Refrigeration-Air Conditioning
52. The set point adjustment of the device shown in the illustration is made by rotating what component? Illustration GS-RA-14
"2"
53. 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 GS-RA-14
"2" should be turned to further compress the spring
30. 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 and other related class I or class II substances may result in fines for each violation per day of what amount?
$25,000
43.A refrigeration compressor used in a multi-box refrigeration system is designed with six of its eight cylinders able to be controlled for variable load conditions. If all of the reefer boxes are currently feeding, what percentage of the total number of compressor cylinders will be loaded after start up?
100%
97. 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 vacuum would be associated with the BEST chance of achieving a dehydration evacuation with a deep vacuum pump? Illustration GS-RA-56
29.99" Hg or 254 microns of Hg absolute
93. 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 before it comes into contact with the cooling coil? Illustration GS-RA-22
70 degrees F
11. 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
80 degrees F
73. Which of the following dehydrators or combination filter/driers features a core that can be replaced when the desiccant becomes saturated with moisture? Illustration GS-RA-10
A
96. Which of the following methods is normally used to control the circulated air temperature of an air conditioning system using chilled water circulation?
A regulating valve controls the quantity of chilled water flowing in the cooling coils.
13. Heat is removed from the refrigerant circulating through the refrigeration system, shown in the illustration, by which component? Illustration GS-RA-12
B
27. Which of the illustrated devices would be the LEAST accurate for the purposes of weighing-in a refrigerant charge? Illustration GS-RA-45
C
29. Which of the following illustrated expansion valves is designed to maintain a constant evaporator pressure rather than a constant evaporator superheat? Illustration GS-RA-24
C
62. Which lettered component, shown in the illustration, indicates the location of the receiver? Illustration GS-RA-12
C
87. For the proper control of the air temperature in an air conditioning system using chilled water circulation, which of the listed conditions should remain constant regardless of load changes?
Chilled water system supply temperature.
95. 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 system?
Cooling the air to a point below dew point, then reheating it.
6. 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?
Crankcase pressure regulator
24. Which of the illustrated valves is used to gain access to a hermetic system and features a Schrader core valve which is unseated by the core depressor of hose fitting when attached? Illustration GS-RA-69
D
71. The device shown in the illustration which is used for removing moisture from the liquid refrigerant in the system is labeled with what letter? Illustration GS-RA-12
E
61. Hard drawn copper tubing is commonly used in larger refrigeration systems. What statement concerning its use is true?
Hard drawn copper tubing is not easily flared, bent, or swaged, so brazed fittings are commonly used.
83. Which of the valves listed is normally closed when charging the refrigeration system through the high side?
Liquid line king valve
72. Which of the devices listed will indicate whether or not a refrigeration system's dehydrator continues to be capable of removing moisture from the circulating refrigerant?
Liquid line moisture indicating sight glass
18. A small obstruction at the thermostatic expansion valve inlet will result in which of the following conditions?
Lower than normal suction pressure.
1. When repairing a refrigeration system, a swaging tool set would be used to carry out which of the following operations?
Swaging tools can be used to expand an end of one tube to fit onto a tube of the same original outside diameter.
16. 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?
TXV hunting
92. 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 spaces? Illustration GS-RA-09
The dry bulb room temperature is controlled by a steam heated reheater and its associated pneumatic control valve.
91. Which of the following is true concerning the class "D" air conditioning system shown in the following illustration? Illustration GS-RA-42
The duct thermostat determines the amount of water flow circulating through the cooling coil.
21. 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 1/2 tons, what would be the result if the replacement valve cage was oversized at 5 tons? Illustration GS-RA-07
The expansion valve would hunt excessively, alternately starving and overfeeding the evaporator coil.
84. 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 refrigeration system? Illustration GS-RA-01
The hose labeled "H" should be connected to the suction service valve service port, the hose labeled "J" should be connected to the vapor valve on the refrigerant cylinder and the valve labeled "G" should be open.
20. Which of the following conditions will occur if the power element of the thermostatic expansion valve shown in the illustration loses its charge? Illustration GS RA-07
The valve will fail closed, providing no cooling capacity.
66. In a low-pressure centrifugal chiller, what is meant by the term 'high efficiency purge unit?'
Those purge units which discharge very little refrigerant with the air being removed.
32. Persons recovering refrigerant from small appliances must be certified as what type of technician under the EPA Clean Air Act rules?
Type I or Universal technician
86. After the refrigerant has been recovered, leaks repaired if necessary, the system ideally should undergo a dehydration evacuation prior to recharging with refrigerant. As shown in the illustration, besides the vacuum pump suction manifold isolation valve being opened, what would be the proper valve positions to accomplish and prove the evacuation? Illustration GS-RA-51
Valves 1, 2, and 3 should be in the mid-position and the low-side gauge manifold hand valve should be closed, and the high-side gauge manifold hand valve should be open.
94. Concerning the arrangement of equipment and associated hoses shown in the illustration, what statement is true? Illustration GS-RA-59
When recovering refrigerant from the centrifugal chiller using this method, it is possible to achieve the recovery levels required by law without any further recovery.
49. As shown in the illustrated refrigeration system piping schematic diagram with the various accessories and controls and equipped with an air-cooled condenser with high side pressure controls, what statement is true concerning the fan cycling control pressure switch? Illustration GS-RA-39
With a condenser fitted with a single fan driven by a multi-speed electric motor, the fan speed would decrease under low ambient temperature conditions.
4. Which of the lettered components shown in the illustration indicates the high-pressure cutout? Illustration GS-RA-12
X
33. What would be an example of a small appliance as defined in the EPA Clean Air Act rules?
a hermetically sealed water cooler with a 2 lb. refrigerant charge
76. Standard filter/driers used in many commercial type refrigeration units may contain what type of substance?
activated alumina or silica gel desiccant beads
90. To prevent the unnecessary loading of an air conditioning system while maintaining the designed dry bulb temperature and relative humidity in an air conditioning system, what should be done?
admit only enough fresh outside air to provide proper ventilation
68. For most multi-box refrigeration systems, the refrigerant sight glass would be located where in the system?
after the receiver in the liquid line
45. Capacity control of a centrifugal refrigeration compressor can be accomplished by what means?
all of the above
31. All shipboard personnel responsible for the maintenance and repair of air conditioning systems using refrigerants covered under the EPA Clean Air Act venting prohibition, must be certified through an approved Environmental Protection Agency (EPA) program to do which of the following?
before performing maintenance, service or repair that could reasonably be expected to release Class 1 or Class 2 refrigerants into the atmosphere
98. 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 initiate the test?
close the 'king' valve
41. 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?
closed until the motor is connected across the line at full voltage and current drawn is below full load current
80. In the illustrated refrigeration system, what is the proper name for the component labeled "A"? Illustration GS-RA-12
compressor
14. Sea water or low temperature central fresh water is typically provided to a ship's stores refrigeration plant for what purpose?
condense the refrigerant gas
88. In an air conditioning system, moisture is removed from the air by what means?
cooling coils
65. Loss of refrigerant during the process of purging of air and non-condensable gases can be kept to a minimum by what action?
cracking the purge valve briefly and allowing the refrigerant to re-settle between purges
75. Moisture is removed from a refrigeration system by what action?
cutting in the dehydrator
81. A device used to hold open the refrigeration compressor suction valve during starting to reduce the compression load is called what?
cylinder unloader
77. In a refrigeration system, silica gel is found in what component?
dehydrator or combination filter/drier
51. An arrow stamped on the valve body of a water regulating valve indicates which of the following?
direction of the flow
36. When installing a mechanical shaft seal on a refrigeration compressor, extreme care must be taken to prevent what from happening?
dirt and foreign particles from coming in contact with the highly polished sealing surfaces
42. The fluid used as a source of actuating power against the underside of the unloader power element piston of the refrigeration compressor capacity control mechanism illustrated is obtained from where? Illustration GS-RA-13
discharge of the compressor lube oil pump
34. 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 psig, what must be done?
do not attempt to recover any refrigerant and repair the leak before pulling a vacuum on the system
9. In a two stage centrifugal air conditioning system, the liquid refrigerant passes through the condenser directly to what component?
economizer
17. Moisture entering a typical refrigeration system will most likely produce what effect?
freeze in the expansion valve
19. An obstructed expansion valve may be indicated by an incompletely cooled evaporator and what other symptom?
frosting at the evaporator inlet
50. In a refrigeration system, the valve shown in the illustration is used for what purpose? Illustration GS-RA-14
head pressure regulating valve
47. Minor repairs may be performed on low-pressure refrigerant systems without recovering the refrigerant charge if the pressure in the system is raised to atmospheric. How may this be accomplished?
heat the refrigerant
78. The safety heads of most large reciprocating compressors used in refrigeration systems are held in place by what means?
heavy coil springs
69. A liquid indicator sight glass is useful in determining whether or not a refrigeration system is sufficiently charged. Where is it generally located in the system?
high-pressure liquid line
60. The receiver used in a refrigeration system performs what essential function?
holds the entire refrigerant charge after system pump down
59. What is the purpose of the pressure transducer as shown in the illustration? Illustration GS-RA-17
it senses compressor suction pressure and controls the quench valve
56. In a large refrigeration system having more than one evaporator, a king solenoid valve should be installed in what location?
just after the receiver
48. The most cost-effective method of recovering refrigerant from a low-pressure chiller with more than 500 lbs. of refrigerant and to meet EPA requirements is to recover the refrigerant using what protocol?
liquid recovery using a liquid pump, followed by vapor recovery using a vacuum pump based recovery unit
89. 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 means?
lowering the cooling coil temperature and raising the reheater temperature
39. In addition to the drive belt itself, a V-belt that is tensioned too tight will cause excessive wear to what other drive component?
motor shaft and compressor main bearings
5. The rupture disc on a low-pressure centrifugal refrigeration unit is used as an overpressure 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?
on top of chiller evaporator shell
57. Refrigeration system isolation valves are specially designed with a backseat, as well as a front seat. For what purpose are these valves designed in this way?
permit repacking the valve stem under pressure without shutting down
10. In an air conditioning system, what is the name of the chamber where the duct-work originates?
plenum chamber
35. Excessively tight drive belts installed between a motor and a refrigeration compressor pulley may cause what condition?
premature wear of both the pulley end motor shaft bearing and the pulley end compressor crankshaft main bearing due to overloading
70. Why are dehydrators usually located in the liquid line of refrigeration systems?
prevent icing of the expansion valve
8. What is one benefit of maintenance of proper air circulation in an air conditioned cargo space?
reduced slime and mold
100. The compressor used in a water-cooled air conditioning system is short cycling. A service check determines that the suction pressure remains above the normal cut-in point during cycling and that the discharge pressure rapidly builds up to the cut-out point while running and gradually falls to the cut-in point during the off cycle. What is likely the cause?
reduction in condenser water flow (scaled condenser)
38. When one belt of a multiple V-belt drive requires replacing, what will be required?
replace the entire belt set
7. A reheater in an air conditioning system performs what function?
restores the conditioned air temperature to a comfortable level
15. Zinc plates commonly found in refrigeration systems and used as sacrificial anodes are located where?
salt water side of the condenser
55. In addition to pressure, most compound and standard pressure gauges used for refrigeration service are also provided with a scale indicating what parameter?
saturated refrigerant temperature
79. The carbon seal ring of a refrigeration compressor crankshaft mechanical seal is held in position against the stationary ring face by using what device?
spring
63. In a refrigeration plant, what is one vital purpose of the receiver?
store the refrigerant charge
46. Why is a purge recovery unit typically fitted on low-pressure centrifugal chillers?
such a chiller can operate at a pressure below atmospheric pressure on the low side thus drawing in air through any low side leaks
3. When the relief valve opens on a refrigeration compressor discharge line, it discharges high-pressure refrigerant vapor to what location?
suction side of the compressor
2. 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?
the compressor will shut down by the action of the high-pressure cutout switch
44. During operating periods of a multi-box refrigeration system using a capacity controlled compressor, when all of the evaporators of a four box plant are actively being fed with liquid refrigerant, the control oil pressure acting on the hydraulic relay piston will be at what value?
the highest
37. If the discharge reed valves used in a refrigeration compressor are leaking badly, what statement is true?
the reed valves should be replaced
85. 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 done?
the refrigerant should be charged into the system as a vapor
12. In general, the thermal bulb for a thermal expansion valve used in a reciprocating air conditioning system is usually charged with what substance?
the same refrigerant as the system
58. In addition to the indicated gauge pressure, what other information is presented on the compound gauge for the hypothetical refrigerant illustrated? Illustration GS-RA-16
the saturation temperature of the refrigerant that corresponds to the gauge pressure at the point of measurement
22. If the superheat value of the thermostatic expansion valve is adjusted too high, what would be the result?
the suction line of the compressor will be abnormally warm
23. 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?
the suction line will be abnormally cold and liquid may flood back to the compressor
64. In a refrigeration system, from what location would air and non-condensable gases be removed?
the top of the condenser purge connection
40. 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?
the valve will further close, raising evaporator pressure and lowering suction pressure
74. 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)?
thermal expansion valves
26. Before charging a refrigeration unit, unless quick disconnect fittings are used, the refrigerant charging hoses should be prepared in what way?
they should be purged with refrigerant
67. During normal operation, traditionally, how has most of the refrigerant released to the atmosphere from low-pressure systems?
through the purge unit vent
54. 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
to the line connected to the evaporator outlet
99. When recovering the remaining R-134a refrigerant from the centrifugal chiller shown in the illustration as a vapor using the recovery unit's compressor, in addition to opening valves "1a", "1b", and the compressor suction and discharge isolation valves, which of the following would be the correct valve lineup? Illustration GS-RA-28
valves "3", "4", and "6" open; valves "2", "5", "7", "8", and "10" closed
25. How should small appliances with less than three pounds of refrigerant be charged with refrigerant?
vapor charged
82. What is the drive arrangement of refrigeration compressor shown in figure "B" of the illustration? Illustration GS-RA-41
welded, fully hermetic
28. Concerning the charging of refrigerant into a vapor compression refrigerating system, which of the following is true?
when charging as a liquid it should be to the high side only
