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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 201–300 of 623 · page 3 of 7

  1. #359 For the proper control of the air temperature in an air conditioning system using chilled water circulation, which of the listed conditions should rem...
  2. #360 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...
  3. #361 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...
  4. #362 In an air conditioning system, moisture is removed from the air by what means?
  5. #364 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
  6. #365 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
  7. #367 Concerning the arrangement of equipment and associated hoses shown in the illustration, what statement is true? Illustration GS-RA-59 illustration
  8. #368 To add small amounts of refrigerant to the low side of an air conditioning system, the refrigerant should be introduced through a particular valve and...
  9. #369 To add refrigerant to the high side of an air conditioning system, you should close the king valve and introduce the refrigerant through what valve in...
  10. #372 The compressor used in a water-cooled air conditioning system is short cycling. A service check determines that the suction pressure remains above the...
  11. #374 Concerning the arrangement of equipment and associated hoses shown in the illustration, what statement is true? Illustration GS-RA-58 illustration
  12. #375 The surging that occurs in a centrifugal air conditioning compressor is a result of what conditions?
  13. #376 In an air conditioning system, low discharge head pressure associated with a reciprocating compressor can be the result of what condition?
  14. #378 Sludge may form in the crankcase of an air conditioning compressor as a result of what condition?
  15. #379 As shown in the illustrated LP centrifugal chiller high efficiency purge recovery unit piping schematic, what statement is true concerning the vacuum... illustration
  16. #380 Traditionally, which of the listed refrigerants has been more suitable than the others for use in a centrifugal refrigeration compressor?
  17. #381 Which of the fluids listed is suitable for use as a secondary refrigerant?
  18. #383 The amount of HCFC-123 in a storage cylinder is measured by what means?
  19. #384 Which of the following substances is normally classified as a low pressure refrigerant?
  20. #386 The gas that exists in the stratosphere forming a protective shield that helps to protect the environment from the harmful effects ultraviolet radiati...
  21. #387 The "tare weight" of a refrigerant storage cylinder refers to what weight?
  22. #388 The safety heads of most large reciprocating compressors used in refrigeration systems are held in place by what means?
  23. #390 A device used to hold open the refrigeration compressor suction valve during starting to reduce the compression load is called what?
  24. #391 The carbon seal ring of a refrigeration compressor crankshaft mechanical seal is held in position against the stationary ring face by using what devic...
  25. #393 If the discharge reed valves used in a refrigeration compressor are leaking badly, what statement is true?
  26. #394 In addition to the drive belt itself, a V-belt that is tensioned too tight will cause excessive wear to what other drive component?
  27. #395 When one belt of a multiple V-belt drive requires replacing, what will be required?
  28. #396 Excessively tight drive belts installed between a motor and a refrigeration compressor pulley may cause what condition?
  29. #397 When installing a mechanical shaft seal on a refrigeration compressor, extreme care must be taken to prevent what from happening?
  30. #398 If a refrigeration system were short of refrigerant, besides an elevated box temperature, what would be an observable symptom?
  31. #399 A reciprocating refrigeration compressor may be tested for leaking discharge valves by stopping the compressor, turning the discharge service valve al...
  32. #400 Which of the conditions listed could cause excessively low refrigerant pressure at the compressor suction of a TXV controlled refrigeration system?
  33. #401 Low compressor head pressure in a refrigeration system can be caused by which of the following?
  34. #402 An excessive charge of refrigerant in a thermostatically controlled, air-cooled, refrigeration system using a TXV as an expansion device can cause whi...
  35. #403 In an operating, water-cooled, multi-box refrigeration system, both low discharge and high suction pressures are being simultaneously experienced. The...
  36. #404 If a refrigeration system, equipped with a reciprocating compressor, has a liquid-line solenoid valve that is leaking during the 'off' cycle, what wou...
  37. #405 Unusual noise coming from a refrigeration compressor can be caused by which of the following conditions?
  38. #406 Which of the listed statements describes the reason why oil foaming occurs when starting a refrigeration compressor?
  39. #408 If a refrigeration compressor were short cycling on the low pressure cutout switch, what is the most probable cause?
  40. #410 In a multi-evaporator refrigeration system, a solenoid valve is installed in the liquid line prior to what device?
  41. #411 A liquid line solenoid valve controls refrigerant flow to the evaporator by what means?
  42. #412 How does a refrigeration solenoid valve differ from a modulating valve?
  43. #415 The thermostat controlling the operation of the solenoid valve to a refrigerated box evaporator senses what temperature?
  44. #418 What is the purpose of the low pressure cut-out switch as used as a primary controller for a refrigeration system or unit?
  45. #419 The sensing line for the low pressure cutout switch for a refrigeration system is typically connected at what location?
  46. #420 Which of the listed operations will cause an automatically controlled refrigeration compressor to restart if the system features a pump-down cycle?
  47. #422 Capacity control of a centrifugal refrigeration compressor can be accomplished by what means?
  48. #426 On a modern refrigerated container unit employing suction modulation for the purposes of capacity control and capacity limitation, what happens when t...
  49. #427 To prevent motor overload during start-up of a hermetically sealed centrifugal refrigeration system, what is true concerning the compressor suction ga...
  50. #432 An arrow stamped on the valve body of a water regulating valve indicates which of the following?
  51. #433 During the initial cooling down of a box temperature in a refrigeration system, which of the devices listed is used to prevent excessive gas pressure...
  52. #434 The rupture disc on a low pressure centrifugal refrigeration unit is used as an over pressure protection device and is set to relieve at 15 psig and i...
  53. #437 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...
  54. #438 The receiver used in a refrigeration system performs what essential function?
  55. #439 Refrigeration system isolation valves are specially designed with a back-seat, as well as a front-seat. For what purpose are these valves designed in...
  56. #442 In a refrigeration plant, what is one vital purpose of the receiver?
  57. #445 In addition to pressure, most compound and standard pressure gauges used for refrigeration service are also provided with a scale indicating what para...
  58. #446 Hard drawn copper tubing is commonly used in larger refrigeration systems. What statement concerning its use is true?
  59. #447 In a large refrigeration system having more than one evaporator, a king solenoid valve should be installed in what location?
  60. #449 In a refrigeration system, what component is installed directly downstream of the thermal expansion valve?
  61. #450 Refrigeration systems using forced air circulation evaporators have a tendency to cause rapid dehydration of produce in chill boxes. Which of the foll...
  62. #451 In a dry-type direct expansion refrigeration evaporator, what is true concerning the evaporator coils?
  63. #452 Zinc plates commonly found in refrigeration systems and used as sacrificial anodes are located where?
  64. #455 If a condenser coil of an air-cooled container refrigeration system becomes dirty and requires cleaning, what would be an acceptable method of cleanin...
  65. #460 Rather than design an infinite variety of thermostatic expansion valve sizes to accommodate different capacities for heat removal, some manufacturers...
  66. #461 Constant superheat is maintained at the evaporator coil outlet of a refrigeration system or unit by the action of what device?
  67. #462 Besides the evaporator pressure, the thermal expansion valve reacts directly to changes in what parameter?
  68. #465 What is one function of the thermal expansion valve used in a refrigeration system?
  69. #466 When a refrigeration compressor is in the 'off' cycle, the thermal expansion valve will react in what way?
  70. #467 In a refrigeration system, the pressure within the power element of a thermostatic expansion valve depends directly upon what factor?
  71. #468 In a refrigeration system, the bulb for the thermal expansion valve is always located where?
  72. #469 Concerning the proper installation of the sensing bulb of a thermal expansion valve that is attached to the evaporator tail coil on a horizontal run,...
  73. #471 When the sensing bulb of a thermostatic expansion valve is charged with a fluid different from the charge used in the system, what name of the charge...
  74. #472 A typical shipboard domestic multi-box refrigeration system operates with one compressor and condenser. What is the purpose of the sensing line connec...
  75. #473 Refrigerant flow through a thermostatic expansion valve is greatest under what conditions?
  76. #474 In a vapor compression type refrigeration cycle, the refrigerant temperature decreases the most when passing through which system component?
  77. #475 The thermostatic expansion valve in a refrigeration system further opens when the diaphragm flexes downward. With all other conditions being the same,...
  78. #476 In refrigeration systems with multiple evaporators, the metering of refrigerant to each refrigerated space evaporator is accomplished by what device?
  79. #478 A thermostatic expansion valve is properly controlling evaporator superheat. Adjusting this valve to lower the evaporator superheat setting will resul...
  80. #479 When replacing a thermostatic expansion valve power element, what is true concerning the thermal bulb?
  81. #481 Expansion valve maintenance should include which of the following procedures?
  82. #482 Which statement about calibrating a newly installed thermostatic expansion valve is correct?
  83. #483 Which of the installation steps listed is necessary for the proper operation of the thermostatic expansion valve?
  84. #485 What maintenance may be carried out on a thermostatic expansion valve?
  85. #486 When a thermostatic expansion valve is installed in a refrigerated container unit, the sensing bulb almost always requires insulation. Why is this so?
  86. #487 Which of the following statements describes the accepted method for testing a thermostatic expansion valve?
  87. #489 Concerning the proper installation of the sensing bulb of a thermal expansion valve that is attached to the evaporator tail coil on a horizontal run,...
  88. #491 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?
  89. #492 If the superheat value of the thermostatic expansion valve is adjusted too high, what would be the result?
  90. #493 A small obstruction at the thermostatic expansion valve inlet will result in which of the following conditions?
  91. #494 An obstructed expansion valve may be indicated by an incompletely cooled evaporator and what other symptom?
  92. #496 Vapor bubbles present in the liquid upon arrival to the thermal expansion valve in a refrigeration system may cause erosion of the expansion valve's n...
  93. #497 Moisture entering a typical refrigeration system will most likely produce what effect?
  94. #498 Concerning the operation of refrigeration systems, frosting or sweating of a liquid line is usually indicative of what condition?
  95. #500 If increasing the cooling water flow to a refrigeration condenser fails to lower the condenser pressure, the probable cause may be due to what conditi...
  96. #502 In an operating, water-cooled, multi-box refrigeration system, both low discharge and high suction pressures are being simultaneously experienced. The...
  97. #503 High suction pressure accompanied by low suction temperature to a refrigeration system compressor is caused by which of the following?
  98. #504 Low compressor head pressure in a refrigeration system can be caused by which of the following?
  99. #508 During tests to discover why a refrigeration compressor is running continuously, it is determined that the refrigerated space temperature is slightly...
  100. #509 When a refrigeration compressor motor fails to start, the FIRST thing that should be checked for is what?

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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