ozone depletion rating of zero?
What must be balanced to distribute the load as equally as possible...
Two different metals that are bonded into a strip or coil are called
You are retrofitting a system that does not have a receiver. To do the...
 To create the required pressure drop, the capillary tube uses a...
Where do you install a sight glass and/or moisture indicator in a...
The disadvantage of water-cooled condensers is
What device is used to prevent liquid refrigerant from entering the...
Which heat pump component prevents liquid refrigerant from entering...
The direct-expansion evaporator picks up or absorbs heat directly from...
What type of heat when added to a substance causes a measured...
How much of the refrigerant charge should a receiver hold?
What is a big problem with humidity control equipment?
On a centrifugal machine, the refrigerant flows from the first-stage...
On systems that contain over how many pounds of refrigerant is passive...
 The advantage of an air-cooled condenser is
Which pressure control has contacts that open on a rise in pressure?
Which component is installed at the inlet of the evaporator?
What triggers a refrigeration unit to cycle on or off?
Temperature glide in an zeotropic refrigerant means that the...
What is the maximum fine and jail sentence that service technicians...
Heat that is picked up in the refrigeration system is rejected at the
Which processes take place inside the condenser?
Which packaged unit normally uses only one fan motor?
Which type of water-cooled condenser has removable heads that allow...
What is the line to inlet relationship of refrigerant vapor travel as...
In a multi stage air-compressor installation, what is used to remove...
Complete vaporization in an evaporator occurs at point
Which alternative replacement for R–502 is a patented azeotrope?
How does the rotary compressor compress the refrigerant vapor?
What program is designed to keep heating, ventilation,...
Where are the coldest rooms located in a permanent cold-storage plant?
During retrofitting, which component might have to be reset to...
An ice-cream cabinet is similar to a
 Cleaning a refrigerant at the job site or at a local service...
 When polyolester oil is used in place of mineral oil during a...
 Which organization requires that a comprehensive risk assessment...
Proportionately which refrigerator has the biggest freezer...
The Environmental Protection Agency (EPA) has developed a Significant...
The thermostatic expansion valve maintains a fully active evaporator...
How is the capillary tube in a system affected by the refrigerant...
What do filter-driers not remove from a refrigeration system?
In which two parts of a refrigeration system does a pressure change...
The reciprocating refrigeration compressor is designed to remove
What type of thermostatic expansion valve has a charged sensing bulb...
In which major component does absorbed heat cause liquid refrigerant...
What prevents direct impact of refrigerant vapors on the tubing bundle...
What is the maximum percent a refillable cylinder can be refilled with...
What type of rotary compressor has the blade set into the cylinder?
Which compressor type is used with refrigerants that have a large gas...
Which evaporator type is designed to maintain an even temperature...
 Which refrigerant oil is designed for use with the new ternary...
To help ensure that the proper refrigerant and lubricant will be used...
Which desiccant is the most popular and can be left in the system...
During equipment cooling, humidity cannot be added to the air by
In relation to the curve, where is the liquid refrigerant shown on the...
On a multi-evaporator system, the evaporator pressure regulating (EPR)...
Which type piston can suction gas pass through?
Air intake filters used on air compressors are designed to prevent
What is it called when two or more compressors are piped in series to...
Which type of ice-machine evaporator produces a slab of ice that is...
In relation to the curve, where does the refrigerant change of state...
Where does the compressed refrigerant vapor go during the heating...
Which cooler is used exclusively to cool liquids?
What condition must exist before using a pressure-temperature (PT)...
The receiver tanks used on air compressors are designed to be
On Type II systems, what level of evacuation in the isolated component...
R–401A is not a suitable alternative refrigerant for
What factor is not part of the known factors for using a...
You are retrofitting a system with an alternative refrigerant and you...
When manual condensate drains are installed on an air receiver tank,...
You have plotted all the points for an operating refrigeration system...
Commercial and industrial systems with leaks exceeding what percent...
What accessory is added to the cascade system to increase its...
The economizer on a centrifugal machine prevents liquid refrigerant...
What type maintenance action do you perform on operating heating,...
Which type of compressor uses an orbiting motion for compression?
The ultralow-temperature classification begins at
The hydraulic cylinder unloader mechanism is designed to unload the...
When conducting an operational check of the mechanical part of a...
Which display-cabinet defrosting method has the advantage of not being...
Which item is not an advantage of a multiple-compressor system?
When the compressor air intake is piped to the outside, it should be
A retrofitted air-conditioning system still has the original capillary...
Which pressure control is designed to cut in on a rise in pressure and...
To regulate the load on a water-cooled condenser, you should
What type of thermostatic expansion valve has a bulb that is charged...
Which of these refrigerants is colorless and has a very pronounced...
Approximately what percent of the evaporator tubing bundle is covered...
R-406a can be used to replace
You have plotted all the points for an operating refrigeration system...
The safety devices used on air compressors should be checked
Normally the temperature of the water entering the condenser on a...
 R–401A and B can be described as a/an
How many air-compressor starts per hour would require a constant speed...
Which item does not indicate the cylinders are unloading when you are...
Which display-cabinet defrost method is limited to operating...
A good refrigerant oil will have
Where is the subcooler installed on a compound system?
When solenoid valves are used in the suction line of a...
During defrost, the heat pump system does not
The purge unit on a centrifugal machine is not designed to
What type of alternative is refrigerant R–402A?
 In a heat exchanger, the heat that is transferred comes from the
Which type of ice-machine evaporator operates underwater?
Which type of cooler is generally used in the common water cooler?
The connecting point of a cascade system is
How is the latent heat line shown on the pressure-enthalpy (PE) chart?
Which pressure control is designed to operate from a pressure...
On what basis should you check and clean the air filters used on air...
What can be used in place of thermostats and solenoid valves to...
Air compressors with operating pressures above 200 pounds per square...
What can be used to control a single-temperature, multiple-evaporator...
Air-compressor receiver tanks should be inspected
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