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Engine · 623 questions

Refrigeration AC - USCG Exam Questions

Refrigeration cycles and components, compressors, refrigerants, and marine air conditioning systems.

Every question below is a real U.S. Coast Guard exam question with four choices. Answer one and the correct choice is revealed instantly, with the USCG reference and illustration where the question uses one.

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All Refrigeration AC questions

Questions 501–600 of 623 · page 6 of 7

  1. #914 What is the drive arrangement of refrigeration compressor shown in figure "B" of the illustration? Illustration GS-RA-41 illustration
  2. #915 Using the device shown in the illustration, which of the following statements is true when adding refrigerant as a vapor to the low side of the refrig... illustration
  3. #916 After the refrigerant has been recovered, leaks repaired if necessary, the system ideally should undergo a dehydration evacuation prior to recharging... illustration
  4. #917 Which of the following is true concerning the class "D" air conditioning system shown in the following illustration? Illustration GS-RA-42 illustration
  5. #918 Using the illustrated chart giving the boiling point of moisture at various depths of vacuum, with an ambient temperature of 72°F, what depth of v... illustration
  6. #919 When pumping down an air conditioning system to test the low-pressure cutout switch, assuming that the compressor is running, what should be done to i...
  7. #920 When recovering the remaining R-134a refrigerant from the centrifugal chiller shown in the illustration as a vapor using the recovery unit’s com... illustration
  8. #921 If the evaporator coil horizontal return line of a container refrigeration system is less than 0.875" (2.21 cm) in diameter (considered small); the th...
  9. #922 Which of the listed statements describes the method used to determine the amount of superheat present in the suction gas leaving the evaporator coil?... illustration
  10. #923 Of the various possible methods shown in the illustration, which is the correct method of attaching a TXV feeler bulb to a small large line (7/8" and... illustration
  11. #924 A high-pressure centrifugal chiller currently charged with R-134a is being evaluated for the need for leak testing. Using the leak test procedures dec... illustration
  12. #925 If a refrigeration compressor were short cycling on the low-pressure cutout switch, what is the most probable cause?
  13. #926 As shown in figure "B" of the illustrated self-contained recovery unit connection diagrams, what is the recovery method supported by the connection sc... illustration
  14. #927 What is the correct color-coding of refrigerant recovery cylinders regardless of the refrigerant contained within?
  15. #928 What must be done, at a minimum, before a system can legally be opened up for repairs while adhering to the prohibition against the venting of halogen...
  16. #929 Which of the following substances is normally classified as a low-pressure refrigerant?
  17. #930 What is the color-coding for a storage container of R-134a refrigerant?
  18. #931 Alkyl benzene ISO 32 cSt synthetic refrigerant oil is miscible and suitable to use with which of the following refrigerants?
  19. #932 The pressure in the part of a high-pressure refrigeration system about to be opened for a non-major repair should be brought to what value?
  20. #933 You are checking the supply chilled water temperature thermistor probe on a high-pressure hermetic centrifugal chiller. Using the illustrated chart, w... illustration
  21. #934 Which of the following illustrated thermal expansion valves would be appropriate to use on an evaporator coil with a 2 psi pressure drop, where extern... illustration
  22. #935 Through which of the components shown in the illustration is flash gas formation a normal occurrence? Illustration GS-RA-25 illustration
  23. #936 Which of the following illustrated expansion valves is designed to maintain a constant evaporator pressure rather than a constant evaporator superheat... illustration
  24. #937 In the multi-evaporator refrigeration system shown in the illustration, what is the proper name for the valve labeled "29"? Illustration GS-RA-12 illustration
  25. #938 An air-cooled refrigerated container unit using R-134a as a refrigerant has a box temperature set point of -15°F, but it is currently operating wi... illustration
  26. #939 If the running suction pressure at the refrigeration compressor of a TXV controlled air-cooled refrigeration system is below normal, which of the foll...
  27. #940 Which of the following statements is true concerning the illustrated gauge manifold set? Illustration GS-RA-01 illustration
  28. #941 Which of the following statements is true concerning the gauge labeled "A" of the illustrated gauge manifold set? Illustration GS-RA-01 illustration
  29. #942 Which of the illustrated gauges is capable of measuring vacuums at the micron level for the purpose of proving system dehydration during system evacua... illustration
  30. #943 In the presence of an open flame or hot surfaces, chlorinated fluorocarbon refrigerants decompose and form what chemical substance?
  31. #944 A container unit's microprocessor-controlled temperature controller is set at -28.9°C, appropriate for a frozen cargo of ice cream. In this mode o... illustration
  32. #945 Which of the following statements is true? Illustration GS-RA-12 illustration
  33. #946 What is the purpose of the low-pressure cut-out switch as used as a primary controller for a refrigeration system or unit?
  34. #947 A box solenoid valve used in a multi-box refrigeration system is operated by electromagnetic action by what control device?
  35. #948 Which of the following electrically operated refrigeration system valves would be most appropriate for use as a 2 position diverting hot gas bypass so... illustration
  36. #949 When checking zinc plates or pencil zincs in the refrigerating system condenser, what should you do?
  37. #950 The fluid used as a source of actuating power against the underside of the unloader power element piston of the refrigeration compressor capacity cont... illustration
  38. #951 During operating periods of a multi-box refrigeration system using a capacity controlled compressor, when all of the evaporators of a four box plant a... illustration
  39. #952 A refrigeration compressor used in a multi-box refrigeration system is designed with six of its eight cylinders able to be controlled for variable loa...
  40. #953 As shown in the illustrated refrigeration system piping schematic diagram with the various accessories and controls and equipped with an air-cooled co... illustration
  41. #954 In a refrigeration system, the valve shown in the illustration is used for what purpose? Illustration GS-RA-14 illustration
  42. #955 The set point adjustment of the device shown in the illustration is made by rotating what component? Illustration GS-RA-14 illustration
  43. #956 If it is necessary to increase the operating head pressure of the refrigeration system using the device shown in the illustration, what should be done... illustration
  44. #957 Which of the lettered components shown in the illustration indicates the high pressure cutout? Illustration GS-RA-12 illustration
  45. #958 When the relief valve opens on a refrigeration compressor discharge line, it discharges high-pressure refrigerant vapor to what location?
  46. #959 Alkyl benzene ISO 32 cSt synthetic refrigerant oil is miscible and suitable to use with which of the following refrigerants?
  47. #960 When checking zinc plates or pencil zincs in the refrigerating system condenser, what should you do?
  48. #961 The most cost-effective method of recovering refrigerant from a low-pressure chiller with more than 500 lbs of refrigerant and to meet EPA requirement...
  49. #962 Minor repairs may be performed on low-pressure refrigerant systems without recovering the refrigerant charge if the pressure in the system is raised t...
  50. #963 What is the wet bulb temperature of air if the dry bulb temperature of the air is 90 degrees and the relative humidity is 65%? Illustration GS-RA-22 illustration
  51. #964 What is one benefit of Maintenance of proper air circulation in an air conditioned cargo space?
  52. #965 In a two stage centrifugal air conditioning system, the liquid refrigerant passes through the condenser directly to what component?
  53. #966 In an air conditioning system, what is the name of the chamber where the duct-work originates?
  54. #967 A reheater in an air conditioning system performs what function?
  55. #968 The compressor used in a water-cooled air conditioning system is short-cycling. A service check determines that the suction pressure remains above the...
  56. #969 When pumping down an air conditioning system to test the low-pressure cutout switch, assuming that the compressor is running, what should be done to i...
  57. #970 Using the illustrated chart giving the boiling point of moisture at various depths of vacuum, with an ambient temperature of 72°F, what depth of v... illustration
  58. #971 When recovering the remaining R-134a refrigerant from the centrifugal chiller shown in the illustration as a vapor using the recovery unit's compresso... illustration
  59. #972 Heat is removed from the refrigerant circulating through the refrigeration system, shown in the illustration, by which component? Illustration GS-RA-1... illustration
  60. #973 A refrigeration unit will tend to short-cycle when operating under what conditions?
  61. #974 An air-cooled refrigerated container unit using R-134a as a refrigerant has a box temperature set point of -15°F, but it is currently operating wi... illustration
  62. #975 If the running suction pressure at the refrigeration compressor of a TXV controlled air-cooled refrigeration system is below normal, which of the foll...
  63. #976 What is the purpose of the pressure transducer as shown in the illustration? Illustration GS-RA-17 illustration
  64. #977 If the valve labeled "D" in the illustration is a suction service valve, what will the port labeled "7" be connected to? Illustration GS-RA-08 illustration
  65. #978 As shown in the illustrated LP centrifugal chiller pressure maintenance system, what is its functional purpose? Illustration GS-RA-40 illustration
  66. #979 Which lettered component, shown in the illustration, indicates the location of the receiver? Illustration GS-RA-12 illustration
  67. #980 As shown in the illustrated flow diagram for a self-contained recovery unit designed for the recovery of refrigerants from high pressure appliances as... illustration
  68. #981 In a refrigeration system featuring low side pump down prior to the automatic shut down of the compressor, the temperature of the refrigerated space i...
  69. #982 Which of the following statements is true? Illustration GS-RA-12 illustration
  70. #983 A box solenoid valve used in a multi-box refrigeration system is operated by electromagnetic action by what control device?
  71. #984 The low-pressure cutout switch settings vary with the refrigerant used and the temperature application. If the low-pressure cutout switch for a partic...
  72. #985 A container unit's microprocessor-controlled temperature controller is set at -28.9 ° C, appropriate for a frozen cargo of ice cream. In this mode... illustration
  73. #986 Which of the following electrically operated refrigeration system valves would be most appropriate for use as a 2 position diverting hot gas bypass so... illustration
  74. #987 Through which of the components shown in the illustration is flash gas formation a normal occurrence? Illustration GS-RA-25 illustration
  75. #988 Which of the statements listed is applicable to the thermostatic expansion valve shown in the illustration? Illustration GS-RA-07 illustration
  76. #989 In the multi-evaporator refrigeration system shown in the illustration, what is the proper name for the valve labeled "29"? Illustration GS-RA-12 illustration
  77. #990 Which of the following illustrated thermal expansion valves would be appropriate to use on an evaporator coil with a 2 psi pressure drop, where extern... illustration
  78. #991 Which of the following illustrated expansion valves is designed to maintain a constant evaporator pressure rather than a constant evaporator superheat... illustration
  79. #992 In the illustrated refrigeration system, what is the proper name for the component labeled "A"? Illustration GS-RA-12 illustration
  80. #993 What is the drive arrangement of refrigeration compressor shown in figure "B" of the illustration? Illustration GS-RA-41 illustration
  81. #994 If outside air at 80 degrees F and 70 percent relative humidity is conditioned, what will be the resulting dew point temperature of the air just befor... illustration
  82. #995 For the proper control of the air temperature in an air conditioning system using chilled water circulation, which of the listed conditions should rem...
  83. #996 Which of the processes listed would be the most satisfactory method to use to lower the humidity of the air being circulated by an air conditioning sy...
  84. #997 Which of the following is true concerning the class "A" air conditioning system shown in the illustration as used to condition the air of large public... illustration
  85. #998 A room humidistat initiates the lowering of the humidity of the conditioned supply air to a space, while the actual process is accomplished by what me...
  86. #999 To prevent the unnecessary loading of an air conditioning system while maintaining the designed dry bulb temperature and relative humidity in an air c...
  87. #1000 Which of the following methods is normally used to control the circulated air temperature of an air conditioning system using chilled water circulatio...
  88. #1001 The introduction of outside air to the air conditioning system is 90°F with a relative humidity of 60%. The air has been conditioned to 70°F w... illustration
  89. #1002 In an air conditioning system, moisture is removed from the air by what means?
  90. #1003 If the needle and seat assembly is excessively eroded, the valve cage assembly can be replaced. In replacing the original valve cage assembly rated at... illustration
  91. #1004 In the presence of an open flame or hot surfaces, chlorinated fluorocarbon refrigerants decompose and form what chemical substance?
  92. #1005 Personnel servicing refrigeration systems that exposes them to commonly used refrigerants should wear what type of personal protective equipment?
  93. #1006 If a refrigeration compressor were short-cycling on the low pressure cutout switch, what is the most probable cause?
  94. #1007 A refrigeration unit will tend to short-cycle when operating under what conditions?
  95. #1008 Which of the listed statements describes the method used to determine the amount of superheat present in the suction gas leaving the evaporator coil?... illustration
  96. #1009 The coil temperature measured at the expansion valve sensing bulb of an operating system is 10°F. The low side pressure with the compressor runnin... illustration
  97. #1010 Of the various possible methods shown in the illustration, which is the correct method of attaching a TXV feeler bulb to a large line (7/8" and larger... illustration
  98. #1011 If the evaporator coil horizontal return line of a container refrigeration system is less than 0.875" (2.21 cm) in diameter (considered small); the th...
  99. #1012 Expansion tanks when used in a ship's low temperature hot water heating system may be of the open or closed type. Referring to the illustrated central... illustration
  100. #1013 Referring to illustrated diagram, what type of HVAC system is shown? Illustration GS-RA-43 illustration

Refrigeration AC questions: what to expect

Q How many Refrigeration AC questions are in the Engine pool?

There are 623 Refrigeration AC questions on this site, every one released by the U.S. Coast Guard or taken from the National Maritime Center's sample examinations, with its correct answer. The exam draws its Refrigeration AC module from the same pool.

Q What score do I need to pass the Refrigeration AC module?

Most USCG exam modules, including Refrigeration AC, require 70 percent to pass. Rules of the Road modules require 90 percent.

Q Are these the real USCG Refrigeration AC exam questions?

Yes. They are the published U.S. Coast Guard questions, matched to the National Maritime Center's 2026 sample examinations. Answer any question to see the correct choice, the USCG reference and the illustration where the question uses one.

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