LATEST UPDATED ESCO Light Commercial Refrigeration ACTUAL EXAM with Solutions., Exams of Refrigeration and Air Conditioning

Download LATEST UPDATED ESCO Light Commercial Refrigeration ACTUAL EXAM with Solutions. and more Exams Refrigeration and Air Conditioning in PDF only on Docsity! LATEST UPDATED ESCO Light Commercial Refrigeration ACTUAL EXAM with Solutions. 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 - Solution A. Operate at high-efficiency 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 - Solution A. Evaporator superheat 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 - Solution D. A flooded evaporator 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 - Solution A. Compressor inlet 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 - Solution D. With the system operating at design conditions 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 - Solution D. A blocked distributor 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 - Solution A. Evaporators with a high pressure drop 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 - Solution A. 8°F to 12°F 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 - Solution A. Overcharge of refrigerant 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 - Solution B. About 10 to 15 minutes 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 23. The thermostatic expansion valve (TEV) maintains a constant _______ in the evaporator. A. Temperature B. Pressure C. Liquid level D. Superheat - Solution D. Superheat 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 - Solution B. Shaved ice 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 - Solution A. After the capillary tube suction line heat exchanger 26. A ______ is usually required for ultra low temperature applications. A. Cooler B. Comfort cooling system C. Freezer D. Cascade system - Solution D. Cascade system 27. A hot gas defrost cycle can be initiated by a A. Timer B. Defrost thermostat C. Pressure control D. Control thermostat - Solution A. Timer 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 - Solution D. Delay coming on 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 - Solution C. 35°F 30. Excessive frost on the evaporator causes A. Increased efficiency B. Reduced heat transfer C. High humidity D. Increased superheat - Solution B. Reduced heat transfer 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 - Solution D. Migration of refrigerant to the crankcase during off cycles 32. An automatic pumpdown system requires a A. Liquid line solenoid B. Suction accumulator C. Thermostatic cut out D. Fan cycle switch - Solution 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 - Solution A. Liquid line solenoid valve 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 - Solution B. Limits pressure setpoint in the evaporator 35. The "low ambient control" is used to control A. Suction pressure B. Head pressure C. Evaporator fans D. Compressor - Solution B. Head pressure 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 - Solution A. Refrigerant migration to the compressor crankcase during the off cycle 37. The type of compressor that allows access to the internal components is the A. Hermetic B. Scroll C. Semi hermetic D. Rotary - Solution C. Semi hermetic 38. Low ambient temperatures seriously affect A. Water cooled units B. Air cooled units C. Compressors D. Dairy coolers - Solution A. Water cooled units 39. Water cooling towers require a periodic blow down to control A. Rainwater B. PH level above 20 C. Water overflow D. Scaling - Solution D. Scaling 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 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 - Solution C. Service port 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 - Solution A. Back seated 54. What type of oil is used with HFC refrigerant? A. Alkyl-benzene B. Mineral C. Flax seed D. Polyol Esther - Solution A. Alkyl-benzene 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 - Solution D. Controlling box temperature 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 - Solution 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 - Solution B. Evaporator pressure regulator (EPR) 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 - Solution C. Crank case pressure regulator (CPR) 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 - Solution C. Meter liquid refrigerant and oil at acceptable rate 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 - Solution B. To enable checking pressure drop across the dryer 61. A thermostatic expansion valve (TXV) that creates an unstable suction pressure is said to be A. Flashing B. Modulating C. Hunting D. Fractionating - Solution C. Hunting 62. Head pressure control valves permit hot gas to travel directly to the A. Condenser B. Evaporator C. Liquid receiver D. TXV - Solution B. Evaporator 63. Liquid slugging of the compressor can be caused by A. Low oil B. TXV hunting C. High superheat setting D. High ambient - Solution B. TXV hunting 64. A severe evaporator freeze up may cause A. High discharge pressure B. High suction pressure C. Liquid flood back D. Damage to TXV - Solution C. Liquid flood back 65. The oil separator is installed in the A. Suction line B. Discharge line C. Liquid line D. Hot gas bypass line - Solution B. Discharge line 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 - Solution A. Oil traps should be installed in all vapor carrying lines 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 - Solution D. Every 15 to 20 feet of vertical rise 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 - Solution C. Compression ratio A. Low refrigerant charge B. Defective valves in the compressor C. Refrigerant overcharge D. Product overload - Solution B. Defective valves in the compressor 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 - Solution B. Liquid refrigerant in the oil 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 - Solution 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 - Solution A. Debris from the burned compressor has clogged the filter dryer 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 - Solution B. The replacement filter dryer is larger than the original 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 - Solution B. The evaporator is starved due to a partial loss of refrigerant charge 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. Remo - Solution D. The accumulator contains liquid refrigerant and the surrounding temperature vaporizes the liquid, causing the low pressure switch to close prematurely 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 - Solution 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. 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 secure - Solution 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. 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