Pass Benchmark: 70% (21/30) • Standard: USCG NMC / 46 CFR
USCG Refrigeration & Air Conditioning (Set 18)
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Question 1 of 30
A high-pressure centrifugal chiller currently charged with R-134a is being evaluated for the need for leak testing. Using the leak test procedures decision tree illustrated and the R-134a pressure-temperature chart illustrated, with the machine idle and the pressures equalized at 10 psig with an ambient temperature of 60°F, what statement is true? Illustration GS-RA-47 Illustration GS-RA-47: the U.S. Coast Guard has not released this illustration.
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30 MCQs #1 A high-pressure centrifugal chiller currently charged with R-134a is being evaluated for the need for leak testing. Using the leak test procedures decision tree illustrated and the R-134a pressure-temperature chart illustrated, with the machine idle and the pressures equalized at 10 psig with an ambient temperature of 60°F, what statement is true? Illustration GS-RA-47
Illustration GS-RA-47: the U.S. Coast Guard has not released this illustration. #2 If a refrigeration compressor were short cycling on the low-pressure cutout switch, what is the most probable cause? #3 As shown in figure "B" of the illustrated self-contained recovery unit connection diagrams, what is the recovery method supported by the connection scheme? Illustration GS-RA-33
Illustration GS-RA-33: the U.S. Coast Guard has not released this illustration. #4 What is the correct color-coding of refrigerant recovery cylinders regardless of the refrigerant contained within? #5 What must be done, at a minimum, before a system can legally be opened up for repairs while adhering to the prohibition against the venting of halogenated fluorocarbon refrigerants to the atmosphere? #6 Which of the following substances is normally classified as a low-pressure refrigerant? #7 What is the color-coding for a storage container of R-134a refrigerant? #8 Alkyl benzene ISO 32 cSt synthetic refrigerant oil is miscible and suitable to use with which of the following refrigerants? #9 The pressure in the part of a high-pressure refrigeration system about to be opened for a non-major repair should be brought to what value? #10 You are checking the supply chilled water temperature thermistor probe on a high-pressure hermetic centrifugal chiller. Using the illustrated chart, what statement is true if the supply water temperature is verified 45°F with a digital thermometer? Illustration GS-RA-48
Illustration GS-RA-48: the U.S. Coast Guard has not released this illustration. #11 Which of the following illustrated thermal expansion valves would be appropriate to use on an evaporator coil with a 2 psi pressure drop, where externally adjustable superheat and a replaceable power element are both desired? Illustration GS-RA-06 #12 Through which of the components shown in the illustration is flash gas formation a normal occurrence? Illustration GS-RA-25
Illustration GS-RA-25: the U.S. Coast Guard has not released this illustration. #13 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
Illustration GS-RA-24: the U.S. Coast Guard has not released this illustration. #14 In the multi-evaporator refrigeration system shown in the illustration, what is the proper name for the valve labeled "29"? Illustration GS-RA-12
Illustration GS-RA-12: the U.S. Coast Guard has not released this illustration. #15 An air-cooled refrigerated container unit using R-134a as a refrigerant has a box temperature set point of -15°F, but it is currently operating with a stable return air temperature of 0°F. The fresh air makeup vent is closed, the unit is operating at 460 VAC/60 Hz, and the unit is in full capacity cool (modulating valve 100% open). Using the illustrated troubleshooting guide, what would be the normal range of expected discharge pressures if the ambient air temperature is 90°F? Illustration GS-RA-52
Illustration GS-RA-52: the U.S. Coast Guard has not released this illustration. #16 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? #17 Which of the following statements is true concerning the illustrated gauge manifold set? Illustration GS-RA-01 #18 Which of the following statements is true concerning the gauge labeled "A" of the illustrated gauge manifold set? Illustration GS-RA-01 #19 Which of the illustrated gauges is capable of measuring vacuums at the micron level for the purpose of proving system dehydration during system evacuation with a vacuum pump, but displays the achieved vacuums at incremental threshold intervals rather than continuously? Illustration GS-RA-37 #20 In the presence of an open flame or hot surfaces, chlorinated fluorocarbon refrigerants decompose and form what chemical substance? #21 A container unit's microprocessor-controlled temperature controller is set at -28.9°C, appropriate for a frozen cargo of ice cream. In this mode of operation, according to the illustrated temperature controller functional diagrams, what should be the operational status of the unit if the actual box temperature is -18.0°C? Illustration GS-RA-035
Illustration GS-RA-035: the U.S. Coast Guard has not released this illustration. #22 Which of the following statements is true? Illustration GS-RA-12
Illustration GS-RA-12: the U.S. Coast Guard has not released this illustration. #23 What is the purpose of the low-pressure cut-out switch as used as a primary controller for a refrigeration system or unit? #24 A box solenoid valve used in a multi-box refrigeration system is operated by electromagnetic action by what control device? #25 Which of the following electrically operated refrigeration system valves would be most appropriate for use as a 2 position diverting hot gas bypass solenoid valve? Illustration GS-RA-19
Illustration GS-RA-19: the U.S. Coast Guard has not released this illustration. #26 When checking zinc plates or pencil zincs in the refrigerating system condenser, what should you do? #27 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
Illustration GS-RA-13: the U.S. Coast Guard has not released this illustration. #28 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? Illustration GS-RA-13
Illustration GS-RA-13: the U.S. Coast Guard has not released this illustration. #29 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? #30 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
Illustration GS-RA-39: the U.S. Coast Guard has not released this illustration.
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