Download Refrigeration System Components and Troubleshooting and more Exams Nursing in PDF only on Docsity!
Commercial Refrigeration Certification
actual solution
"Pump down" means to capture system refrigerant in the: A. recovery cylinder. B. compressor. C. condenser and/or liquid receiver. D. suction accumulator. - correct answer ✅✅ C. condenser and/or liquid receiver. A _____ is usually required for ultra-low temperature applications. A. cooler B. comfort cooling system C. freezer D. cascade system - correct answer ✅✅ D. cascade system A _____ type metering device is best suited in applications where freeze protection is required. A. thermostatic expansion valve (TEV) B. automatic expansion valve (AEV)
C. float D. capillary tube - correct answer ✅✅ B. automatic expansion valve (AEV) A customer calls and 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 bell of Ice. The technician decides to advance the electromechanical defrost timer to the next defrost period and observe the defrost function. In doing so, the evaporator defrosts to the level of the ice build-up, 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 sec - correct answer ✅✅ 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 force to damage the flare, creating a slow refrigerant leak. 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 the unit's erratic behavior may have contributed to the higher bill. The technician arrives and
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 attempts to reset the switch. The switch will not reset and the motor frame is very hot. Using ice from another machine in a heavy plastic bag, the motor is coo - correct answer ✅✅ C. the lack of water flow reduced evaporator load, which resulted in the auger freezing up and the drive motor tripping the overload. The low pressure and current are the result of low load on the evaporator. Water flow must be restored and the machine should operate properly. 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 confirms the owner's complaint of thin ice and low production. Further inspection reveals that the ice machine Is equipped with a harvest solenoid and a thermostatic expansion valve. The water pump is operating and 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 check 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 sub cooling ind - correct answer ✅✅ D. the harvest solenoid ls leaking. keeping the suction pressure above normal, and must be replaced.
A customer reports that their low temperature reach-in freezer had a burned compressor replaced last week by another service company, and now is not cooling properly. When you arrive and examine the system, you find that the evaporator seems to be starving for refrigerant. On inspecting the condensing unit, you notice that the liquid line is sweating where it leaves the filter drier. This is most likely the result of: A. debris from the burned compressor has clogged the filter drier. B. air in the system. C. low refrigerant charge. D. refrigerant overcharge. - correct answer ✅✅ A. debris from the burned compressor has clogged the filter drier. A defrost cycle can be initiated by a: A. timer. B. defrost thermostat. C. pressure control. D. control thermostat - correct answer ✅✅ A. timer. A defrost cycle can be terminated by the: A. low ambient control. B. condensing temperature.
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 spaced closer together. C. must be frosted periodically. D. must be defrosted periodically. - correct answer ✅✅ D. must be defrosted periodically. A Michigan servicemen is called 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 OK, 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 drier. - correct answer ✅✅ B. Faulty condenser ambient controls. A multiple compressor system uses individual pressure controls for each: A. evaporator.
B. condenser. C. compressor. D. exhaust. - correct answer ✅✅ C. compressor. A properly functioning condenser will first: A. condense then de-superheat. B. subcool then de-superheat. C. subcool then superheat. D. de-superheat then subcool. - correct answer ✅✅ D. de- superheat then subcool. A refrigeration system used to cool another refrigeration system is called a: A. piggyback system B. cascade system. C. twin system. D. parallel system. - correct answer ✅✅ B. cascade system. 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 over the top one third of the coil. Measuring the evaporator superheat,
C. allowing the separator to return oil to the crankcase during the off cycle only. D. allowing the system to equalize during the off cycle. - correct answer ✅✅ D. allowing the system to equalize during the off cycle. 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. - correct answer ✅✅ D. Defective defrost timer. 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. - correct answer ✅✅ A. low refrigerant charge.
A technician has performed a leak repair on a vending machine that uses a self-contained refrigeration system that employs a capillary tube metering device. After repairing the leak, the filter drier was replaced and 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 manufactures specifications. Which of the following could cause these low readings? A. There is too much oil is the system. B. The replacement filter drier is larger than the original. C. Ambient temperature is 95°F. D. Ambient temperature is 72°F. - correct answer ✅✅ B. The replacement filter drier is larger than the original. 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. - correct answer ✅✅ D. a blocked distributor. A TEV with an external equalizer is used on:
An automatic pump down system requires a: A. liquid line solenoid. B. suction accumulator. C. thermostatic cut-out D. fan cycle switch. - correct answer ✅✅ A. liquid line solenoid. An evaporator used to chill liquids in operating with a normal superheat setting, but the system is not cooling the product properly. Which of the following is the most likely cause? A. overcharge of refrigerant B. undercharge of refrigerant C. the circulator D. the TEV - correct answer ✅✅ C. the circulator An expansion device that is stuck open will cause: A. low suction pressure B. a starved evaporator. C. excessive superheat D. a flooded evaporator - correct answer ✅✅ D. a flooded evaporator An oil pressure differential switch utilizes which of the following pressures in opening the contacts to 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. - correct answer ✅✅ D. Compressor crankcase pressure and oil pump discharge pressure. An oil separator must be kept warm in order to: A. prevent sluggish return of the oil to the crankcase. B. prevent refrigerant from condensing in the 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. - correct answer ✅✅ A. prevent sluggish return of the oil to the crankcase. An open drive compressor is most likely to develop a refrigerant leak at the: A. valve plate. B. suction service valve. C. discharge service valve. D. shaft seal. - correct answer ✅✅ D. shaft seal.
A. low oil level condition. B. refrigerant In the oil. C. too much oil in the crankcase. D. moisture in the oil. - correct answer ✅✅ B. refrigerant In the oil. Capacity control of a large compressor can be performed with: A. solenoid valve. B. hand valves. C. unloaders. D. dampers. - correct answer ✅✅ C. unloaders. Cooling towers that pass air over water to remove system heat are limited in capacity by: A. outside air wet bulb temperature. B. outside air dry bulb temperature C. inside air wet bulb temperature. D. inside air dry bulb temperature. - correct answer ✅✅ A. outside air wet bulb temperature. Defrostlng a low temperature evaporator can be accomplished by: A. stopping the evaporator fan motor. B. reversing the compressor rotation.
C. using electric heaters. D. installing a modulating valve. - correct answer ✅✅ C. using electric heaters. Dry type evaporators operate most efficiently with a 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 - correct answer ✅✅ A. 8° F to 12°F Ester based oils are: A. aromatic blends. B. vegetable in origin. C. a synthetic oil. D. not a popular choice for retrofit. - correct answer ✅✅ C. a synthetic oil. Excessive frost on the evaporator causes: A. increased efficiency. B. reduced heat transfer. C. high humidity. D. increased superheat. - correct answer ✅✅ B. reduced heat transfer.
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 - correct answer ✅✅ C. 25 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. - correct answer ✅✅ D. every 15 to 20 feet of vertical rise. 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 degrees B. 20 degrees C. 30 degrees D. 40 degrees - correct answer ✅✅ B. 20 degrees
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. - correct answer ✅✅ A. oil traps should be installed in all vapor carrying lines. 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 does not accumulate. C. sub-cool the compressor. D. ensure proper oil return. - correct answer ✅✅ A. operate at high efficiency. Liquid slugging of the compressor can be caused by: A. low oil. B. TEV hunting. C. high superheat setting. D. high ambient. - correct answer ✅✅ B. TEV hunting. Low ambient temperatures seriously affect:
