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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 1–100 of 623 · page 1 of 7

  1. #1 Traditionally, which of the listed refrigerants has been more suitable than the others for use in a centrifugal refrigeration compressor?
  2. #2 Which of the fluids listed is suitable for use as a secondary refrigerant?
  3. #5 Which of the following refrigerants is chlorine free and safe regarding atmospheric ozone depletion?
  4. #7 What is the most important consideration in selecting a lubricating oil for use in a refrigeration compressor?
  5. #10 The lubrication oil in the crankcase of a refrigeration compressor that is shut down is heated. For what purpose is this done?
  6. #11 The "tare weight" of a refrigerant storage cylinder refers to what weight?
  7. #13 The term 'oil foaming' in refrigeration practice, is used to describe what event?
  8. #16 At ambient temperature and atmospheric pressure, what is the status of R-134a?
  9. #18 What is the physical state and pressure condition of refrigerant as it leaves a receiver in a typical refrigeration system?
  10. #19 Refrigerant entering the compressor of a refrigeration system should be in which of the following conditions?
  11. #26 Before charging a refrigeration unit, unless quick disconnect fittings are used, the refrigerant charging hoses should be prepared in what way?
  12. #27 The amount of HCFC-123 in a storage cylinder is measured by what means?
  13. #29 Loss of refrigerant during the process of purging of air and non-condensable gases can be kept to a minimum by what action?
  14. #33 If passive recovery is used on a small appliance fitted with a capillary tube as a metering device with a non-operating compressor, the recovery shoul...
  15. #34 In a low-pressure centrifugal chiller, what is meant by the term 'high efficiency purge unit?'
  16. #39 Which of the valves listed is normally closed when charging the refrigeration system through the high side?
  17. #42 In reclaiming recovered refrigerant, which type of contamination will the reclamation process be unable to separate?
  18. #43 In a refrigeration system, the push-pull technique can be used for the recovery of the refrigerant in what state?
  19. #48 What is true concerning highly contaminated refrigerant recovered from burned out small appliances?
  20. #49 Technicians servicing small refrigeration appliances can employ what type of recovery equipment?
  21. #55 What is true concerning frost build-up on the evaporator coils of a multi-box direct expansion refrigeration system?
  22. #59 If the combination moisture indicator and sight glass indicates an accumulation of moisture within the system, which of the listed procedures would be...
  23. #60 In addition to the drive belt itself, a V-belt that is tensioned too tight will cause excessive wear to what other drive component?
  24. #61 When one belt of a multiple V-belt drive requires replacing, what will be required?
  25. #62 Excessively tight drive belts installed between a motor and a refrigeration compressor pulley may cause what condition?
  26. #63 When installing a mechanical shaft seal on a refrigeration compressor, extreme care must be taken to prevent what from happening?
  27. #64 If the discharge reed valves used in a refrigeration compressor are leaking badly, what statement is true?
  28. #68 When replacing a thermostatic expansion valve power element, what is true concerning the thermal bulb?
  29. #69 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...
  30. #71 Concerning the operation of refrigeration systems, frosting or sweating of a liquid line is usually indicative of what condition?
  31. #72 If an abnormally large difference is maintained between the evaporator refrigerant temperature and the box air temperature within the refrigerated com...
  32. #73 What is the color of the flame produced by a halide torch when there is no halogenated refrigerant present at the location of the exploring tube?
  33. #74 To test for a suspected large refrigerant leak from an R-22 refrigeration system in an enclosed area, how should this be done?
  34. #76 Which of the following statements is correct concerning the testing of an R-22 refrigeration system for leaks in an enclosed compartment with a halide...
  35. #80 Moisture in a refrigeration system can cause which of the following conditions?
  36. #81 If a refrigeration system were short of refrigerant, besides an elevated box temperature, what would be an observable symptom?
  37. #84 When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, what should be done to compensate for or t...
  38. #87 Which of the following statements describes the accepted method for testing a thermostatic expansion valve?
  39. #88 If the superheat setting of a thermostatic expansion valve is set too low, what would be the result, assuming that the system has a single evaporator?
  40. #89 If the superheat value of the thermostatic expansion valve is adjusted too high, what would be the result?
  41. #90 A small obstruction at the thermostatic expansion valve inlet will result in which of the following conditions?
  42. #91 Excessive, prolonged oil foaming in the crankcase of a refrigeration compressor can result in what condition?
  43. #92 Which of the following conditions would indicate that the liquid line strainer in a refrigeration system has become excessively restricted and require...
  44. #94 If the compressor is heard to knock while pumping down the low side for repairs, but otherwise the compressor sounds normal; this is a possible indica...
  45. #97 Why are dehydrators usually located in the liquid line of refrigeration systems?
  46. #98 In a refrigeration system, silica gel is found in what component?
  47. #99 Standard filter/driers used in many commercial type refrigeration units may contain what type of substance?
  48. #100 Which of the devices listed will indicate whether or not a refrigeration system's dehydrator continues to be capable of removing moisture from the cir...
  49. #101 Capacity control of a centrifugal refrigeration compressor can be accomplished by what means?
  50. #104 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...
  51. #105 On a modern refrigerated container unit employing suction modulation for the purposes of capacity control and capacity limitation, what happens when t...
  52. #107 A box solenoid valve used in a refrigeration system should be installed in what manner?
  53. #109 In a multi-evaporator refrigeration system, a solenoid valve is installed in the liquid line prior to what device?
  54. #111 How does a refrigeration solenoid valve differ from a modulating valve?
  55. #113 In a refrigeration system that is not protected by a water failure switch, if the cooling water to the condenser fails, what will be the result for pr...
  56. #120 Rather than design an infinite variety of thermostatic expansion valve sizes to accommodate different capacities for heat removal, some manufacturers...
  57. #122 Besides the evaporator pressure, the thermal expansion valve reacts directly to changes in what parameter?
  58. #123 The receiver used in a refrigeration system performs what essential function?
  59. #127 In a refrigeration plant, what is one vital purpose of the receiver?
  60. #132 The safety heads of most large reciprocating compressors used in refrigeration systems are held in place by what means?
  61. #135 A device used to hold open the refrigeration compressor suction valve during starting to reduce the compression load is called what?
  62. #137 Refrigeration systems using forced air circulation evaporators have a tendency to cause rapid dehydration of produce in chill boxes. Which of the foll...
  63. #142 If a condenser coil of an air-cooled container refrigeration system becomes dirty and requires cleaning, what would be an acceptable method of cleanin...
  64. #144 For safe storage, the maximum allowable temperature to which refrigerant bottles should be exposed is what temperature?
  65. #146 Personnel servicing refrigeration systems and subject to the exposure to commonly used refrigerants should wear what type of personal protective equip...
  66. #149 Which of the precautions listed should be taken before opening any part of a refrigeration system for the purpose of accomplishing non-major repairs?
  67. #150 Why can CFC or HCFC refrigerants leaking into a confined space or in limited surroundings cause suffocation?
  68. #151 Overfilling a refrigerant container is extremely dangerous because of the high pressures generated. The generation of pressure is the result of what?
  69. #153 Traditionally, which of the listed refrigerants has been more suitable than the others for use in a centrifugal refrigeration compressor?
  70. #154 Which of the fluids listed is suitable for use as a secondary refrigerant?
  71. #156 The amount of HCFC-123 in a storage cylinder is measured by what means?
  72. #159 The gas that exists in the stratosphere forming a protective shield that helps to protect the environment from the harmful effects ultraviolet radiati...
  73. #160 The "tare weight" of a refrigerant storage cylinder refers to what weight?
  74. #161 The term 'oil foaming' in refrigeration practice, is used to describe what event?
  75. #162 What is the physical state and pressure condition of refrigerant as it enters the condenser of a typical refrigeration system?
  76. #163 What is the physical state and pressure condition of refrigerant as it leaves a receiver in a typical refrigeration system?
  77. #164 What is the pressure and condition of the refrigerant entering the receiver of a refrigeration system?
  78. #165 The safety heads of most large reciprocating compressors used in refrigeration systems are held in place by what means?
  79. #167 A device used to hold open the refrigeration compressor suction valve during starting to reduce the compression load is called what?
  80. #168 The carbon seal ring of a refrigeration compressor crankshaft mechanical seal is held in position against the stationary ring face by using what devic...
  81. #170 If the discharge reed valves used in a refrigeration compressor are leaking badly, what statement is true?
  82. #171 In addition to the drive belt itself, a V-belt that is tensioned too tight will cause excessive wear to what other drive component?
  83. #172 When one belt of a multiple V-belt drive requires replacing, what will be required?
  84. #173 Excessively tight drive belts installed between a motor and a refrigeration compressor pulley may cause what condition?
  85. #174 When installing a mechanical shaft seal on a refrigeration compressor, extreme care must be taken to prevent what from happening?
  86. #175 A reciprocating refrigeration compressor may be tested for leaking discharge valves by stopping the compressor, turning the discharge service valve al...
  87. #176 Unusual noise coming from a refrigeration compressor can be caused by which of the following conditions?
  88. #177 Which of the listed statements describes the reason why oil foaming occurs when starting a refrigeration compressor?
  89. #178 Leaking suction valves in a refrigeration compressor are indicated by which of the following?
  90. #180 Why are dehydrators usually located in the liquid line of refrigeration systems?
  91. #181 In a refrigeration system, silica gel is found in what component?
  92. #182 Standard filter/driers used in many commercial type refrigeration units may contain what type of substance?
  93. #183 Which of the devices listed will indicate whether or not a refrigeration system's dehydrator continues to be capable of removing moisture from the cir...
  94. #184 Moisture is removed from a refrigeration system by what action?
  95. #187 For most multi-box refrigeration systems, the refrigerant sight glass would be located where in the system?
  96. #188 A liquid indicator sight glass is useful in determining whether or not a refrigeration system is sufficiently charged. Where is it generally located i...
  97. #189 The primary purpose of the liquid line strainer used in a refrigeration system is to prevent dirt and scale from entering what system component(s)?
  98. #190 Capacity control of a centrifugal refrigeration compressor can be accomplished by what means?
  99. #192 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...
  100. #193 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...

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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