Refrigeration & AC - QMED

The correct answer is B) "2". The set point adjustment of the device shown in the illustration GS-RA-14 is made by rotating the component labeled "2". This is typically a knob or dial that allows the operator to adjust the desired set point or threshold for the device's operation. The other options are incorrect because: A) "1" is likely the sensor or input component, not the set point adjustment. C) "3" and D) "4" are likely other components of the device, but not the set point adjustment mechanism.

The correct answer is B. 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. This is because as the ambient temperature decreases, the head pressure in the refrigeration system also decreases. The fan cycling control pressure switch would then signal the multi-speed motor to reduce the fan speed to maintain the appropriate head pressure in the system. The other options are incorrect because: A) The fan would cycle off under high ambient conditions, not low; C) Multiple fan systems would increase the number of fans running under high ambient conditions, not low; and D) The fan speed would decrease under low, not high, ambient conditions.

The correct answer is C) "2" should be turned to further compress the spring. Turning "2" to further compress the spring will increase the operating head pressure of the refrigeration system. This is because the spring is responsible for maintaining the pressure in the system, and compressing it will raise the overall pressure. The other options are incorrect because rotating "4" to compress or relax the bellows would not directly affect the operating head pressure, and turning "2" to relax the spring would decrease the pressure rather than increase it.

The correct answer is B) Valves "2" and "5" both closed, along with valves "1" and "6" both cracked open off their backseats. This arrangement allows for simultaneous reading of the compressor suction and discharge pressures. With valves "2" and "5" closed, the gauge manifold set is isolated from the refrigerant system, but with valves "1" and "6" cracked open, the suction and discharge pressures can be read directly from the gauge manifold. The other options are incorrect because they either do not isolate the gauge manifold set from the system (A and C) or do not allow for pressure readings to be taken (D).

The correct answer is D. The illustration GS-RA-03 shows the correct hand valve configuration for monitoring both the low and high system pressures. Option D depicts the proper set-up, with the low-pressure gauge connected to the low-pressure port and the high-pressure gauge connected to the high-pressure port. This configuration allows the operator to independently monitor the pressures in both the low and high-pressure systems, which is a critical safety requirement for the proper functioning and maintenance of the overall system. The other options (A, B, and C) do not provide this dual pressure monitoring capability.

The correct answer is D. The reason D is the correct answer is that a halogen leak detector, such as a halogen leak detector, would be the appropriate choice for detecting leaks in a system pressurized with nitrogen. Halogen leak detectors are designed to detect the presence of halogen-based refrigerants, which are not affected by the type of pressurizing gas used in the system. The other options, A, B, and C, would not be suitable for this application, as they are designed for different types of leak detection, such as soap bubble testing or electronic leak detectors, which may not be effective for nitrogen-pressurized systems.

The correct answer is D) direct vapor recovery. The connection scheme shown in figure "B" of the illustrated self-contained recovery unit connection diagrams (GS-RA-33) supports a direct vapor recovery method. This means that the recovery system is designed to capture and recover the vapors directly from the container or vessel, without the use of a push-pull mechanism. Direct vapor recovery is a more efficient and environmentally friendly method compared to liquid recovery or push-pull vapor recovery, as it minimizes the potential for vapor emissions. The other answer choices are incorrect because they do not accurately describe the recovery method supported by the connection scheme depicted in the illustration.

The correct answer is B) X. The high-pressure cutout switch, also known as the high-pressure fuel cutoff switch, is typically labeled with the letter "X" in illustrations of marine engine systems. This switch is designed to automatically shut off the engine's fuel supply in the event of a high-pressure fuel system failure, preventing a potentially dangerous situation. The other options, A) W, C) Y, and D) Z, likely represent different components of the engine system, such as the fuel pump, fuel filter, or low-pressure fuel cutoff switch, but they do not specifically indicate the high-pressure cutout switch.

The correct answer is D. The valve described in the question, which features a Schrader core valve that is unseated by the core depressor of a hose fitting when attached, is commonly referred to as a Schrader valve. This type of valve is used to gain access to hermetic systems, such as refrigeration and air conditioning systems, in order to charge, evacuate, or test the system. The other answer choices (A, B, and C) do not specifically describe a Schrader valve, and therefore are not the correct answer to the question.

The correct answer is B. The gauge 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, is the Vacuum Gauge (B) in the illustration GS-RA-37. This type of vacuum gauge is commonly used in HVAC systems to verify proper system evacuation and dehydration prior to charging the system with refrigerant. It displays the achieved vacuum in incremental steps, such as 500 microns, 300 microns, 100 microns, etc., rather than providing a continuous readout. This allows technicians to easily confirm the system has reached the desired level of evacuation without the need for precise measurement. The other gauge options in the illustration are not designed for this specific purpose of measuring micron-level vacuums for system dehydration verification.

The correct answer is B. The expansion valve should not be adjusted, as the degree of superheat is within the accepted range. The coil temperature of 10°F and the low side pressure of 15 psig indicate that the system is operating within the normal range of superheat, which is typically between 6-12°F. Adjusting the expansion valve is not necessary in this case, as the system is functioning properly and the degree of superheat is appropriate. The other answer choices are incorrect because: A) a fouled liquid line strainer would not cause the low side pressure and superheat to be within the normal range; C) changing the filter drier would not directly affect the superheat; and D) cleaning the evaporator coils is not necessary if the superheat is within the acceptable range.

The correct answer is C) The expansion valve would hunt excessively, alternately starving and overfeeding the evaporator coil. If the replacement valve cage assembly is oversized at 5 tons compared to the original 1/2 ton rating, the expansion valve would not be able to properly control the refrigerant flow. The larger capacity valve cage would cause the expansion valve to constantly oscillate between starving and overfeeding the evaporator coil, resulting in excessive hunting behavior. This would lead to inconsistent superheat levels and poor system performance. The other options are incorrect because: A) The evaporator would not be starved, but rather would experience alternating starvation and overfeed conditions. B) The expansion valve would not function normally with the oversized valve cage. D) The evaporator would experience both insufficient and excessive superheat, not consistently insufficient superheat.

The correct answer is B. The key requirements for the evaporator coil are a 2 psi pressure drop, the need for externally adjustable superheat, and a replaceable power element. Based on the illustration, option B is the appropriate thermal expansion valve as it features an externally adjustable superheat and a replaceable power element, which meets the specified criteria. The other options would not be suitable - option A lacks the externally adjustable superheat feature, option C does not have a replaceable power element, and option D is not designed for the 2 psi pressure drop requirement.

The correct answer is B) The control bulb is located on the evaporator coil outlet. The thermostatic expansion valve regulates the flow of refrigerant into the evaporator coil based on the temperature of the refrigerant at the evaporator outlet. The control bulb, which senses the temperature, is located on the evaporator coil outlet to monitor the superheat of the refrigerant. This allows the expansion valve to adjust the refrigerant flow to maintain the proper amount of superheat, ensuring efficient operation of the refrigeration system. The other options are incorrect because: A) The thermostatic expansion valve does not directly regulate the temperature of the refrigerated space. C) The thermostatic expansion valve regulates superheat, not the solenoid valve. D) The external equalizing pipe is connected to the evaporator coil outlet, not the liquid receiver.

The correct answer is C) chill box thermostatic expansion valve. The valve labeled "29" in the illustration GS-RA-12 is the thermostatic expansion valve for the chill box evaporator in a multi-evaporator refrigeration system. The thermostatic expansion valve controls the flow of refrigerant into the chill box evaporator based on the temperature in the chill box, ensuring proper cooling. The other options are incorrect because: A) a freeze box would have a separate thermostatic expansion valve, B) a pressure regulating valve controls pressure, not temperature, and D) a solenoid valve is an on/off valve, not a metering valve like the thermostatic expansion valve.

The correct answer is B) thermostatic expansion valve. The thermostatic expansion valve is a component where flash gas formation is a normal occurrence. As the refrigerant passes through the thermostatic expansion valve, the sudden pressure drop causes some of the liquid refrigerant to vaporize, forming flash gas. This is a necessary part of the refrigeration cycle, as the flash gas is then drawn into the evaporator coil where it absorbs heat and completes the cooling process. The other options, such as the receiver tank, evaporator coil, and condenser coil, are not where flash gas formation would normally occur in the refrigeration system.

The correct answer is C. The expansion valve designed to maintain a constant evaporator pressure rather than a constant evaporator superheat is option C. This type of expansion valve is known as a pressure-regulating or pressure-limiting expansion valve. It is designed to maintain a specific evaporator pressure by automatically adjusting the refrigerant flow, which helps to prevent excessive pressure buildup in the system. The other options, A, B, and D, are typically used to maintain a constant superheat at the evaporator outlet, which is important for efficient system operation and to prevent liquid refrigerant from entering the compressor.

The correct answer is A) 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. This is the correct answer because, after the refrigerant has been recovered and any leaks repaired, the system needs to undergo a dehydration evacuation prior to recharging with refrigerant. To accomplish this, the vacuum pump suction manifold isolation valve should be opened, and the valves 1, 2, and 3 should be in the mid-position to allow the vacuum pump to evacuate the system. The low-side gauge manifold hand valve should be closed to prevent air from entering the system, while the high-side gauge manifold hand valve should be open to allow the vacuum pump to draw a vacuum on the entire system. The other options are incorrect because they do not properly position the valves to achieve a full system evacuation. Options B, C, and D do not have the correct valve positions to effectively evacuate the system.

The correct answer is A) the saturation temperature of the refrigerant that corresponds to the gauge pressure at the point of measurement. On a compound gauge for a refrigerant system, in addition to the indicated gauge pressure, the saturation temperature corresponding to that pressure is also displayed. This is because the saturation temperature is a critical piece of information needed to understand the state and behavior of the refrigerant in the system. The other options are incorrect because they do not represent the complete information provided on a compound gauge. Option B is incorrect as the gauge does not display metric pressure equivalents. Option C is incorrect as the gauge displays gauge pressure, not absolute pressure. Option D is incorrect as the gauge displays the saturation temperature, not the actual temperature of the refrigerant.

The correct answer is A) it senses compressor suction pressure and controls the quench valve. The pressure transducer shown in the illustration GS-RA-17 is used to sense the compressor suction pressure and control the quench valve. The quench valve is responsible for regulating the flow of refrigerant to the compressor, and the pressure transducer helps maintain the appropriate suction pressure by adjusting the quench valve as needed. The other options are incorrect because they do not accurately describe the function of the pressure transducer in this particular system. Option B and C mention the suction modulation valves, which are not part of the system depicted in the illustration. Option D refers to the compressor discharge pressure, which is not the parameter being monitored by the pressure transducer in this case.

The correct answer is C) prevent the entrance of air into the chiller when the chiller is idle. The pressure maintenance system shown in the illustration GS-RA-40 is designed to prevent the entrance of air into the chiller when the chiller is not in operation. This is important to maintain the system's integrity and prevent contamination of the refrigerant. When the chiller is idle, the pressure maintenance system uses a small pump to circulate the refrigerant and maintain a positive pressure, which prevents air from being drawn into the system. The other options are incorrect because they do not accurately describe the primary function of the pressure maintenance system in this context. Option A is incorrect as the system is not intended to maintain a low compression ratio under low heat load conditions. Option B is incorrect as the system is not intended to prevent air entrance under low heat load conditions specifically, but rather when the chiller is idle. Option D is incorrect as the system is not intended to prevent surging.

The correct answer is A) 150-190 psig. The key factors here are the refrigerant used (R-134a), the box temperature set point of -15°F, the return air temperature of 0°F, and the ambient air temperature of 90°F. With these conditions, the normal range of expected discharge pressures for an air-cooled refrigerated container unit using R-134a would be 150-190 psig. This is based on the typical discharge pressure ranges for an R-134a system operating under these temperature conditions. The other answer choices are incorrect because they either fall outside the normal operating range (B and D) or are too high (C) for the given scenario.

The correct answer is C) When checked with control power on and the thermistor probe connected into the circuit, the thermistor probe voltage drop should be 3.805 volts. This is correct because at a supply water temperature of 45°F, the thermistor probe's resistance will result in a voltage drop of 3.805 volts when the probe is connected into the circuit with control power on. The thermistor probe's resistance changes with temperature, and the chart provided illustrates the expected voltage drop at different temperatures. The other options are incorrect because option A assumes the probe is isolated, option B gives an incorrect voltage drop, and option D assumes the power is off, which would not provide the necessary voltage to measure the thermistor probe's resistance.

The correct answer is B) Valve "14" is the king solenoid, valve "28" is the chill box solenoid, and valve "36" is the freeze box solenoid. This is the correct answer because the illustration GS-RA-12 shows the layout and labeling of the various components in a refrigeration system, and the descriptions in the answer choices accurately match the labeled components. Specifically, valve "14" is identified as the king solenoid, valve "28" is the chill box solenoid, and valve "36" is the freeze box solenoid. The other options are incorrect because they do not correctly identify the functions of the labeled valves in the illustration. For example, option A incorrectly states that valves "28" and "36" are both chill box solenoids, and option C incorrectly states that valves "28" and "36" are both freeze box solenoids.

The correct answer is A) cooling mode. The key is that the actual box temperature of -18.0°C is higher than the microprocessor-controlled temperature setting of -28.9°C. This indicates that the cooling mode should be active in order to lower the box temperature down to the desired -28.9°C setting. The cooling mode will engage the refrigeration system to actively remove heat from the container and maintain the frozen cargo temperature. The other options are incorrect because: B) heating mode would be used to increase the temperature, which is not needed in this case; C) modulating cooling mode would be used to maintain a narrower temperature range, not the current wide gap; and D) air circulation mode alone would not actively cool the container to the set temperature.

The correct answer is B. The 2-position diverting hot gas bypass solenoid valve is most appropriately represented by option B in the illustration GS-RA-19. This type of valve is commonly used in electrically operated refrigeration systems to control the flow of hot refrigerant gas, diverting it as needed to bypass the condenser during certain operating conditions. The other options, A, C, and D, represent different valve types that may be used in refrigeration systems but are not specifically designed for the 2-position diverting hot gas bypass function required in this application.

The correct answer is C) the highest. When all four evaporators of a multi-box refrigeration system are actively being fed with liquid refrigerant, the control oil pressure acting on the hydraulic relay piston will be at its highest value. This is because the capacity controlled compressor needs to operate at its maximum capacity to meet the cooling demand of all four evaporators, which requires the highest control oil pressure to fully open the unloader mechanism and allow the compressor to run at its maximum output. The other options are incorrect because A) the lowest control oil pressure would not allow the compressor to meet the cooling demand, and B) the mid-range control oil pressure would not be sufficient to fully open the unloader mechanism. Option D is incorrect because the lube oil system is directly involved in the operation of the unloader mechanism, which controls the compressor's capacity.

The correct answer is D) discharge of the compressor lube oil pump. The fluid used as the source of actuating power against the underside of the unloader power element piston of the refrigeration compressor capacity control mechanism is obtained from the discharge of the compressor lube oil pump. This is because the lube oil pump is designed to provide pressurized oil to the various components of the compressor, including the capacity control mechanism, to ensure proper lubrication and operation. The other options are incorrect because A) a secondary hydraulic pump is not typically used for this purpose, B) the high side liquid receiver does not contain the necessary pressurized fluid, and C) the gas discharge from the compressor would not provide the required actuating power.

The correct answer is C) welded, fully hermetic. This is the correct answer because a fully hermetic refrigeration compressor has a welded casing that is not designed to be serviced. This type of compressor is sealed and not accessible for maintenance, which makes it a more reliable and durable design for marine applications where accessibility may be limited. The other options are incorrect - option A describes a semi-hermetic compressor that is designed to be serviced, option B refers to an open drive compressor which has an external drive mechanism, and option D describes an external-drive compressor which is not a fully integrated, hermetic design.

The correct answer is B) It automatically transitions the recovery unit from the direct liquid recovery mode to the direct vapor recovery mode. The purpose of the item labeled "FS2" in the illustrated flow diagram is to automatically switch the recovery unit from liquid recovery mode to vapor recovery mode as the refrigerant is being transferred from the high-pressure appliance. This transition is necessary to ensure the recovery process is conducted safely and efficiently, as per the EPA Clean Air Act regulations governing the recovery of refrigerants. The other answer choices are incorrect because they do not accurately describe the functional purpose of FS2 in this specific recovery unit design. The unit does not have a mechanism to automatically shut down the compressor based on the recovery cylinder fill level, discharge pressure, or vacuum depth.

The correct answer is B. Heat is removed from the refrigerant circulating through the refrigeration system by the condenser (component B). The condenser is the part of the refrigeration cycle where the hot, high-pressure refrigerant gas released by the compressor is cooled and condensed back into a liquid by transferring its heat to the surrounding air or cooling water. The other options are incorrect because: A) is the compressor, which applies pressure to the refrigerant gas to circulate it through the system. C) and D) are the expansion valve and evaporator, respectively, which are responsible for the cooling effect, not the heat removal.