Refrigeration Excellence
28. When the defrost cycle is terminated, the evaporator fans will A. Immediately come on B. Start on low speed and gradually increase speed C. Be energized by the head pressure control D. Delay coming on
D. Delay coming on
47. Expendable refrigerant means A. It is the most expensive refrigerants B. It cannot be released to the atmosphere C. It can only be recovered once D. It can be used one time
D. It can be used one time
23. The thermostatic expansion valve (TEV) maintains a constant _______ in the evaporator. A. Temperature B. Pressure C. Liquid level D. Superheat
D. Superheat
40. High temperature refrigeration applications normally provide box temperatures of A. 47°F to 60°F B. 28°F to 40°F C. 60°F to 75°F D. 30°F to 45°F
A. 47°F to 60°F
54. What type of oil is used with HFC refrigerant? A. Alkyl-benzene B. Mineral C. Flax seed D. Polyol Esther
A. Alkyl-benzene
53. When work on a refrigerator is complete, the compressor service valves should be in what position? A. Back seated B. Front seated C. Cracked D. Midpoint
A. Back seated
49. "Pump down" means to capture system refrigerant in the A. Recovery cylinder B. Compressor C. Condenser and/or liquid receiver D. Suction accumulator
C. Condenser and/or liquid receiver
51. The suction accumulator prevents flood back from which of the following? A. An undercharge of refrigerant B. An evaporator fan set too high C. Flooding after hot gas termination D. TXV bulb clamped too tight to the suction line
C. Flooding after hot gas termination
64. A severe evaporator freeze up may cause A. High discharge pressure B. High suction pressure C. Liquid flood back D. Damage to TXV
C. Liquid flood back
55. On an expansion valve refrigeration system, a low pressure control can indirectly be used for A. Overcharge protection B. High side cut out C. Control refrigerant flow rate D. Controlling box temperature
D. Controlling box temperature
13. A properly functioning condenser will first A. Condense, then de-superheat B. Sub-cool, then de-superheat C. Sub-cool, then superheat D. De-superheat, then sub-cool
D. De-superheat, then sub-cool
71. What pH level is considered neutral and desired for ice machine or cooling tower applications? A. 5 B. 7 C. 9 D. 10
B. 7
10. What time interval is required between each superheat adjustment? A. Not less than one hour B. About 10 to 15 minutes C. At least a half hour D. No time delay
B. About 10 to 15 minutes
77. At what evaporative temperature does an icemaker begin to make ice? A. 32°F B. 0°C C. 0°F D. 20°F
C. 0°F
91. If a pressure control has been adjusted to cut in at 40 psig, in order to have a 15 psig cut out, the differential setting of the control must be A. 55 B. 35 C. 25 D. 15
C. 25
29. An off-cycle defrost method is often used on evaporators operating at a minimum of A. 0°F B. 20°F C. 35°F D. 40°F
C. 35°F
94. Esther based oils are A. Aromatic blends B. Vegetable and origin C. A synthetic oil D. Naot a popular choice for retrofit
C. A synthetic oil
21. Multiple compressors provide A. Positive oil return B. Lower humidity and high humidity locales. C. Capacity control D. Zone control
C. Capacity control
68. The relationship between low side absolute pressure and high side absolute pressure is called A. Clearance pocket B. Compressor capacity C. Compression ratio D. Two-stage application
C. Compression ratio
58. What valve is used to control excessive pressure entering the compressor during a hot pull down? A. Head pressure regulator B. Evaporator pressure regulator (EPR) C. Crank case pressure regulator (CPR) D. Oil pressure regulator
C. Crank case pressure regulator (CPR)
99. The two manually adjust the parameters of a high-pressure switch are A. Spring tension and snap action B. Differential and cut out C. Cut in and cut out D. Differential and cut in
C. Cut in and cut out
61. A thermostatic expansion valve (TXV) that creates an unstable suction pressure is said to be A. Flashing B. Modulating C. Hunting D. Fractionating
C. Hunting
59. The oil return orifice inside a suction line accumulator is designed to A. Return oil only during the off cycle back to the compressor B. Maintain the same pressure in the evaporator to the inlet of the compressor C. Meter liquid refrigerant and oil at acceptable rate D. Equalize discharge and suction pressures during off cycle
C. Meter liquid refrigerant and oil at acceptable rate
37. The type of compressor that allows access to the internal components is the A. Hermetic B. Scroll C. Semi hermetic D. Rotary
C. Semi hermetic
52. When the compressor service valve is back seated, which port is closed? A. Outlet port B. Inlet port C. Service port D. Pilot port
C. Service port
63. Liquid slugging of the compressor can be caused by A. Low oil B. TXV hunting C. High superheat setting D. High ambient
B. TXV hunting
85. A restaurant owner has indicated that their walk in cooler is running above normal temperatures and seems to be running all the time. Upon initial visual inspection, the technician finds that all evaporator fans are running properly and the thermostat is calling for cooling. Further inspection reveals that the evaporator has a heavy accumulation of ice on the top of one third of the coil. Measuring the evaporator superheat, the technician finds that it is 22°. A check of system pressures indicates lower than normal suction and discharge pressures. A check of condenser subcooling shows 2°. The technician determines that A. The evaporator is flooded due to an overcharge of refrigerant B. The evaporator is starved due to a partial loss of refrigerant charge C. The evaporator is operating properly, but a defrost problem exists D. The TXV sensing bulb has probably lost its charge and must be replaced
B. The evaporator is starved due to a partial loss of refrigerant charge
84. A technician has performed a leak repair on a vending machine that uses a self-contained refrigeration system that employs a capillary to metering device. After repairing the leak, the filter dryer was replaced in the system was evacuated. The data plate calls for an 18 ounce refrigerant charge, which is carefully measured into the system. When the system is started, suction pressure, and head pressure are low. Motor amp draw is lower than normal, according to the manufacturer's specifications. Which of the following could cause of these low readings? A. There is too much oil in the system B. The replacement filter dryer is larger than the original C. Ambient temperature is 95°F D. Ambient temperature is 72°F
B. The replacement filter dryer is larger than the original
60. Why do suction line filter dryer's have two service ports? A. To help remove acid trapped in the dryer B. To enable checking pressure drop across the dryer C. One port is used for charging with liquid, the other is used for charging with vapor D. One port is used for adding oil, the other poor is used for adding vapor to the system
B. To enable checking pressure drop across the dryer
69. Capacity control of a large compressor can be performed with A. Solenoid valve B. Hand valves C. Unloaders D. Dampers
C. Unloaders
79. Defrosting a low temperature evaporated can be accomplished by A. Stopping the evaporator fan motor B. Reversing the compressor rotation C. Using electric heaters D. Installing a modulating valve
C. Using electric heaters
20. The major difference between a cooling tower and an evaporative condenser is A. Location based on prevailing winds in the angle of the sun B. The only real difference is design and operating controls of the water flow C. The refrigerant is cool directly in a cooling tower D. The refrigerant is indirectly cooled in the cooling tower
D. The refrigerant is indirectly cooled in the cooling tower
5. Superheat measurements are best taken A. During a hot pulldown B. At 8°F two 12°F C. During defrost D. With the system operating at design conditions
D. With the system operating at design conditions
42. Low temperature refrigeration applications, other than ice makers, will normally provide box temperatures of A. 0°F to 32°F B. 0°F to -20°F C. -10°F to 32°F D. -40°F to 0°F
A. 0°F to 32°F
8. Dry type evaporators operate most efficiently with the superheat setting of approximately A. 8°F to 12°F B. 13°F to 19°F C. 20°F to 30°F D. 31°F to 40°F
A. 8°F to 12°F
19. Parallel compressors often referred to as a rack system may use A. A common suction, but not a common discharge header B. A common discharge header, but not a comment section header C. Both comment section header and common discharge header D. A common accumulator, but never a common receiver
A. A common suction, but not a common discharge header
14. The effect of an inefficient water cooled condenser will A. Act the same as an air cooled condenser B. Act different than an air cooled condenser C. Always be mixed with incoming medium without being reheated D. Seldom be inefficient on commercial equipment
A. Act the same as an air cooled condenser
25. Some capillary tube systems take advantage of heat exchange by soldering the capillary tube to the suction line. In order to obtain the correct superheat reading, it must be taken A. After the capillary tube suction line heat exchanger B. Before the capillary tube suction line heat exchanger C. Before the suction line enters the compressor D. On the capillary tube as it enters the evaporator
A. After the capillary tube suction line heat exchanger
4. When measuring evaporator superheat on a commercial system that has a long suction line, the pressure reading should be taken at the A. Compressor inlet B. Evaporator outlet C. Condenser outlet D. Receiver Inlet
A. Compressor inlet
82. Which of the following determines the viscosity of refrigeration oils used in refrigeration systems? A. Condensing temperature and type of compressor B. Condenser temperature and evaporator temperature C. Evaporator temperature and type of compressor D. Evaporator temperature and refrigerant lines size
A. Condensing temperature and type of compressor
83. A custom reports that they're low temperature reach-in freezer had a burned out compressor replaced last week by another service company, and now is not cooling properly. When you arrive in exam in the system, you find that the evaporator seems to be starving for refrigerant. On inspecting the condensing unit, you noticed that the liquid line is sweating where it leaves the filter dryer. This is most likely the result of A. Debris from the burned compressor has clogged the filter dryer B. Air in the system C. Low refrigerant charge D. Refrigerant overcharge
A. Debris from the burned compressor has clogged the filter dryer
78. What device is used to check for parallel misalignment of a motor coupling? A. Dial indicator B. Alignment-Techno meter C. Level and precision ruler D. Caliper and parallel level
A. Dial indicator
2. The difference between the temperature of the refrigerant boiling in the evaporator and the temperature at the evaporator outlet is known as A. Evaporator superheat B. Latent heat C. Evaporator sub-cooling D. Sublimation
A. Evaporator superheat
7. A TXV with an external equalizer is used on A. Evaporators with a high pressure drop B. Evaporators with a low pressure drop C. High temperature application is only D. All evaporators
A. Evaporators with a high pressure drop
73. Which refrigerant line is most sensitive to improper sizing? A. Liquid line B. Suction line C. Discharge line D. Condensate line
A. Liquid line
32. An automatic pumpdown system requires a A. Liquid line solenoid B. Suction accumulator C. Thermostatic cut out D. Fan cycle switch
A. Liquid line solenoid
33. Short cycling in a pumpdown system is most likely caused by a leaking A. Liquid line solenoid valve B. TEV seat C. Suction line solenoid valve D. Cylinder unloading device
A. Liquid line solenoid valve
76. A string of five frozen food cases are operated by one compressor. All five cases are iced up. What is the likely problem? A. Low refrigerant charge B. Defective thermostat C. Plugged condensate drain D. Defective defrost timer
A. Low refrigerant charge
66. If an oil separator is not used, A. Oil traps should be installed in all vapor carrying lines B. The system should be charged with 1/2 quart more oil C. The system should be charged with 1/2 quart less oil D. The system should be charged with less refrigerant
A. Oil traps should be installed in all vapor carrying lines
1. In a dry type (direct expansion) evaporator, liquid refrigerant must boil away as close to the end of the coil as possible in order to: A. Operate at high-efficiency B. Ensure that Frost is not accumulate C. Subcool the compressor D. Ensure proper oil return
A. Operate at high-efficiency
18. Cooling towers that pass air over water to remove system heat are limited in capacity by A. Outside air wetbulb temperature B. Outside air dry bulb temperature C. Inside air wetbulb temperature D. Inside air dry bulb temperature
A. Outside air wetbulb temperature
9. An evaporator used to chill liquids is operating within normal superheat setting. But the system is not cooling the product properly. Which of the following is most likely the cause? A. Overcharge of refrigerant B. Undercharge of refrigerant C. The circulator D. The TXV
A. Overcharge of refrigerant
70. Vibration eliminator's should be installed _______ to the compressor crankshaft centerline. A. Perpendicular B. Parallel C. Vertical D. At a 90° angle
A. Perpendicular
90. And oil separator must be kept warm in order to A. Prevent sluggish return of the oil to the crankcase B. Prevent refrigerant from convincing in a separator during the off cycle. C. Keep the oil at the same temperature as the oil in the crankcase. D. Operate properly when exposed to low outdoor ambient.
A. Prevent sluggish return of the oil to the crankcase
36. The crankcase heater is used to prevent A. Refrigerant migration to the compressor crankcase during the off cycle B. High compressor superheat under low ambient conditions C. Prevent liquid flood back to the compressor D. Refrigerant migration to the compressor crankcase
A. Refrigerant migration to the compressor crankcase during the off cycle
96. The term "refrigerant conditions" refer to which of the following? A. Saturated, superheated, or sub cooled refrigerant B. Pressurized refrigerant only C. A system in a complete vacuum D. The outdoor ambient temperature
A. Saturated, superheated, or sub cooled refrigerant
27. A hot gas defrost cycle can be initiated by a A. Timer B. Defrost thermostat C. Pressure control D. Control thermostat
A. Timer
43. What is the purpose of an oil separator? A. To capture oil and prevent it from traveling throughout the system B. To clean the oil and separate the refrigerant from it C. To filter all of the oil leaving the evaporator D. To prevent evaporator freeze up
A. To capture oil and prevent it from traveling throughout the system
38. Low ambient temperatures seriously affect A. Water cooled units B. Air cooled units C. Compressors D. Dairy coolers
A. Water cooled units
15. The refrigerant condensing temperature in a water cooled condenser is normally about _____ higher than the leaving water. A. 5°F B. 10°F C. 15°F D. 20°F
B. 10°F
48. If a walk-in cooler requires a high percentage of moisture in the air due to the product being stored, the logical evaporator TD would be A. 10°F B. 20°F C. 30°F D. 40°F
B. 20°F
16. The refrigerant and an air cooled condenser will normally contends at approximately _____ higher temperature than the air passing over it. A. 10°F B. 30°F C. 75°F D. 100°F
B. 30°F
95. When measuring oil pressure on the compressor with a pressurized oiling system, A. Actual oil pressure can be read directly from the oil pressure gauge B. Actual oil pressure must be calculated by subtracting suction pressure from the oil pressure gauge reading C. Actual oil pressure must be calculated by adding suction pressure to the oil pressure gauge reading D. Actual oil pressure is not important because it is a pressurize system
B. Actual oil pressure must be calculated by subtracting suction pressure from the oil pressure gauge reading
97. A water regulating valve used to control water flow in a water cooled condenser application can be most accurately adjusted by A. Adjusting the valve to the manufacturers stated flow rate and PSI per minute B. Adjusting the valves to the design condensing temperature C. Adjusting the valve to the system low side pressure required for the application D. Adjusting the valve to the running load ampere draw of the compressor
B. Adjusting the valves to the design condensing temperature
44. Blended refrigerants should be charged into a running system A. As a vapor into the high side B. As a liquid through a throttling valve into the low side C. As a liquid through a throttling valve into the high side D. As a vapor into the low side
B. As a liquid through a throttling valve into the low side
50. What is the normal operating position for a compressor service valve? A. Front seated B. Back seated C. Cracked D. Closed
B. Back seated
45. A refrigeration system that uses the evaporator of the first stage to exchange heat with the condenser of the second stage refrigeration system is called a A. Piggyback system B. Cascade system C. Twin system D. Parallel system
B. Cascade system
80. A system that uses an automatic expansion valve (AEV) is not cooling enough and running continuously. The gauges reveal low head pressure, but the suction pressure is acceptable. This could be caused by A. Low refrigerant charge B. Defective valves in the compressor C. Refrigerant overcharge D. Product overload
B. Defective valves in the compressor
65. The oil separator is installed in the A. Suction line B. Discharge line C. Liquid line D. Hot gas bypass line
B. Discharge line
62. Head pressure control valves permit hot gas to travel directly to the A. Condenser B. Evaporator C. Liquid receiver D. TXV
B. Evaporator
56. What valve is used to connect multiple evaporators of different temperatures to a single compressor? A. Crank case pressure regulator (CPR) B. Evaporator pressure regulator (EPR) C. Oil pressure regulator D. Head pressure regulator
B. Evaporator pressure regulator (EPR)
57. What valve is used to prevent evaporator pressure from falling below a set limit? A. Crank case pressure regulator (CPR) B. Evaporator pressure regulator (EPR) C. Oil pressure regulator D. Head pressure regulator
B. Evaporator pressure regulator (EPR)
75. A Michigan service man is called a to a supermarket on a cold winter day because all the frozen food is melting. A low temperature rack of five compressors control the frozen food and ice cream units. Power supply is okay, but all compressors are off. All five low pressure controls are open. The liquid receiver shows full. The hot gas discharge line is cold because the condenser is on the roof. What is the likely cause of the trouble? A. A faulty liquid line service valve B. Faulty condenser ambient controls C. Defective pump down solenoid D. A plugged filter dryer
B. Faulty condenser ambient controls
35. The "low ambient control" is used to control A. Suction pressure B. Head pressure C. Evaporator fans D. Compressor
B. Head pressure
34. An evaporator pressure regulator valve (EPR valve) is a mechanical control that A. Controls compressor cycling B. Limits pressure setpoint in the evaporator C. Limits the pressure in setpoint of a thermostatic expansion valve (TXV). D. Is used with the capillary tube system to prevent high suction pressure
B. Limits pressure setpoint in the evaporator
81. Bubbles or foaming in the compressor's oil sightglass are an indication of A. A low oil level condition B. Liquid refrigerant in the oil C. Too much oil in the crankcase D. Moisture in the oil
B. Liquid refrigerant in the oil
22. A dirty evaporator and subsequent low evaporator pressures will cause A. High compression ratios B. Low compression ratios C. High head pressure D. High suction pressure
B. Low compression ratios
88. A customer calls it indicates that a walk-in freezer is running gradually higher box temperature. The technician finds the box at 15°F, the thermostat is set properly for a freezer application, and the condensing unit is operating, but not cycling after adequate pull down time. An inspection of the evaporator reveals heavy ice accumulated across the top two rows, and the entire body of the thermostatic expansion valve and power element frozen in a ball of ice. The technician decides to advance the electromechanical defrost timer to the next defrost. And observe the defrost function. In doing so, the evaporator defrosts to the level of the ice buildup, but no further. All power to both the freezer and condensing unit is removed, locking and tagging each disconnect. The technician then defrosts the remainder of the ice from the evaporator and expansion valve body. All evaporator housings are placed back and secured in their normal positions. Manifold gauges are connected to the server sports at the condensing unit. The locks and tags are removed, and the unit is started. After 15 minutes of run time, the system pressures indicate a starved evaporator. A check of evaporator superheat shows the system is undercharged. A thorough leak test is performed in the technician determines A. There is no leak, the ice that formed on the expansion valve power element caused a loss of refrigerant control and starved the evaporator. B. Over a period of time, moisture had gathered under the flare nut on the evaporator side of the expansion valve. Repeated freezing and thawing had created enough for us to damage the flare, creating a slow refrigerant leak. C. The system is a leak free. But the ice that formed on the evaporator and expansion valve caused excessive some cooling of the liquid refrigerant preventing the liquid from changing state as it would have under normal pressure drop conditions. D. The system is a leak free. But the defrost timer defrost. Needed to be extended an additional five minutes to adequately defrost the evaporator during each defrost cycle.
B. Over a period of time, moisture had gathered under the flare nut on the evaporator side of the expansion valve. Repeated freezing and thawing had created enough for us to damage the flare, creating a slow refrigerant leak.
30. Excessive frost on the evaporator causes A. Increased efficiency B. Reduced heat transfer C. High humidity D. Increased superheat
B. Reduced heat transfer
24. What type of ice is made with the commercial icemaker that uses a gear motor and auger? A. Crescent cube ice B. Shaved ice C. Cell type of ice D. Block ice
B. Shaved ice
87. A customer complains that their countertop ice machine is making a loud noise and not producing any ice. Upon arrival, the technician removes the front panel and determines that the noises coming from the ice machine auger. Before the technician can unplug the power supply, the auger drive motor overload opens in the drive motor stops. The machine's compressor continues to operate. The technician unplugs the ice machine and attach his gauges to the low and high side service ports. In addition, a clamp on ammeter is placed on the power lead to the compressor. The technician turns the power switch to the off position and plugs the ice machine back into the power supply. The technician locates the manual reset switch located on top of the auger drive motor and attempt to reset the switch. The switch will not reset and the motor frame is very hot. Using ice from another machine in the heavy plastic bag, the motor is cool enough for the switch to reset. The technician turns on the power switch and the auger drive motor, compressor, and condenser fan motor all start. After a few minutes of run time, the auger motor begins to make noise, but not as loud as before. The low side pressure begins to drop in falls below normal about the same time as the noise begins. The high side pressure is slightly lower than the normal for the ambient and the compressor begins to draw less current. Moving the ammeter to the auger drive motor shows the current rising to the upper limit of the RLA stated on the motor plate. The technician cuts off the power to the unit, checks the water reservoir, and finds that there is only a small amount of water present. The technician determines A. The bearings for the auger motor must be seized up causing the noise, and the additional load on the motor resulted in high current draw, which open the motor overload. B. The system has an under charge of refrigerant and is causing the lower than normal pressure readings. The lower pressures result in harder ice being formed and freezing the auger in the housing. This accounts for the motor heating up and tripping the overload. C. The lack of water flow reduced evaporator load, which resulted in the auger freezing up and the drive motor tripping the overload. The lower pressures and current are the result of low load on the evaporator. Waterflow must be restored and machine should operate properly. D. The gearbox is binding, probably due to a damaged drive gear. This results in the auger drive motor overheating. The auger is moving much slower than normal and not pulling in water at the base of the auger/evaporator assembly.
C. The lack of water flow reduced evaporator load, which resulted in the auger freezing up and the drive motor tripping the overload. The lower pressures and current are the result of low load on the evaporator. Waterflow must be restored and machine should operate properly.
100. The term "cryogenics" refers to refrigeration systems operating at what temperature range? A. 0°F to -35°F B. -40°F to -75°F C. -100°F to -175°F D. -250°F to -450°F
D. -250°F to -450°F
41. Medium temperature refrigeration applications will normally provide box temperatures of A. 20°F to 40°F B. 25°F to 42°F C. 28°F to 40°F D. 30°F to 42°F
D. 30°F to 42°F
6. A technician is checking the superheat on a multi circuit evaporator and finds one of the circuits has a superheat that is higher than the others. This could be caused by A. A dirty coil B. A refrigerant overcharge C. Uneven air distribution D. A blocked distributor
D. A blocked distributor
3. An expansion device that is stuck open will cause A. Low suction pressure B. A starved evaporator C. Excessive superheat D. A flooded evaporator
D. A flooded evaporator
72. On a rack of multiple compressors, each compressor is controlled by A. Suction pressure transducer B. Thermostat C. Interstage pressure D. CPR valve
D. CPR valve
26. A ______ is usually required for ultra low temperature applications. A. Cooler B. Comfort cooling system C. Freezer D. Cascade system
D. Cascade system
98. An oil pressure differential switch utilizes which of the following pressures in opening the context of the time delay heater? A. System suction and discharge pressures B. Sensing bulb and suction pressure C. Sensing bulb and discharge pressure D. Compressor crankcase pressure and oil pump discharge pressure
D. Compressor crankcase pressure and oil pump discharge pressure
92. Should liquid refrigerant accumulate in the oil separator, it will be returned to the crankcase with the oil. If this occurs, it will result in A. A stalled compressor due to excess vapor pressure in the crankcase B. Raising the oil level in the crankcase to a dangerous level C. Increased temperature of compressor components D. Dilution of the oil and filming in the crankcase
D. Dilution of the oil and filming in the crankcase
67. If a system has a long suction line riser, an oil trap should be installed A. Every 6 inches of vertical rise B. At the top of the riser C. Downstream of the accumulator D. Every 15 to 20 feet of vertical rise
D. Every 15 to 20 feet of vertical rise
93. When retrofitting a CFC/mineral oil system to an HFC based refrigerant A. Changing to another type of oil is not required B. You must add an alkyl-benzene oil C. You must add a napthenic oil D. Extensive oil flushing is required
D. Extensive oil flushing is required
17. Workable head pressure during periods of low ambient temperature can be achieved by using A. An economizer B. Evaporator dampers C. Evaporator flooding D. Fan cycle control
D. Fan cycle control
12. Some special applications use a flooded evaporator (operated full of refrigerant) in order to maintain the proper level of liquid refrigerant, a ______ type devices used. A. High side float B. Capillary tube C. AEV D. Low side float
D. Low side float
31. Automatic pump down systems are used to prevent A. Power surges on-demand utility systems B. Surges of liquid refrigerant (slugging) during shutdown C. Oil foaming at shutdown D. Migration of refrigerant to the crankcase during off cycles
D. Migration of refrigerant to the crankcase during off cycles
11. A low temperature evaporator used for cooling space or product refrigeration A. Is the same as one used for medium or high temperatures B. Must have fins space closer together C. Must be frosted periodically D. Must be defrosted periodically
D. Must be defrosted periodically
39. Water cooling towers require a periodic blow down to control A. Rainwater B. PH level above 20 C. Water overflow D. Scaling
D. Scaling
74. What is the most likely cause of the following symptoms? The compressor shuts off on the oil pressure switch. The oil sightglass is one half full. Suction pressure is 3 psig (R-502). A. Defective oil pump B. Insufficient oil C. Defective oil pressure switch D. Suction pressure too low
D. Suction pressure too low
86. A customer calls and indicates that he has a walk-in freezer that is cutting on and off after a very short run time on a repeated basis. He indicates that he had a higher than normal power bill the previous month and thinks that the unit's erratic behavior may have contributed to the higher bill. The technician arrives in inspects the freezer. The freezer box temperature is -10°F, and the condensing unit is off. However, the technician observes the condensing unit operate and short cycle several times within a few minutes of the demand being satisfied. The technician shut the unit down, blocking and tagging the disconnect. This system is equipped with both low and high pressure switches, a suction line accumulator, and a liquid line solenoid. The technician notices that there is ice buildup from the outlet of the liquid line solenoid to the expansion valve. Manifold gauges are attached to the service ports. Removing the lock in tag for the disconnect, the technician starts the system. The system pulls down to the thermostat setting with both the low and high side pressures normal for the application and refrigerant being used. The technician here's the audible click of the liquid line solenoid as the thermostat is satisfied in the condensing unit continues to run until the low pressure switch is cycles the unit off. Again the unit repeats the short cycling condition. The technician determines that A. The low pressure switch is Miss adjusted in the differential is too narrow B. The thermostat is defective and is closing after the box temperature rises 2°F C. The liquid line solenoid is leaking during the off cycle, causing the low pressure switch to cycle the condensing unit. D. The accumulator contains liquid refrigerant and the surrounding temperature vaporizes the liquid, causing the low pressure switch to close prematurely
D. The accumulator contains liquid refrigerant and the surrounding temperature vaporizes the liquid, causing the low pressure switch to close prematurely
89. A customer is experiencing low ice production in a cube type ice machine. Symptoms include long run cycle, thin or smaller cubes, and low production. The initial visual inspection confirmed the owners complaint of thin ice in the production. Further inspection reveals that the ice machine is equipped with a harvest solenoid and a thermostatic expansion valve. The water pump is operating in the water reservoir is clean and free of debris. A check of the water temperature in the reservoir is 32°F. The technician decides to install manifold gauges and checked system pressures. This indicates slightly elevated suction pressure with the discharge pressure at or near normal for the application and refrigerant used. A check of evaporator superheat shows it to be 15°F to 18°F. A check of temperature difference across the harvest solenoid indicates a temperature rise of approximately 10°F. A check of condenser subcooling indicates 15°F the technician determines that A. System is under charge and must be topped off to correct the problem. B. The thermostatic expansion valve is in properly adjusted and is not keeping the evaporator superheat within the normal range. C. Non-condensables are present in the system. The refrigerant must be recovered, the filter dryer changed, this is to be evacuated, and we charge by weight. D. The harvest solenoid is leaking, keeping the suction pressure above normal, and must be replaced.
D. The harvest solenoid is leaking, keeping the suction pressure above normal, and must be replaced.
46. To achieve peak efficiency and performance in a capillary tube system, A. Attach an auxiliary heat exchanger to the liquid line to provide extra flash gas B. Solder the capillary tube to the liquid line C. Remove 5 inches of insulation from the suction line D. The system must be critically charged
D. The system must be critically charged
