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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 101–200 of 623 · page 2 of 7

  1. #194 On a modern refrigerated container unit employing suction modulation for the purposes of capacity control and capacity limitation, what happens when t...
  2. #195 To prevent motor overload during start-up of a hermetically sealed centrifugal refrigeration system, what is true concerning the compressor suction ga...
  3. #197 In a multi-evaporator refrigeration system, a solenoid valve is installed in the liquid line prior to what device?
  4. #198 A liquid line solenoid valve controls refrigerant flow to the evaporator by what means?
  5. #199 How does a refrigeration solenoid valve differ from a modulating valve?
  6. #201 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...
  7. #202 The thermostat controlling the operation of the solenoid valve to a refrigerated box evaporator senses what temperature?
  8. #210 An arrow stamped on the valve body of a water regulating valve indicates which of the following?
  9. #212 The receiver used in a refrigeration system performs what essential function?
  10. #216 In a refrigeration plant, what is one vital purpose of the receiver?
  11. #219 In addition to pressure, most compound and standard pressure gauges used for refrigeration service are also provided with a scale indicating what para...
  12. #220 Hard drawn copper tubing is commonly used in larger refrigeration systems. What statement concerning its use is true?
  13. #221 In a large refrigeration system having more than one evaporator, a king solenoid valve should be installed in what location?
  14. #223 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...
  15. #227 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...
  16. #228 In a refrigeration system, what component is installed directly downstream of the thermal expansion valve?
  17. #229 Refrigeration systems using forced air circulation evaporators have a tendency to cause rapid dehydration of produce in chill boxes. Which of the foll...
  18. #230 In a dry-type direct expansion refrigeration evaporator, what is true concerning the evaporator coils?
  19. #234 If a condenser coil of an air-cooled container refrigeration system becomes dirty and requires cleaning, what would be an acceptable method of cleanin...
  20. #236 What is true concerning the accumulation of air and other non-condensable gases in a refrigeration system?
  21. #240 Constant superheat is maintained at the evaporator coil outlet of a refrigeration system or unit by the action of what device?
  22. #241 Besides the evaporator pressure, the thermal expansion valve reacts directly to changes in what parameter?
  23. #244 What is one function of the thermal expansion valve used in a refrigeration system?
  24. #246 In a refrigeration system, the pressure within the power element of a thermostatic expansion valve depends directly upon what factor?
  25. #248 A thermostatic expansion valve is properly controlling evaporator superheat. Adjusting this valve to lower the evaporator superheat setting will resul...
  26. #249 When replacing a thermostatic expansion valve power element, what is true concerning the thermal bulb?
  27. #251 Expansion valve maintenance should include which of the following procedures?
  28. #252 Which statement about calibrating a newly installed thermostatic expansion valve is correct?
  29. #253 Which of the installation steps listed is necessary for the proper operation of the thermostatic expansion valve?
  30. #255 What maintenance may be carried out on a thermostatic expansion valve?
  31. #256 When a thermostatic expansion valve is installed in a refrigerated container unit, the sensing bulb almost always requires insulation. Why is this so?
  32. #258 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?
  33. #259 If the superheat value of the thermostatic expansion valve is adjusted too high, what would be the result?
  34. #260 A small obstruction at the thermostatic expansion valve inlet will result in which of the following conditions?
  35. #261 An obstructed expansion valve may be indicated by an incompletely cooled evaporator and what other symptom?
  36. #263 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...
  37. #264 Moisture entering a typical refrigeration system will most likely produce what effect?
  38. #266 What is true concerning frost build-up on the evaporator coils of a multi-box direct expansion refrigeration system?
  39. #267 Some 'hot gas' defrost systems reheat the refrigerant just prior to its returning to the compressor for what purpose?
  40. #268 The FIRST thing to do to ensure that a refrigeration unit will not start while undergoing repairs is to do what?
  41. #269 Which of the precautions listed should be taken before opening any part of a refrigeration system for the purpose of accomplishing non-major repairs?
  42. #272 What is the maximum volume to which refillable refrigeration cylinders should be filled?
  43. #274 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...
  44. #275 A box solenoid valve used in a refrigeration system should be installed in what manner?
  45. #277 When using nitrogen to pressure leak test a system, the nitrogen cylinder should always be equipped with what device or feature?
  46. #278 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...
  47. #280 In a refrigeration system, from what location would air and non-condensable gases be removed?
  48. #281 Loss of refrigerant during the process of purging of air and non-condensable gases can be kept to a minimum by what action?
  49. #282 In a low-pressure centrifugal chiller, what is meant by the term 'high efficiency purge unit?'
  50. #285 Concerning the operation of refrigeration systems, frosting or sweating of a liquid line is usually indicative of what condition?
  51. #287 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...
  52. #288 Which of the conditions listed could cause excessively low refrigerant pressure at the compressor suction of a TXV controlled refrigeration system?
  53. #289 In an operating, water-cooled, multi-box refrigeration system, both low discharge and high suction pressures are being simultaneously experienced. The...
  54. #290 High suction pressure accompanied by low suction temperature to a refrigeration system compressor is caused by which of the following?
  55. #291 Low compressor head pressure in a refrigeration system can be caused by which of the following?
  56. #293 During tests to discover why a refrigeration compressor is running continuously, it is determined that the refrigerated space temperature is slightly...
  57. #294 When a refrigeration compressor motor fails to start, the FIRST thing that should be checked for is what?
  58. #295 If the refrigeration compressor crankcase is sweating or frosting and is operating with an unusual noise, what is most likely the cause?
  59. #296 If a refrigeration system were short of refrigerant, besides an elevated box temperature, what would be an observable symptom?
  60. #298 If a refrigeration system, equipped with a reciprocating compressor, has a liquid-line solenoid valve that is leaking during the 'off' cycle, what wou...
  61. #299 A refrigeration unit will tend to short cycle when operating under what conditions?
  62. #300 If a refrigeration compressor had developed a slightly high suction pressure accompanied with an abnormally low suction temperature, the problem could...
  63. #301 An excessive charge of refrigerant in a thermostatically controlled, air-cooled, refrigeration system using a TXV as an expansion device can cause whi...
  64. #302 If a refrigeration compressor using a thermostat as a primary controller is running continuously without significantly lowering the temperature in the...
  65. #303 In a refrigeration system, the push-pull technique can be used for the recovery of the refrigerant in what state?
  66. #307 Which recovery procedure should be used to minimize the loss of oil from the system during the recovery of refrigerant from small appliances such as a...
  67. #308 What is true concerning highly contaminated refrigerant recovered from burned out small appliances?
  68. #309 Technicians servicing small refrigeration appliances can employ what type of recovery equipment?
  69. #310 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...
  70. #315 Before charging a refrigeration unit, unless quick disconnect fittings are used, the refrigerant charging hoses should be prepared in what way?
  71. #317 Concerning the charging of refrigerant into a vapor compression refrigerating system, which of the following is true?
  72. #319 How should small appliances with less than three pounds of refrigerant be charged with refrigerant?
  73. #321 Charging liquid HCFC-123 into a system under a deep vacuum could cause what to happen unless necessary precautions are taken?
  74. #322 When a refrigeration system is being topped off with a small amount of refrigerant through the low side with the compressor running, what should be do...
  75. #323 Which of the valves listed is normally closed when charging the refrigeration system through the high side?
  76. #325 Coast Guard Regulations (46 CFR Part 58) require a method for the relieving pressure of an over pressurized refrigeration system. Which of the followi...
  77. #326 Coast Guard Regulations (46 CFR Part 113) require refrigerated spaces that can be locked from the outside and that cannot be opened from the inside to...
  78. #327 With regards to shipboard refrigeration systems, after July 1, 1992, what action became illegal?
  79. #329 According to 46 CFR, Part 58, for protection purposes, what is required of all refrigeration systems?
  80. #330 What would be an example of a small appliance as defined in the EPA Clean Air Act rules?
  81. #332 If you find the pressure of a refrigeration system containing a Class I or Class II refrigerant to be opened for the accomplishment of repairs is 0 ps...
  82. #334 All shipboard personnel responsible for the maintenance and repair of air conditioning systems using refrigerants covered under the EPA Clean Air Act...
  83. #336 Persons recovering refrigerant from small appliances must be certified as what type of technician under the EPA Clean Air Act rules?
  84. #338 Within the territorial limits of the United States, violations of the Clean Air Act of 1990, that includes the intentional release of R-11, R-12, R-22...
  85. #339 For safe storage, the maximum allowable temperature to which refrigerant bottles should be exposed is what temperature?
  86. #340 Overfilling a refrigerant container is extremely dangerous because of the high pressures generated. The generation of pressure is the result of what?
  87. #341 Personnel servicing refrigeration systems and subject to the exposure to commonly used refrigerants should wear what type of personal protective equip...
  88. #343 Why can CFC or HCFC refrigerants leaking into a confined space or in limited surroundings cause suffocation?
  89. #346 When repairing a refrigeration system, a swaging tool set would be used to carry out which of the following operations?
  90. #348 What is the purpose of running a refrigeration compressor in short intermittent spurts or throttling the suction isolation valve when starting the sys...
  91. #349 When starting a reciprocating refrigeration compressor that has been shut down for a period of time, you should manually throttle which valve?
  92. #350 When opening or closing compressor service and line isolation valves on a typical refrigeration system that is fitted with packed valves, what must yo...
  93. #351 In an air conditioning system, what is the name of the chamber where the duct-work originates?
  94. #352 In a two stage centrifugal air conditioning system, the liquid refrigerant passes through the condenser directly to what component?
  95. #353 A reheater in an air conditioning system performs what function?
  96. #354 What is one benefit of Maintenance of proper air circulation in an air conditioned cargo space?
  97. #355 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
  98. #356 In general, the thermal bulb for a thermal expansion valve used in a reciprocating air conditioning system is usually charged with what substance?
  99. #357 To prevent the unnecessary loading of an air conditioning system while maintaining the designed dry bulb temperature and relative humidity in an air c...
  100. #358 Which of the following methods is normally used to control the circulated air temperature of an air conditioning system using chilled water circulatio...

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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