Commercial Refrigeration Certification
The refrigerant condensing temperature in a water cooled condenser is normally about ____ higher than the leaving water. A. 100°F B. 10°F C. 30°F D. 75°F
B. 10°F
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
B. 20 degrees
The refrigerant in an air cooled condenser will normally condense 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
A defrost cycle is required whenever the evaporator must operate below: A. 0°F B. 32°F C. 10°F D. 20°F
B. 32°F
What time interval is required between each superheat adjustment? A. Not less than 1 hour B. About 10-15 minutes C. At least 1/2 hour. D. No time delay.
B. About 10-15 minutes
What is the normal operating position for two-way service valves? A. Front seated B. Back seated C. Cracked D. Closed
B. Back seated
What valve is used to connect multiple evaporators of different temperatures to a single compressor? A. Crankcase pressure regulator (CPR). B. Evaporator pressure regulator (EPR). C. Oil pressure regulator. D. Head pressure regulator.
B. Evaporator pressure regulator (EPR).
What valve is used to prevent evaporator pressure from falling below a set limit? A. Crankcase pressure regulator (CPR). B. Evaporator pressure regulator (EPR). C. Oil pressure regulator. D. Head pressure regulator.
B. Evaporator pressure regulator (EPR).
Liquid slugging of the compressor can be caused by: A. low oil. B. TEV hunting. C. high superheat setting. D. high ambient.
B. TEV hunting.
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.
Vibration eliminators should be installed _____ to the compressor crankshaft centerline. A. Perpendicular B. parallel C. vertical D. at a 90° angle
B. parallel
The automatic expansion valve (AEV) maintains a constant _____ in the evaporator. A. temperature B. pressure C. liquid level D. superheat
B. pressure
A multiple compressor system uses individual pressure controls for each: A. evaporator. B. condenser. C. compressor. D. exhaust.
C. compressor.
The suction accumulator prevents liquid refrigerant from entering the: A. evaporator. B. condenser. C. compressor. D. heat exchanger.
C. compressor.
"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.
A thermostatic expansion valve (TEV) that creates an unstable suction pressure is said to be: A. flashing. B. modulating. C. hunting. D. fractionating.
C. hunting.
A severe freeze-up may cause: A. high discharge pressure. B. high suction pressure. C. liquid flood back. D. damage to TEV.
C. liquid flood back.
Head pressure control valves permit hot gas to travel directly to: A. condenser. B. evaporator. C. liquid receiver. D. TEV.
C. liquid receiver.
Capacity control of a large compressor can be performed with: A. solenoid valve. B. hand valves. C. unloaders. D. dampers.
C. unloaders.
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.
D. must be defrosted periodically.
Water cooling towers require: A. distilled water. B. a chlorobutyl liner. C. weekly de-scaling. D. periodic de-scaling.
D. periodic de-scaling.
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. liquid flooding back to the compressor. D. refrigerant migration to the compressor crankcase during the on-cycle.
D. refrigerant migration to the compressor crankcase during the on-cycle.
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.
D. shaft seal.
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
What is the viscosity of most oils used in refrigeration systems? A. 100 B. 200 C. 300 D. 400
A. 100
High temperature refrigeration applications normally provide box temperatures of: A. 47°F to 60°F B. 35°F to 45°F C. 40°F to 55°F D. 45°F to 55°F
A. 47°F to 60°F
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
A. 8° F to 12°F
Which refrigerant line is most sensitive to Improper sizing? A. Liquid line. B. Suction line. C. Discharge line. D. Condensate line.
A. Liquid line.
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.
Short cycling during pump down can be caused by: A. a leaking compressor suction valve. B. a leaking TEV seat. C. air in the system. D. a leaking cylinder unloading device.
A. a leaking compressor suction valve.
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.
When work on a refrigeration system is complete, the service valves should be in this position: A. back seated. B. front seated. C. cracked. D. midpoint.
A. back seated.
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. (Suction Line)
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.
A. debris from the burned compressor has clogged the filter drier.
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.
A TEV with an external equalizer is used on: A. evaporators with a high pressure drop. B. evaporators with a low pressure drop. C. high temperature applications only. D. all evaporators.
A. evaporators with a high pressure drop.
An automatic pump down system requires a: A. liquid line solenoid. B. suction accumulator. C. thermostatic cut-out D. fan cycle switch.
A. liquid line solenoid.
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.
A. low refrigerant charge.
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.
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.
A. operate at high efficiency.
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.
A. outside air wet bulb temperature.
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.
A. prevent sluggish return of the oil to the crankcase.
A defrost cycle can be initiated by a: A. timer. B. defrost thermostat. C. pressure control. D. control thermostat
A. timer.
Tube within a tube, shell and coil, and shell and tube are all types of: A. water cooled condensers. B. air cooled condensers. C. receivers. D. accumulators.
A. water cooled condensers.
Low ambient temperatures seriously affect: A. water cooled units. B. air cooled units. C. ice cream units. D. dairy coolers.
A. water cooled units.
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.
B. Faulty condenser ambient controls.
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.
B. The replacement filter drier is larger than the original.
When measuring oil pressure on a 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 pressurized system.
B. actual oil pressure must be calculated by subtracting suction pressure from the oil pressure gauge reading.
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 in gallons per minute. B. adjusting the valve 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 valve to the design condensing temperature.
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
B. automatic expansion valve (AEV)
A refrigeration system used to cool another refrigeration system is called a: A. piggyback system B. cascade system. C. twin system. D. parallel system.
B. cascade system.
One of the main reasons that reciprocating compressors are not 100% efficient is: A. CFC refrigerants. B. clearance volume. C. evaporator design D. condenser design.
B. clearance volume.
The two manually adjusted 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.
B. differential and cut-out.
The oil separator is installed in the: A. suction line. B. discharge line. C. liquid line. D. hot gas bypass line.
B. discharge line.
The "Fan Cycle Control" is used in low ambient conditions to control: A. suction pressure. B. head pressure. C. evaporator fans. D. compressor fan.
B. head pressure.
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.
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 secured in their normal positions. Manifold gauges are connected to the service ports 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 and 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 force to damage the flare, creating a slow refrigerant leak. C. the system Is leak free, but the ice that formed on the evaporator and expansion valve caused excessive sub-cooling of the liquid refrigerant preventing the liquid from changing state as it would have under normal pressure drop conditions. D. the system Is leak free, but the defrost timer defrost period 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 force to damage the flare, creating a slow refrigerant leak.
Excessive frost on the evaporator causes: A. increased efficiency. B. reduced heat transfer. C. high humidity. D. increased superheat.
B. reduced heat transfer.
Bubbles or foaming In the compressor's oll sight glass are an indication of: A. low oil level condition. B. refrigerant In the oil. C. too much oil in the crankcase. D. moisture in the oil.
B. refrigerant In the oil.
Name an electrically operated shut-off valve: A. automatic expansion valve. B. solenoid valve. C. check valve. D. isolation valve.
B. solenoid valve.
With blended refrigerants, the difference between the boiling point (bubble point) and condensing point (dew point) is called: A. temperature slip. B. temperature glide. C. temperature rate. D. electraglide.
B. temperature glide.
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, the technician finds that it is 22 degrees. A check of system pressures indicates lower than normal suction and discharge pressures. A check of condenser sub-cooling shows 2 degrees. 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 TEV sensing bulb has probably lost its charge and must be replaced.
B. the evaporator is starved due to a partial loss of refrigerant charge.
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
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. Crankcase pressure regulator (CPR). D. Oil pressure regulator.
C. Crankcase pressure regulator (CPR).
When a service valve is back seated, which port is closed? A. Outlet port. B. Inlet port. C. Service port. D. Pilot port.
C. Service port.
Ester based oils are: A. aromatic blends. B. vegetable in origin. C. a synthetic oil. D. not a popular choice for retrofit.
C. a synthetic oil.
Multiple compressors provide: A. positive on return. B. lower humidity in high humidity locales. C. capacity control D. zone control.
C. capacity control
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.
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.
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
C. the circulator
A customer complains that their counter top ice machine is making a loud noise and not producing any ice. Upon arrival, the technician removes the front panel and determines that the noise is coming from the ice machine auger. Before the technician can unplug the power supply, the auger drive motor overload opens and the drive motor stops. The machine's compressor continues to operate. The technician unplugs the ice machine and attaches 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 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 cooled 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 and falls below normal about the same time as the noise begins. The high side pressure is slightly lower than 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 find 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 opened the motor overload. B. the system has an undercharge 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 low pressure and current are the result of low load on the evaporator. Water flow must be restored and the machine should operate properly. D. the gear box 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 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 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 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 shuts the unit down, locking 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 build-up from the outlet of the liquid line solenoid to the expansion valve. Manifold gauges are attached to the service ports. Removing the lock and tag from 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 hears the audible click of the liquid line solenoid as the thermostat is satisfied and the condensing unit continues to run until the low pressure switch cycles the unit off. Again the unit repeats the short cycling condition. The technician determines that: A. the low pressure switch is misadjusted and 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.
C. the liquid line solenoid is leaking during the off cycle, causing the low pressure switch to cycle the condensing unit.
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.
C. using electric heaters.
The term "cryogenics" refers to refrigeration systems operating in 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
At what evaporator temperature does an Ice maker begin to make ice? A. 32°F B. 0°C C. 0°F D. 20°F
D. 20°F
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
On a rack of multiple compressors, each compressor is controlled by: A. suction pressure transducer. B. thermostat. C. interstage pressure. D. Crankcase Pressure Regulating valve (CPR).
D. CPR valve.
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.
D. Compressor crankcase pressure and oil pump discharge pressure.
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.
D. Defective defrost timer.
What type of oil is used with HFC refrigerant? A. Alkylbenzene B. Mineral C. Ab / min D. Polyol ester
D. Polyol ester
What Is the most likely cause of the following symptoms? The compressor shuts off on the oil pressure switch. The oil sight glass is 1/2 full. Suction pressure is 3 psig (R-502). Oil pressure is 70 psig. A. Defective oil pump. B. Insufficient oil. C. Defective oil pressure switch. D. Suction pressure too low.
D. Suction pressure too low.
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.
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
A solenoid valve (N.C.), energized during the run cycle, is often used in the oil return line between the separator and the compressor crankcase for the purpose of: A. Isolating the separator from the low side during the off cycle In the event of a leaking ball and float assembly. B. preventing migration of refrigerant to the separator during the off cycle. 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.
D. allowing the system to equalize during the off cycle.
A _____ is usually required for ultra-low temperature applications. A. cooler B. comfort cooling system C. freezer D. cascade system
D. cascade system
A low pressure switch can be used for: A. overcharge protection. B. high side cut-out. C. control refrigerant flow rate. D. control of space temperature.
D. control of space temperature.
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.
D. de-superheat then subcool.
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 foaming in the crankcase.
D. dilution of the oil and foaming in the crankcase.
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.
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 alkylbenzene oil. C. you must add a napthenlc oil. D. extensive oil flushing is required.
D. extensive oil flushing is required.
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
Some special applications use a flooded evaporator (operated full of refrigerant). In order to maintain the proper level of liquid refrigerant, a ____ type metering device is used. A. TEV B. capillary tube C. AEV D. float
D. float
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.
Automatic pump down systems are used to prevent: A. power surges on demand utility systems. B. surges of liquid refrigerant (slugging) during shut-down. C. oil foaming at shut-down. D. migration of refrigerant to the crankcase during off cycles.
D. migration of refrigerant to the crankcase during off cycles.
A defrost cycle can be terminated by the: A. low ambient control. B. condensing temperature. C. head pressure. D. suction pressure.
D. suction pressure.
The thermostatic expansion valve (TEV) maintains a constant _____ in the evaporator. A. temperature B. pressure C. liquid level D. superheat
D. superheat
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 indicates 15°F. The technician determines that: A. the system is undercharged and must be topped off to correct the problem. B. the thermostatic expansion valve is improperly 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 drier changed, the system evacuated. and recharged by weight. D. the harvest solenoid ls leaking. keeping the suction pressure above normal, and must be replaced.
D. the harvest solenoid ls leaking. keeping the suction pressure above normal, and must be replaced.
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.
Superheat measurements are best taken: A. during a hot pull down. B. at 8°F to 12°F. C. during defrost. D. with the system operating at design conditions.
D. with the system operating at design conditions.
