Assessment Test

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1. When a thermostatic expansion valve is installed in a refrigerated container unit, the sensing bulb almost always requires insulation. Why is this so?


2. Which of the following statements describes the accepted method for testing a thermostatic expansion valve?


3. 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?


4. If the superheat value of the thermostatic expansion valve is adjusted too high, what would be the result?


5. A small obstruction at the thermostatic expansion valve inlet will result in which of the following conditions?


6. An obstructed expansion valve may be indicated by an incompletely cooled evaporator and what other symptom?


7. 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 needle and seat. This, in turn, could cause what condition?


8. Moisture entering a typical refrigeration system will most likely produce what effect?


9. Concerning the operation of refrigeration systems, frosting or sweating of a liquid line is usually indicative of what condition?


10. If increasing the cooling water flow to a refrigeration condenser fails to lower the condenser pressure, the probable cause may be due to what condition?


11. Which of the conditions listed could cause excessively low refrigerant pressure at the compressor suction of a TXV controlled refrigeration system?


12. In an operating, water-cooled, multi-box refrigeration system, both low discharge and high suction pressures are being simultaneously experienced. The probable cause for this condition is which of the following?


13. High suction pressure accompanied by low suction temperature to a refrigeration system compressor is caused by which of the following?


14. Low compressor head pressure in a refrigeration system can be caused by which of the following?


15. If the running suction pressure at the refrigeration compressor of a TXV controlled air-cooled refrigeration system is below normal, which of the following can be a cause?


16. The compressor on the ships service refrigeration system starts up but stops after a brief period of running. Subsequent attempts to start it produce no result. What control component would you suspect?


17. During tests to discover why a refrigeration compressor is running continuously, it is determined that the refrigerated space temperature is slightly above normal without ever reaching the desired minimum temperature. Suction and discharge pressures are normal for the corresponding box temperature. In this situation, what should you suspect?


18. When a refrigeration compressor motor fails to start, the FIRST thing that should be checked for is what?


19. If the refrigeration compressor crankcase is sweating or frosting and is operating with an unusual noise, what is most likely the cause?


20. If a refrigeration system were short of refrigerant, besides an elevated box temperature, what would be an observable symptom?


21. If a refrigeration compressor were short cycling on the low pressure cutout switch, what is the most probable cause?


22. Which of the fluids listed is suitable for use as a secondary refrigerant?


23. Alkylbenzene ISO 32 cSt synthetic refrigerant oil is miscible and suitable to use with which of the following refrigerants?


24. The amount of HCFC-123 in a storage cylinder is measured by what means?


25. Which of the following substances is normally classified as a low pressure refrigerant?


26. What is the color coding for a storage container of R-134a refrigerant?


27. The gas that exists in the stratosphere forming a protective shield that helps to protect the environment from the harmful effects ultraviolet radiation is called what?


28. The "tare weight" of a refrigerant storage cylinder refers to what weight?


29. The safety heads of most large reciprocating compressors used in refrigeration systems are held in place by what means?


30. A device used to hold open the refrigeration compressor suction valve during starting to reduce the compression load is called what?


31. The carbon seal ring of a refrigeration compressor crankshaft mechanical seal is held in position against the stationary ring face by using what device?


32. If the discharge reed valves used in a refrigeration compressor are leaking badly, what statement is true?


33. In addition to the drive belt itself, a V-belt that is tensioned too tight will cause excessive wear to what other drive component?


34. When one belt of a multiple V-belt drive requires replacing, what will be required?


35. Excessively tight drive belts installed between a motor and a refrigeration compressor pulley may cause what condition?


36. When installing a mechanical shaft seal on a refrigeration compressor, extreme care must be taken to prevent what from happening?


37. If a refrigeration system were short of refrigerant, besides an elevated box temperature, what would be an observable symptom?


38. A reciprocating refrigeration compressor may be tested for leaking discharge valves by stopping the compressor, turning the discharge service valve all the way in, and then turning the compressor over by hand. If the discharge valves are leaking, the compound gage will show pressures which react in which way?


39. Which of the conditions listed could cause excessively low refrigerant pressure at the compressor suction of a TXV controlled refrigeration system?


40. Low compressor head pressure in a refrigeration system can be caused by which of the following


41. An excessive charge of refrigerant in a thermostatically controlled, air-cooled, refrigeration system using a TXV as an expansion device can cause which of the following?


42. In an operating, water-cooled, multi-box refrigeration system, both low discharge and high suction pressures are being simultaneously experienced. The probable cause for this condition is which of the following?


43. If a refrigeration system, equipped with a reciprocating compressor, has a liquid-line solenoid valve that is leaking during the 'off' cycle, what would this cause?


44. Unusual noise coming from a refrigeration compressor can be caused by which of the following conditions?


45. Which of the listed statements describes the reason why oil foaming occurs when starting a refrigeration compressor?


46. A refrigeration unit will tend to short cycle when operating under what conditions?


47. If a refrigeration compressor were short cycling on the low pressure cutout switch, what is the most probable cause?


48. A box solenoid valve used in a multi-box refrigeration system is operated by electro-magnetic action by what control device?


49. In a multi-evaporator refrigeration system, a solenoid valve is installed in the liquid line prior to what device?


50. A liquid line solenoid valve controls refrigerant flow to the evaporator by what means?


51. How does a refrigeration solenoid valve differ from a modulating valve?


52. In a refrigeration system featuring low-side pump down prior to the automatic shut down of the compressor, the temperature of the refrigerated space is controlled by the action of a thermostat wired to what device?


53. The thermostat controlling the operation of the solenoid valve to a refrigerated box evaporator senses what temperature?


54. What is the purpose of the low pressure cut-out switch as used as a primary controller for a refrigeration system or unit?


55. The sensing line for the low pressure cutout switch for a refrigeration system is typically connected at what location?


56. Which of the listed operations will cause an automatically controlled refrigeration compressor to restart if the system features a pump-down cycle?


57. Capacity control of a centrifugal refrigeration compressor can be accomplished by what means?


58. On a modern refrigerated container unit employing suction modulation for the purposes of capacity control and capacity limitation, what happens when the applied voltage and current draw associated with the normally open (NO) suction modulation valve located in the suction line both increase?


59. To prevent motor overload during start-up of a hermetically sealed centrifugal refrigeration system, what is true concerning the compressor suction gas variable inlet guide vanes?


60. An arrow stamped on the valve body of a water regulating valve indicates which of the following?


61. 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 at the compressor suction for the purpose of prevention of overloading of the compressor driver?


62. 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 is most likely to lift when the compressor is idle? Where is the rupture disc located?


63. When the relief valve opens on a refrigeration compressor discharge line, it discharges high pressure refrigerant vapor to what location?


64. 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 protective purposes?


65. The receiver used in a refrigeration system performs what essential function?


66. 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 this way?


67. In a refrigeration plant, what is one vital purpose of the receiver?


68. In addition to pressure, most compound and standard pressure gauges used for refrigeration service are also provided with a scale indicating what parameter?


69. Hard drawn copper tubing is commonly used in larger refrigeration systems. What statement concerning its use is true?


70. In a large refrigeration system having more than one evaporator, a king solenoid valve should be installed in what location?


71. In a refrigeration system, what component is installed directly downstream of the thermal expansion valve?


72. Refrigeration systems using forced air circulation evaporators have a tendency to cause rapid dehydration of produce in chill boxes. Which of the following will minimize this dehydration?


73. In a dry-type direct expansion refrigeration evaporator, what is true concerning the evaporator coils?


74. Zinc plates commonly found in refrigeration systems and used as sacrificial anodes are located where?


75. Seawater or low temperature central fresh water is typically provided to a ship's stores refrigeration plant for what purpose?


76. If a condenser coil of an air-cooled container refrigeration system becomes dirty and requires cleaning, what would be an acceptable method of cleaning?


77. When checking zinc plates, or pencil Zincs in the refrigerating system condenser, what should you do?


78. What is true concerning the accumulation of air and other non-condensable gases in a refrigeration system?


79. Rather than design an infinite variety of thermostatic expansion valve sizes to accommodate different capacities for heat removal, some manufacturers use a few standard valve body sizes in conjunction with what other feature?


80. Constant superheat is maintained at the evaporator coil outlet of a refrigeration system or unit by the action of what device?


81. Besides the evaporator pressure, the thermal expansion valve reacts directly to changes in what parameter?


82. What is one function of the thermal expansion valve used in a refrigeration system?


83. When a refrigeration compressor is in the 'off' cycle, the thermal expansion valve will react in what way?


84. In a refrigeration system, the pressure within the power element of a thermostatic expansion valve depends directly upon what factor?


85. In a refrigeration system, the bulb for the thermal expansion valve is always located where?


86. 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, what statement is true?


87. 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 is associated with the power element?


88. A typical shipboard domestic multi-box refrigeration system operates with one compressor and condenser. What is the purpose of the sensing line connected to the thermal bulb at the evaporator coil outlet?


89. Refrigerant flow through a thermostatic expansion valve is greatest under what conditions?


90. In a vapor compression type refrigeration cycle, the refrigerant temperature decreases the most when passing through which system component?


91. evaporator


92. The thermostatic expansion valve in a refrigeration system further opens when the diaphragm flexes downward. With all other conditions being the same, what single condition causes this?


93. In refrigeration systems with multiple evaporators, the metering of refrigerant to each refrigerated space evaporator is accomplished by what device?


94. A thermostatic expansion valve is properly controlling evaporator superheat. Adjusting this valve to lower the evaporator superheat setting will result in which of the following?


95. When replacing a thermostatic expansion valve power element, what is true concerning the thermal bulb?


96. 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 thermostatic expansion valve sensing bulb should be attached where on the return line?


97. Expansion valve maintenance should include which of the following procedures?


98. Which statement about calibrating a newly installed thermostatic expansion valve is correct?


99. Which of the installation steps listed is necessary for the proper operation of the thermostatic expansion valve?


100. What maintenance may be carried out on a thermostatic expansion valve?


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