AC 432 Refrigeration Systems

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Quizzes Created: 4 | Total Attempts: 3,061

Questions: 68 | Attempts: 830 | Updated: Mar 21, 2023

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Refrigeration is used in different appliances around us, most commonly in refrigerators in our houses and places of work. How conversant are you with the refrigeration system, functionality and how to repair broken parts? Give this test on the system a try and polish up what you have forgotten before the finals.

Questions and Answers

1.

The capacity of an evaporator is affected by ____.
- A.
  
  The saturation pressure of the low side of the system
- B.
  
  The saturation pressure of the high side of the system
- C.
  
  The amount of evaporator superheat
- D.
  
  All of the above
Correct Answer
D. All of the above

Explanation
The capacity of an evaporator is affected by all of the above factors. The saturation pressure of the low side of the system determines the temperature at which the refrigerant evaporates, thus affecting the heat transfer process. Similarly, the saturation pressure of the high side of the system affects the condensing temperature and the overall efficiency of the system. Additionally, the amount of evaporator superheat, which is the temperature rise above the refrigerant's saturation temperature, also impacts the evaporator's capacity as it affects the heat transfer rate. Therefore, all of these factors play a role in determining the capacity of an evaporator.

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2.

A forced draft medium temperature evaporator would ____.
- A.
  
  Be defrosted by off-cycle defrost
- B.
  
  Not need to be defrosted
- C.
  
  Need electric defrost
- D.
  
  Need a hot gas defrost
Correct Answer
A. Be defrosted by off-cycle defrost

Explanation
A forced draft medium temperature evaporator would be defrosted by off-cycle defrost. Off-cycle defrost is a method of defrosting where the refrigeration system is temporarily shut down, allowing the accumulated ice on the evaporator to melt off naturally. In a forced draft evaporator, air is forced across the evaporator coils by a fan, which helps to enhance the heat transfer process. This forced air movement helps to prevent ice buildup on the coils. However, if any ice does accumulate, it can be easily melted off using off-cycle defrost, without the need for additional heating elements or a hot gas defrost system.

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3.

A forced draft high temperature evaporator would ____.
- A.
  
  Have its fins very close together
- B.
  
  Not need to be defrosted
- C.
  
  Need a hot gas defrost
- D.
  
  Both a and b
Correct Answer
D. Both a and b

Explanation
A forced draft high temperature evaporator would have its fins very close together and not need to be defrosted. This is because the close proximity of the fins allows for efficient heat transfer, preventing the formation of ice and frost. Additionally, the forced draft design ensures a continuous flow of air, further preventing the need for defrosting. Therefore, both options a and b are correct.

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4.

During the defrost cycle of a forced draft low temperature evaporator, the evaporator fan would ____.
- A.
  
  Remain on to speed up the defrost
- B.
  
  Turn off
- C.
  
  Cycle with the condenser
- D.
  
  Cycle with the compressor
Correct Answer
B. Turn off

Explanation
During the defrost cycle of a forced draft low temperature evaporator, the evaporator fan would turn off. This is because during the defrost cycle, the heat from the defrost heaters is used to melt the ice that has accumulated on the evaporator coils. If the evaporator fan remains on, it would blow the warm air away from the coils, reducing the effectiveness of the defrosting process. Therefore, turning off the fan allows the heat to be concentrated on the coils, speeding up the defrosting process.

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5.

If an evaporator has a pressure drop of 10 psig and the low side pressure is 15 psig, what is the pressure at the inlet of the evaporator?
- A.
  
  10 psig
- B.
  
  25 psig
- C.
  
  15 psig
- D.
  
  5 psig
Correct Answer
B. 25 psig

Explanation
The pressure at the inlet of the evaporator is 25 psig because the pressure drop is subtracted from the low side pressure. In this case, the pressure drop is 10 psig, so when it is subtracted from the low side pressure of 15 psig, the result is 25 psig.

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6.

Excess evaporator superheat ____.
- A.
  
  Is desired to prevent liquid from entering the compressor
- B.
  
  Will reduce the cooling capacity of the system
- C.
  
  Can be removed by removing refrigerant from the system
- D.
  
  Will cause the system to go into defrost
Correct Answer
B. Will reduce the cooling capacity of the system

Explanation
Excess evaporator superheat refers to the temperature difference between the refrigerant entering the evaporator and its saturation temperature. When there is too much superheat, it means that the refrigerant is not fully evaporated before entering the compressor. This can lead to a decrease in the cooling capacity of the system because the compressor is designed to compress vapor, not liquid. Therefore, the correct answer is that excess evaporator superheat will reduce the cooling capacity of the system.

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7.

If a low temperature evaporator is forming excess ice, which of the following could be a possible problem?
- A.
  
  The evaporator fan motor is defective.
- B.
  
  The unit is not staying in defrost long enough.
- C.
  
  The defrost heater is defective.
- D.
  
  All of the above are correct.
Correct Answer
D. All of the above are correct.

Explanation
If a low temperature evaporator is forming excess ice, all of the given options could be possible problems. A defective evaporator fan motor can cause insufficient air circulation, leading to ice formation. If the unit is not staying in defrost long enough, the ice on the evaporator may not melt completely, resulting in excess ice buildup. A defective defrost heater can also prevent proper melting of ice during the defrost cycle, leading to excess ice formation. Therefore, all of the mentioned issues could contribute to the formation of excess ice on the low temperature evaporator.

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8.

If a high temperature evaporator is forming ice, which of the following is a possible problem?
- A.
  
  Evaporator fan not running
- B.
  
  Compressor not running
- C.
  
  Condenser fan not running
- D.
  
  No problem, ice formation normal
Correct Answer
A. Evaporator fan not running

Explanation
If a high temperature evaporator is forming ice, a possible problem could be that the evaporator fan is not running. The evaporator fan is responsible for circulating air over the evaporator coil, which helps to remove heat and prevent ice formation. If the fan is not running, the air flow will be restricted, causing the evaporator coil to become too cold and resulting in ice formation.

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9.

If a low temperature evaporator is forming ice, which of the following is a possible problem?
- A.
  
  Evaporator fan not running
- B.
  
  Compressor not running
- C.
  
  Condenser fan not running
- D.
  
  No problem, ice formation normal
Correct Answer
D. No problem, ice formation normal
10.

If an R-12 refrigeration system is operating with a 25.4 psig suction pressure, what is the evaporator superheat if the evaporator outlet temperature is 34°F?
- A.
  
  9°F
- B.
  
  59°F
- C.
  
  34°F
- D.
  
  25°F
Correct Answer
A. 9°F

Explanation
The evaporator superheat is the difference between the actual evaporator outlet temperature and the saturation temperature at the corresponding evaporator pressure. In this case, the evaporator outlet temperature is given as 34°F and the suction pressure is given as 25.4 psig. By looking up the saturation temperature of R-12 at 25.4 psig, we can find that it is 25°F. Therefore, the evaporator superheat is 34°F - 25°F = 9°F.

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11.

A typical evaporator operating temperature in an air-conditioning system is ____.
- A.
  
  40°F
- B.
  
  55°F
- C.
  
  75°F
- D.
  
  200°F
Correct Answer
A. 40°F

Explanation
A typical evaporator operating temperature in an air-conditioning system is 40°F because this temperature allows for efficient cooling of the air. At this temperature, the evaporator coil can effectively absorb heat from the surrounding air, causing the refrigerant to evaporate and cool the air passing through the system. This temperature is also suitable for maintaining a comfortable indoor environment without causing excessive cooling or freezing of the air.

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12.

A large capacity evaporator would probably have ____.
- A.
  
  Stainless steel tubing
- B.
  
  An excess of liquid refrigerant
- C.
  
  An excess of vapor refrigerant
- D.
  
  Multiple refrigerant circuits
Correct Answer
D. Multiple refrigerant circuits

Explanation
A large capacity evaporator would probably have multiple refrigerant circuits. This is because a larger evaporator requires more refrigerant to be evaporated in order to cool a larger space or handle a higher cooling load. Having multiple refrigerant circuits allows for better distribution of the refrigerant and helps to ensure efficient and effective cooling throughout the evaporator.

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13.

If the application requires a coil design to operate below 32°F, there must be provision for ____.
- A.
  
  Flooding the evaporator
- B.
  
  Adding the evaporator
- C.
  
  Defrost
- D.
  
  Suction pressure control
Correct Answer
C. Defrost

Explanation
If the application requires a coil design to operate below 32°F, there must be provision for defrost. This is because when operating at such low temperatures, ice can build up on the evaporator coil, reducing its efficiency and potentially causing damage. Defrosting is necessary to remove the ice buildup and ensure proper functioning of the coil.

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14.

The heat required for off-cycle defrost is obtained from ____.
- A.
  
  Supplemental electric heat when the system is shut down
- B.
  
  Hot gas when the system is operating
- C.
  
  The space temperature when the compressor is off
- D.
  
  The space temperature when the compressor is off
Correct Answer
C. The space temperature when the compressor is off

Explanation
The heat required for off-cycle defrost is obtained from the space temperature when the compressor is off. During off-cycle defrost, the compressor is not running, so there is no heat generated by the system. Instead, the heat needed for defrosting is taken from the surrounding air or space temperature. This heat is used to melt any ice or frost that has accumulated on the evaporator coil, allowing the system to operate efficiently once the compressor starts again.

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15.

A direct expansion-type evaporator is also called a ____.
- A.
  
  Flooded evaporator
- B.
  
  Dry-type evaporator
- C.
  
  Multi-circuit evaporator
- D.
  
  Stamped evaporator
Correct Answer
B. Dry-type evaporator

Explanation
A direct expansion-type evaporator is also called a dry-type evaporator because it operates by directly expanding the refrigerant inside the evaporator coils. This type of evaporator does not use a liquid refrigerant, hence the term "dry-type". Instead, the refrigerant evaporates directly from a gaseous state to a vapor state in the coils, absorbing heat from the surrounding air or liquid in the process. This design allows for efficient heat transfer and is commonly used in air conditioning systems and refrigeration units.

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16.

A refrigeration system designed for the storage of flowers or candy is considered a ____ type.
- A.
  
  High temperature
- B.
  
  Medium temperature
- C.
  
  Low temperature
- D.
  
  Sharp freezing
Correct Answer
A. High temperature

Explanation
A refrigeration system designed for the storage of flowers or candy is considered a high temperature type because it is not meant to freeze or cool the items to extremely low temperatures. Instead, it is designed to maintain a slightly cooler temperature than the surrounding environment to prevent spoilage or melting, but not cold enough to freeze the products.

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17.

A typical superheat for an evaporator operating under normal conditions would be ____.
- A.
  
  14 to 16°F
- B.
  
  4 to 6°F
- C.
  
  8 to 12°F
- D.
  
  6 to 8°F
Correct Answer
C. 8 to 12°F

Explanation
A typical superheat for an evaporator operating under normal conditions would be 8 to 12°F. Superheat is the temperature difference between the actual temperature of the refrigerant vapor and its saturation temperature at a given pressure. It is important to have a certain amount of superheat in the evaporator to ensure that the refrigerant is fully vaporized before it leaves the evaporator. A superheat of 8 to 12°F is considered normal and allows for efficient heat transfer and prevents liquid refrigerant from entering the compressor.

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18.

When a system with a water-cooled condenser cycles off, the water regulating valve should ____.
- A.
  
  Remain open during the off cycle
- B.
  
  Close, since the head pressure is lower
- C.
  
  Open all the way to remove any residual heat
- D.
  
  Re-calibrate itself to maintain the new lower head pressure
Correct Answer
B. Close, since the head pressure is lower

Explanation
When a system with a water-cooled condenser cycles off, the head pressure is lower because the compressor is not running and there is no heat being generated. Therefore, the water regulating valve should close to prevent unnecessary water flow and conserve energy.

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19.

A normally operating water-cooled condenser is operating with a 10° differential between water in and water out. If the amount of 85°F water going through the condenser is reduced, which of the following is a possible temperature of the water leaving the condenser?
- A.
  
  75°F
- B.
  
  0°F
- C.
  
  95°F
- D.
  
  105°F
Correct Answer
D. 105°F

Explanation
If the amount of 85°F water going through the condenser is reduced, it means that less heat is being transferred from the condenser to the water. As a result, the temperature of the water leaving the condenser would increase. Therefore, a possible temperature of the water leaving the condenser could be 105°F.

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20.

A normally operating water-cooled condenser is operating with a 10° differential between water in and water out. If scale forms on the water tubes and the entering water is 85°F, which of the following is possible?
- A.
  
  The outlet water will be 88°F.
- B.
  
  The system head pressure will rise
- C.
  
  The water regulating valve will close.
- D.
  
  Both a and b are correct.
Correct Answer
D. Both a and b are correct.

Explanation
Both options a and b are correct because when scale forms on the water tubes, it acts as an insulating layer, reducing the heat transfer efficiency. As a result, the outlet water temperature will increase, causing the outlet water to be 88°F instead of the usual 85°F. Additionally, the reduced heat transfer efficiency will cause the system head pressure to rise as the condenser struggles to remove heat effectively. Therefore, both a and b are possible outcomes in this scenario.

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21.

Which of the following would allow a system to operate more efficiently?
- A.
  
  Condenser that had refrigerant leaving with 10°F of superheat
- B.
  
  Condenser that had refrigerant leaving with 15° of subcooling
- C.
  
  Condenser that had refrigerant leaving as 100% vapor
- D.
  
  Condenser that had refrigerant leaving with 10° of subcooling
Correct Answer
B. Condenser that had refrigerant leaving with 15° of subcooling

Explanation
A condenser that has refrigerant leaving with 15° of subcooling would allow a system to operate more efficiently. Subcooling refers to the cooling of a liquid refrigerant below its saturation temperature. By having the refrigerant leave the condenser with 15° of subcooling, it means that the refrigerant is being cooled further, which increases its density. This increased density allows for better heat transfer in the evaporator, resulting in improved system efficiency.

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22.

If an R-12 refrigeration system has its air-cooled condensing unit on a 100°F roof and the condenser outlet temperature (refrigerant) is 115°F, with how much subcooling is the condenser operating?
- A.
  
  30°F
- B.
  
  15°F
- C.
  
  100°F
- D.
  
  130°F
Correct Answer
B. 15°F

Explanation
The condenser is operating with 15°F of subcooling. Subcooling is the temperature difference between the liquid refrigerant leaving the condenser and its saturation temperature. In this case, the condenser outlet temperature is 115°F, which is 15°F higher than the saturation temperature. Therefore, the condenser is operating with 15°F of subcooling.

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23.

Which of the following condensers is the most efficient?
- A.
  
  Forced draft air-cooled
- B.
  
  Induced draft air-cooled
- C.
  
  Water-cooled parallel flow
- D.
  
  Water-cooled counter flow
Correct Answer
D. Water-cooled counter flow

Explanation
Water-cooled counter flow condensers are the most efficient because they allow for maximum heat transfer between the refrigerant and the cooling water. In a counter flow configuration, the refrigerant and the cooling water flow in opposite directions, which creates a large temperature difference between them. This temperature difference enhances the heat transfer process, resulting in higher efficiency compared to other condenser types. Additionally, water-cooled condensers generally have a higher heat transfer coefficient than air-cooled condensers, further contributing to their superior efficiency.

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24.

An air-cooled condenser that is operating in a climate that has four distinct seasons must ____.
- A.
  
  Have some type of head pressure control
- B.
  
  Use a water regulating valve
- C.
  
  Have a multi-circuit evaporator
- D.
  
  Operate with zero degrees of subcooling
Correct Answer
A. Have some type of head pressure control

Explanation
An air-cooled condenser that is operating in a climate that has four distinct seasons must have some type of head pressure control because the temperature and humidity levels can vary greatly throughout the year. Head pressure control helps to maintain the condenser's operating pressure within a desired range, ensuring efficient heat transfer and preventing the condenser from becoming overworked or damaged. By adjusting the head pressure, the condenser can effectively cool the refrigerant and maintain optimal performance regardless of the changing outdoor conditions.

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25.

What can be used to maintain the head pressure of a system with a water-cooled condenser?
- A.
  
  Fan cycling
- B.
  
  Dampers or louvers
- C.
  
  Water regulating valve
- D.
  
  All of the above
Correct Answer
C. Water regulating valve

Explanation
A water regulating valve can be used to maintain the head pressure of a system with a water-cooled condenser. This valve allows for precise control of the water flow rate to the condenser, which in turn helps regulate the condenser's temperature and pressure. By adjusting the water flow, the valve ensures that the head pressure remains at the desired level, optimizing the system's performance and efficiency. Fan cycling and dampers or louvers may also be used in conjunction with the water regulating valve to further control the head pressure, but they are not the only options and may not be necessary in all cases.

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26.

Which of the following can be used to maintain the head pressure of a system with an air-cooled condenser?
- A.
  
  Fan cycling
- B.
  
  Condenser flooding valve
- C.
  
  Dampers or louvers
- D.
  
  All of the above
Correct Answer
D. All of the above

Explanation
All of the options mentioned can be used to maintain the head pressure of a system with an air-cooled condenser. Fan cycling helps to control the speed of the condenser fan, thereby regulating the head pressure. The condenser flooding valve adjusts the flow of refrigerant to the condenser, which also affects the head pressure. Dampers or louvers can be adjusted to control the airflow through the condenser, thus influencing the head pressure. Therefore, all of these options can be utilized to maintain the head pressure of a system with an air-cooled condenser.

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27.

The refrigerant in a condenser in a refrigeration system ____.
- A.
  
  Absorbs heat
- B.
  
  Gives up heat
- C.
  
  Changes to a vapor
- D.
  
  Is under lower pressure than the evaporator
Correct Answer
B. Gives up heat

Explanation
In a refrigeration system, the condenser is responsible for releasing heat from the refrigerant. As the refrigerant flows through the condenser, it undergoes a phase change from a high-pressure vapor to a high-pressure liquid. During this process, the refrigerant gives up heat to the surroundings, which allows it to cool down and condense. Therefore, the correct answer is "gives up heat."

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28.

The condenser in a refrigeration system ____.
- A.
  
  Desuperheats the vapor from the compressor
- B.
  
  Condenses the vapor from the compressor
- C.
  
  Subcools the liquid refrigerant before it leaves the condenser
- D.
  
  All of the above
Correct Answer
D. All of the above

Explanation
The condenser in a refrigeration system performs multiple functions. Firstly, it desuperheats the vapor from the compressor, removing excess heat and reducing the temperature. Secondly, it condenses the vapor, converting it back into a liquid state. Lastly, it subcools the liquid refrigerant before it leaves the condenser, further lowering its temperature. Therefore, the correct answer is "all of the above" as the condenser performs all these tasks in a refrigeration system.

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29.

Mineral deposits in the water portion of a water-cooled condenser act as ____.
- A.
  
  A conductor of heat
- B.
  
  An insulator
- C.
  
  A cleaning solution
- D.
  
  They have no effect on the operation of the condenser.
Correct Answer
B. An insulator

Explanation
Mineral deposits in the water portion of a water-cooled condenser act as an insulator. This means that they hinder the transfer of heat between the water and the condenser. Insulators are substances that do not conduct heat well, so when mineral deposits build up in the condenser, they create a barrier that prevents efficient heat transfer. As a result, the condenser may become less effective in cooling the water, leading to decreased efficiency and potential operational issues.

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30.

The water circuit in shell and coil and coil-type tube-in-a-tube condensers must be cleaned ____.
- A.
  
  By removing the end caps
- B.
  
  With a brush
- C.
  
  Chemically
- D.
  
  By air pressure
Correct Answer
C. Chemically

Explanation
The water circuit in shell and coil and coil-type tube-in-a-tube condensers must be cleaned chemically. This is because chemical cleaning is the most effective method to remove any buildup or deposits that may accumulate in the water circuit. Chemical cleaners are specifically designed to dissolve and remove scale, rust, and other contaminants, ensuring optimal performance and efficiency of the condenser.

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31.

The shell and tube condenser is cleaned ____.
- A.
  
  With a brush after removing the end caps
- B.
  
  Only with chemicals
- C.
  
  With compressed air
- D.
  
  With a vacuum cleaner
Correct Answer
A. With a brush after removing the end caps

Explanation
The shell and tube condenser is cleaned with a brush after removing the end caps. This is because the brush allows for effective scrubbing and removal of any debris or buildup inside the condenser tubes. Removing the end caps provides access to the tubes, making it easier to clean them thoroughly. Using a brush ensures a physical cleaning action, which can be more effective than solely relying on chemicals, compressed air, or a vacuum cleaner.

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32.

If the waterflow is reduced, the temperature difference across a condenser will ____.
- A.
  
  Increase
- B.
  
  Decrease
- C.
  
  Remain the same
- D.
  
  Correspond to the evaporator saturation temperature
Correct Answer
A. Increase

Explanation
When the waterflow is reduced in a condenser, it means that there is less water available to remove heat from the condenser. This leads to a decrease in the overall heat transfer rate, resulting in a higher temperature difference across the condenser. Therefore, the temperature difference across the condenser will increase when the waterflow is reduced.

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0
33.

In a water-cooled condenser, a regulating valve is used to control the ____.
- A.
  
  Refrigerant flow through the pressure reducing device
- B.
  
  Refrigerant condensing temperature
- C.
  
  Suction pressure
- D.
  
  Water temperature
Correct Answer
B. Refrigerant condensing temperature

Explanation
In a water-cooled condenser, a regulating valve is used to control the refrigerant condensing temperature. This valve adjusts the flow of water through the condenser, which in turn affects the temperature at which the refrigerant condenses. By regulating the condensing temperature, the system can maintain optimal operating conditions and improve overall efficiency.

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34.

Control of the head pressure in an air-cooled condenser is done by ____.
- A.
  
  Cycling the condenser fan
- B.
  
  Controlling dampers in the airstream through the condenser
- C.
  
  Flooding the condenser with refrigerant
- D.
  
  All of the above
Correct Answer
D. All of the above

Explanation
The control of head pressure in an air-cooled condenser can be achieved through multiple methods. One way is by cycling the condenser fan, which adjusts the air flow and helps regulate the condenser temperature. Another method is by controlling dampers in the airstream through the condenser, which allows for better control of the air flow and heat transfer. Lastly, flooding the condenser with refrigerant can also help in controlling the head pressure. Therefore, all of the above options are correct ways to control the head pressure in an air-cooled condenser.

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35.

In a water-cooled condenser with dirty condenser tubes, the temperature difference between the refrigerant and the leaving water will be ____ when the tubes are clean.
- A.
  
  Less than
- B.
  
  Greater than
- C.
  
  The same as
- D.
  
  Slightly lower than
Correct Answer
B. Greater than

Explanation
When the condenser tubes are dirty, the efficiency of heat transfer between the refrigerant and the water is reduced. This results in a smaller temperature difference between the refrigerant and the leaving water. Therefore, when the tubes are clean, the heat transfer efficiency improves, leading to a larger temperature difference between the refrigerant and the leaving water. Hence, the temperature difference will be greater than when the tubes are dirty.

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36.

Condensing temperatures in an air-cooled condensing unit can be reduced by ____.
- A.
  
  Increasing the condensing surface area
- B.
  
  Increasing the cfm through the condenser
- C.
  
  Decreasing the temperature of the air entering the condenser
- D.
  
  All of the above
Correct Answer
D. All of the above

Explanation
By increasing the condensing surface area, more heat can be dissipated, resulting in lower condensing temperatures. Similarly, increasing the cfm (cubic feet per minute) through the condenser increases the rate of heat transfer, leading to lower temperatures. Additionally, decreasing the temperature of the air entering the condenser provides a cooler environment for heat exchange, further reducing condensing temperatures. Therefore, all of these actions can contribute to reducing the condensing temperatures in an air-cooled condensing unit.

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37.

A stamped plate evaporator usually does not use a fan to move air across it.
- A.
  
  True
- B.
  
  False
Correct Answer
A. True

Explanation
A stamped plate evaporator is designed in such a way that it promotes natural convection for heat transfer. It consists of multiple thin plates with small channels or passages for the refrigerant to flow through. These plates are typically arranged in a stack, allowing for a larger surface area for heat exchange. Due to this design, a fan is not required to move air across the evaporator as the natural convection currents created by the temperature difference between the refrigerant and the surrounding air are sufficient for efficient heat transfer. Therefore, the statement "A stamped plate evaporator usually does not use a fan to move air across it" is true.

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38.

When the velocity of the air moving over an evaporator is slow, the "air film" acts as an insulator and slow the rate of heat exchange.
- A.
  
  True
- B.
  
  False
Correct Answer
A. True

Explanation
When the velocity of the air moving over an evaporator is slow, the "air film" refers to a layer of air that forms on the surface of the evaporator. This air film acts as an insulator, meaning that it inhibits the transfer of heat between the evaporator and the air. As a result, the rate of heat exchange is slowed down. Therefore, the statement is true.

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39.

The refrigerant in the evaporator must be colder than the air passing over it for heat to transfer to the evaporator.
- A.
  
  True
- B.
  
  False
Correct Answer
A. True

Explanation
This statement is true because heat transfer occurs from a higher temperature region to a lower temperature region. In the case of an evaporator, heat is transferred from the air passing over it to the refrigerant. Therefore, the refrigerant in the evaporator must be colder than the air for heat transfer to occur.

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40.

The device used to feed refrigerant to multiple circuits in an evaporator is called a flow circuit.
- A.
  
  True
- B.
  
  False
Correct Answer
B. False

Explanation
The device used to feed refrigerant to multiple circuits in an evaporator is not called a flow circuit. The correct term for this device is a distributor. The distributor evenly distributes the refrigerant to each circuit in the evaporator, ensuring efficient cooling throughout the system.

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41.

Fewer fins per inch on an evaporator allow more ice to build between defrost cycle.
- A.
  
  True
- B.
  
  False
Correct Answer
A. True

Explanation
Fewer fins per inch on an evaporator means that there is more space between the fins for ice to accumulate. This allows for more ice to build up between defrost cycles because there is more surface area available for ice formation. Therefore, the statement is true.

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42.

Every central split cooling system manufactured in the USA today must have a Seasonal Energy Efficiency Ratio (Seer) of at least 10.
- A.
  
  True
- B.
  
  False
Correct Answer
B. False

Explanation
The statement is false because every central split cooling system manufactured in the USA today must have a Seasonal Energy Efficiency Ratio (SEER) of at least 13, not 10. The SEER rating is a measure of the cooling efficiency of the system, and a higher SEER rating indicates greater energy efficiency. Therefore, a SEER rating of 10 would not meet the minimum requirement for central split cooling systems in the USA.

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43.

A water regulating valve helps maintain in a system's head pressure by modulating the flow of refrigerant through the condenser.
- A.
  
  True
- B.
  
  False
Correct Answer
B. False

Explanation
A water regulating valve does not help maintain a system's head pressure by modulating the flow of refrigerant through the condenser. A water regulating valve is used to control the flow of water in a system, typically in a cooling tower or a chilled water system. It does not have any direct impact on the flow of refrigerant or the head pressure in a refrigeration system. Therefore, the statement is false.

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44.

Evaporative condensers operate more efficiently in climates where the wet bulb temperature is a great deal lower than the dry bulb temperature.
- A.
  
  True
- B.
  
  False
Correct Answer
A. True

Explanation
Evaporative condensers operate more efficiently in climates where the wet bulb temperature is significantly lower than the dry bulb temperature because the condenser uses the evaporation of water to cool the refrigerant. When the wet bulb temperature is lower, the water evaporates more easily, resulting in better cooling efficiency. This means that the condenser can effectively remove heat from the refrigerant, allowing the system to function optimally.

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45.

The desired water flow through a condenser connecting to a recirculating water system is 3 gallons per minute.
- A.
  
  True
- B.
  
  False
Correct Answer
A. True

Explanation
The statement is true because it states that the desired water flow through a condenser connecting to a recirculating water system is 3 gallons per minute. This means that the condenser is designed to operate efficiently with a flow rate of 3 gallons per minute, indicating that any other flow rate may not be optimal for the system.

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46.

If a spring pressure of a water regulating valve is increased, the system head pressure will also increase.
- A.
  
  True
- B.
  
  False
Correct Answer
A. True

Explanation
Increasing the spring pressure of a water regulating valve will result in an increase in the force exerted by the valve on the water flowing through it. This increased force will cause the valve to close more tightly, reducing the flow rate and increasing the system head pressure. Therefore, it is true that increasing the spring pressure of a water regulating valve will also increase the system head pressure.

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47.

One large problem designer's face when designing air-cooled refrigeration and air conditioning equipment is a changing ambient from the changing seasons.
- A.
  
  True
- B.
  
  False
Correct Answer
A. True

Explanation
The statement is true because the changing seasons result in varying ambient temperatures, which can pose a challenge for designers of air-cooled refrigeration and air conditioning equipment. As the ambient temperature fluctuates, the equipment needs to be able to adjust and maintain the desired temperature efficiently. Designers must consider these changing conditions to ensure that the equipment functions effectively in different seasons.

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48.

High head pressures from low ambients can cause insufficient refrigerant flow rates through metering devices, which in turn starve evaporators.
- A.
  
  True
- B.
  
  False
Correct Answer
B. False

Explanation
High head pressures from low ambients can indeed cause insufficient refrigerant flow rates through metering devices, leading to inadequate cooling of the evaporators. However, the statement in the question is incorrect as it states the opposite. Therefore, the correct answer is False.

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49.

Low suction pressures, iced coils, short-cycling, and inefficient cooling can also result from low head pressures.
- A.
  
  True
- B.
  
  False
Correct Answer
A. True

Explanation
Low suction pressures, iced coils, short-cycling, and inefficient cooling can indeed result from low head pressures. When the head pressure is low, it means that there is not enough refrigerant being condensed in the condenser. This can lead to a decrease in the suction pressure, causing the coils to ice up and the system to short-cycle. Additionally, the cooling efficiency of the system will be compromised, resulting in inefficient cooling. Therefore, the statement is true.

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50.

Hard starting may also occur in a low ambient conditions causing low head pressures.
- A.
  
  True
- B.
  
  False
Correct Answer
A. True

Explanation
Hard starting refers to difficulties in starting a machine or engine. In low ambient conditions, such as cold weather, the head pressures in the system may be low. This can result in hard starting because the system may not be able to build up the necessary pressure to start properly. Therefore, the statement that hard starting may occur in low ambient conditions causing low head pressures is true.

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Mar 21, 2023

Quiz Edited by
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Feb 18, 2010

Quiz Created by
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AC 432 Refrigeration Systems

The capacity of an evaporator is affected by ____.

A forced draft medium temperature evaporator would ____.

A forced draft high temperature evaporator would ____.

During the defrost cycle of a forced draft low temperature evaporator, the evaporator fan would ____.

If an evaporator has a pressure drop of 10 psig and the low side pressure is 15 psig, what is the pressure at the inlet of the evaporator?

Excess evaporator superheat ____.

If a low temperature evaporator is forming excess ice, which of the following could be a possible problem?

If a high temperature evaporator is forming ice, which of the following is a possible problem?

If a low temperature evaporator is forming ice, which of the following is a possible problem?

If an R-12 refrigeration system is operating with a 25.4 psig suction pressure, what is the evaporator superheat if the evaporator outlet temperature is 34°F?

A typical evaporator operating temperature in an air-conditioning system is ____.

A large capacity evaporator would probably have ____.

If the application requires a coil design to operate below 32°F, there must be provision for ____.

The heat required for off-cycle defrost is obtained from ____.

A direct expansion-type evaporator is also called a ____.

A refrigeration system designed for the storage of flowers or candy is considered a ____ type.

A typical superheat for an evaporator operating under normal conditions would be ____.

When a system with a water-cooled condenser cycles off, the water regulating valve should ____.

A normally operating water-cooled condenser is operating with a 10° differential between water in and water out. If the amount of 85°F water going through the condenser is reduced, which of the following is a possible temperature of the water leaving the condenser?

A normally operating water-cooled condenser is operating with a 10° differential between water in and water out. If scale forms on the water tubes and the entering water is 85°F, which of the following is possible?

Which of the following would allow a system to operate more efficiently?

If an R-12 refrigeration system has its air-cooled condensing unit on a 100°F roof and the condenser outlet temperature (refrigerant) is 115°F, with how much subcooling is the condenser operating?

Which of the following condensers is the most efficient?

An air-cooled condenser that is operating in a climate that has four distinct seasons must ____.

What can be used to maintain the head pressure of a system with a water-cooled condenser?

Which of the following can be used to maintain the head pressure of a system with an air-cooled condenser?

The refrigerant in a condenser in a refrigeration system ____.

The condenser in a refrigeration system ____.

Mineral deposits in the water portion of a water-cooled condenser act as ____.

The water circuit in shell and coil and coil-type tube-in-a-tube condensers must be cleaned ____.

The shell and tube condenser is cleaned ____.

If the waterflow is reduced, the temperature difference across a condenser will ____.

In a water-cooled condenser, a regulating valve is used to control the ____.

Control of the head pressure in an air-cooled condenser is done by ____.

In a water-cooled condenser with dirty condenser tubes, the temperature difference between the refrigerant and the leaving water will be ____ when the tubes are clean.

Condensing temperatures in an air-cooled condensing unit can be reduced by ____.

A stamped plate evaporator usually does not use a fan to move air across it.

When the velocity of the air moving over an evaporator is slow, the "air film" acts as an insulator and slow the rate of heat exchange.

The refrigerant in the evaporator must be colder than the air passing over it for heat to transfer to the evaporator.

The device used to feed refrigerant to multiple circuits in an evaporator is called a flow circuit.

Fewer fins per inch on an evaporator allow more ice to build between defrost cycle.

Every central split cooling system manufactured in the USA today must have a Seasonal Energy Efficiency Ratio (Seer) of at least 10.

A water regulating valve helps maintain in a system's head pressure by modulating the flow of refrigerant through the condenser.

Evaporative condensers operate more efficiently in climates where the wet bulb temperature is a great deal lower than the dry bulb temperature.

The desired water flow through a condenser connecting to a recirculating water system is 3 gallons per minute.

If a spring pressure of a water regulating valve is increased, the system head pressure will also increase.

One large problem designer's face when designing air-cooled refrigeration and air conditioning equipment is a changing ambient from the changing seasons.

High head pressures from low ambients can cause insufficient refrigerant flow rates through metering devices, which in turn starve evaporators.

Low suction pressures, iced coils, short-cycling, and inefficient cooling can also result from low head pressures.

Hard starting may also occur in a low ambient conditions causing low head pressures.