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All Textbook Solutions for Refrigeration and Air Conditioning Technology (MindTap Course List)

34RQ Explain what is meant by the range of a temperature control or pressure control.Name three types of automatic controls.Two categories ofelectric controls are_________and________.What circuit is energized with the thermostat Y circuit?The component in the system that is energized when the G terminal is energized is the ____.The ________terminal must be energized in the thermostat for the heat to start.The hot circuit in the thermostat is the _______terminal.Is the heat anticipator in series or parallel with the thermostat contacts?The cooling anticipator is wired A. in parallel with the cooling contact. B. next to the liquid line. C. in series with the cooling contact. D. inside the indoor unit.Which anticipator is adjustable, heat or cool?True or False: The indoor fan must always run during the cooling cycle.True or False: When the control transformer is not working, the indoor fan will not run in the FAN ON position.Which of the following should be turned off while working on the compressor circuit? A. The indoor unit fan B. The unit disconnect C. The thermostat D. The main power supply to the building The _______diagram is used to locate different components on the diagram in the unit.To trace the circuits in the unit, the _________diagramis used.15RQ 16RQ 17RQ True or False: Open switches will always read voltage.Explain why a service technician must always know where line 1 and line 2 are in relation to one another when voltage troubleshooting a schematic wiring diagram.True or False: Pneumatic controls are explosion-proof.Pneumatic controls are operated by A. water. B. electricity. C. electronics. D. air.One advantage of a modern control system is A. simplicity. B. faster response. C. ability to modulate. D. that they are less expensive.A control loop contains _______, _______, and _________.Pneumatic air must A. be clean and dry. B. have very high pressure. C. encompass a large volume. D. be hot.The air supplied to a diaphragm is 20 psig, and the diaphragm has a diameter of 6 in. How much pressure can this diaphragm apply to a plunger?When a large volume of air is needed at a diaphragm, the thermostat may feed branch line pressure to the_______.8RQ 9RQ An analog control signal A. has an infinite number of control steps. B. is very limited in the number of control steps. C. makes a hissing noise when the position is changed. D. is not used in this industry.Another term used to describe sensitivity in electronic controls is A. temperature. B. gain. C. rpm. D. pressure.12RQ 13RQ One of the major components of a residential electronic control circuit that measures temperature is a A. thermometer. B. thermistor. C. capacitor. D. filter.15RQ Describe a control device, and give three examples of these devices used in a DDC system in today's HVAC/R industry.Describe what a sensor does in a DDC system used in today's HVAC/R industry, and list five examples of sensors.What is the difference between an active and a passive sensor used in DDC control systems?A control system consists of what three basic components?List six advantages that DDC control systems have over traditional control systems.Describe the difference between the analog and digital signals in a DDC control system.Describe the difference between an open-loop and a closed-loop control configuration in a DDC system.The two popular operating voltages for residences are ______V and _____V.2RQ Is the resistance in the start winding greater or less than the resistance in the run winding?Which of the following devices may be wired into the starting circuit of a motor to improve the starting torque? A. Another winding B. A start capacitor C. A thermostat D. A winding thermostat 5RQ Define BEME.Why is the hermetic compressor motor manufactured from special materials?The two types of motors used for hermetic compressors are ______and_______.How does power pass through the compressor shell to the motor inside?The two types of relays used to start hermetic compressors are the _____relay and the _____.A PTC device is used A. to start a hermetic compressor. B. as a motor protector. C. to protect against low oil pressure. D. to protect against high oil temperature.True or False: Three-phase motors have low starting torque.13RQ Why is it desirable to have a two-speed compressor?True or False: All electric motors must be cooled or they will overheat.True or False: An SCR is an electronic switch.17RQ Capacitors are used after the converter to A. smooth out the DC current. B. suppress the noise. C. change the voltage frequency. D. reduce the voltage.The converter A. changes the frequency of the power. B. changes AC to DC. C. is a switch. D. is used only with DC motors.The inverter A. adjusts the frequency. B. adjusts the DC voltage. C. smooths out the AC power. D. makes a lot of noise.Briefly describe the operation of the three electronic sections of a variable frequency drive (VFD) using Figure 17.60 for assistance.1RQ Power supply data should include the followinginformation: A. ____________________ B. ____________________ C. ____________________ D. ____________________3RQ 4RQ 5RQ In the United States, the frequency in cycles per second (cps) at which an AC electric motor operates under normal conditions is A. 50. B. 60. C. 120. D. 208.7RQ 8RQ An open single-phase motor with a centrifugal starting switch may not be used in A. an air-conditioning condenser fan motor. B. an air-conditioning indoor air handler. C. an area where explosive gases exist. D. a ventilating fan motor.10RQ 11RQ 12RQ 13RQ 14RQ 15RQ What is a matched set of belts?Name the different types of belts.18RQ An instrument often used to check the alignment of two shafts is the A. micrometer. B. dial indicator. C. manometer. D. sling psychrometer.Why must resilient-mount motors have a ground strap?A belt-driven blower assembly is equipped with a motor that turns a 5-in. drive pulley at a speed of 3450 rpm. The blower is turning at a speed of 1725 rpm. Determine the size of the driven pulley.22RQ 23RQ 24RQ 1RQ 2RQ 3RQ 4RQ 5RQ 6RQ 7RQ What causes an overload protection device to function?9RQ 10RQ Why is it not a good idea to use circuit protection devices to protect large motors from overload conditions?Under what conditions are motors allowed to operate with slightly higher-than-design loads?Describe the difference between inherent and external overload protection.What is the purpose of overload protection at the motor?15RQ True or False: If a sleeve bearing fails in a small, fractional horsepower motor, the motor is generally replaced.An open winding in an electric motor means that A. the winding is making contact with the motor frame. B. one winding is making contact with another winding. C. a wire in one winding is broken. D. the centrifugal switch to the start winding is open.There is a short circuit in an electric motor winding when A. there is an adverse weather condition. B. a winding conductor is worn bare and touches anotherpart of the conductor that is also bare. C. there is a defect in the centrifugal start switch. D. the motor will not start.An open winding or a shorted winding can be determined with which of the following instruments? A. Voltmeter B. Ammeter C. Ohmmeter A decrease in resistance will cause the amperage to A. decrease. B. increase. C. decrease or increase. D. none of the above.6RQ 7RQ To determined the capacitance of a capacitor, a (n)___________should be used.State the physical differences between a run and a start capacitor.10RQ Describe what may happen to an electric motor if the drive belt is too tight.How are the electrical components checked on a hermetic compressor?13RQ The amperage can be checked with a(n)_______anneter.Electric motor roller and ball bearing failure often can be determined by the _____.What is the function of the evaporator in the refrigeration system?Refrigerant in the evaporator A. changes from vapor to liquid. B. changes from liquid to vapor. C. stays in the vapor state. D. stays in the liquid state.The sensible heat that is added to a saturated vapor after all of the liquid has boiled away is referred to as _____.What determines the pressure on the low-pressure side of the system?A refrigerant system's evaporator typically runs about ______degrees of superheat.What does a high evaporator superheat indicate?A low evaporator superheat indicates A. undercharge. B. system restriction. C. overcharge. D. dirt buildup.Why is a multicircuit evaporator used?Flooded evaporators use a(n) ______type of expansion device.An evaporator that is not flooded is thought of as what type of evaporator?When an evaporator experiences a heat-load increase, the suction pressure A. remains constant. B. decreases. C. varies up and down. D. increases.What is commonly used to defrost the ice from a low-temperature evaporator?A medium-temperature refrigeration box operates within what temperature range? A. 28F to 40F B. 40F to 60F C. 0F to -20F D. 0F to 50F List seven advantages that an aluminum parallel-flow, plate/fin evaporator has over a standard round, copper-tube plate/fin evaporator.Why do some condensers have to be cleaned with brushes and others with chemicals?The three materials of which condensers are normally made are _____, and ____.Who should be consulted when condenser cleaning is needed?When is the most heat removed from the refrigerant in the condensing process?After heat is absorbed into a condenser medium in a water-cooled condenser, the heat can be deposited in one of two places. What are they?A water-cooling tower capacity is governed by what aspect of the ambient air? A. Dry-bulb temperature B. Wet-bulb temperature C. Enthalpy of the air D. Altitude When a standard-efficiency air-cooled condenser is used, the condensing refrigerant will normally be higher in temperature than the entering air temperature.Four methods for controlling head pressure in an air-cooled condenser are ______, ______, _______, and The prevailing winds can affect which of the air-cooled condensers?True or False: Air-cooled condensers are much more efficient than water-cooled condensers.The type of condenser that has the lowest operating head pressure is the _______cooled condenser.Compare the standard conditions of high-efficiency and standard air-cooled condensers.Name two ways in which the heat from an air-cooled condenser can be used for reclaiming heat.Briefly describe what is meant by floating head pressure, and tell why it is used in refrigeration and air-conditioning systems.Explain how to flush impurities from a water-regulating valve that is on a water-cooled condenser.Explain the basic operation of a combination ORI and ORD low-ambient head pressure control valve.Name two problems a refrigeration system may have if the condensing unit is exposed to a low-ambient condition when not equipped with a low-ambient head pressure control valve.Briefly explain what is meant by condenser splitting, and list its main advantage.Describe the operation of a compressor.Name five types of compressors.True or FAlse: A compressor can compress a liquid.What would be considered a higher-than-normal temperature for a discharge gasline on a reciprocating compressor? A. 190F B. 215F C. 250F D. All of the above Which compressor type uses pistons to compress the gas? A. Scroll B. Reciprocating C. Rotary D. Screw Which compressor type uses tapered, machined gear components to trap the gas for compression? A. Scroll B. Reciprocating C. Rotary D. Screw Which style of compressor uses belts to turn the compressor? A. Open drive B. Closed drive C. Chassis drive D. Hermetic drive What would be done to increase the compressor speed on a belt-driven compressor? A. Decrease drive pulley size B. Increase drive pulley size C. Increase driven pulley size D. Both A and C Describe the reciprocating compressor piston, rod, crank-shaft, valves, valve plate, head, shaft seal, internal motor overload device, pilot-duty motor overload device, and coupling.Name two things in the design of a reciprocating compressor that control the efficiency of the compressor. A. ___________ B. ___________.At what speeds in rpm does a hermetic compressor normally turn? A. 1750 B. 3450 C. 4500 D. Both A and B What effect does a slight amount of liquid refrigerant have on a compressor over a long period of time?What lubricates the refrigeration compressor? A. Refrigerant B. Moisture C. Desiccants D. Oil What can the service technician do to keep the refrigeration system operating at peak efficiency?State the main advantage that a discus compressor's valve plate design has over a conventional piston-type compressor.Briefly describe how the scroll compressor compresses refrigerant gas.List four main advantages a scroll compressor has over a conventional piston-type compressor.What are two main reasons why a compressor should have modulating capacity control?Briefly describe how the digital capacity control for a scroll compressor works.List the three main advantages of having digital capacity control on a scroll compressor.21RQ Which is not a pressure or force acting on a TXV diaphragm? A. Head pressure B. Evaporator pressure C. Spring pressure D. Bulb pressure The needle and seat of a TXV are normally made of ______.The TXV tries to maintain a constant _____in theevaporator.The four types of charges that the TXV uses to control refrigerant flow are ____, ____, ____, and ______.5RQ When do some TXVs require an external an external equalizer?Draw a diagram showing how an external equalizer line is connected into a system.The TXV responds to an increased heat load by A. decreasing refrigerant flow. B. keeping refrigerant flow constant. C. increasing refrigerant flow. D. not reacting to changing heat loads.The three factors that determine the capacity of a T XV are ______, ______, and _____.Explain why the entering liquid pressure has no effect on the opening force of a balanced-port TXV.11RQ Explain the following terms as they apply to electronic expansion valves: step motor offset error algorithm microprocessor feed back loop 13RQ How does the automatic expansion valve respond to a load increase?What determines the amount of refrigerant that flows through a capillary tube metering device?Explain what is meant by a maximum operating pressure (MOP) TXV.Which is not a basic component of the compression refrigeration cycle? A. Compressor B. Condenser C. Evaporator D. Suction filter Describe modulating fluid flow.The purpose of the crankcase pressure-regulating valve is to A. maintain constant pressure in the crankcase. B. maintain constant pressure in the evaporator. C. prevent a compressor from going into a vacuum. D. prevent a compressor overload condition.Describe the function of an electric evaporator pressure-regulating (EEPR) valve.5RQ Briefly describe the function of a non-short-cycling, or "one-time," automatic pumpdown system.Two types of relief valves are_______and ______.Why is low-ambient control necessary?Which is not a method of low-ambient control on air-cooled equipment? A. Modulating TXV B. Fan-cycling controls C. Flooding a condenser D. Fan speed control Describe the devices in questions 10-13.Low-pressure switch High-pressure switch Low-ambient(switch)Oil safety switch What is the function of the current sensing relay in an oil safety control scheme?Why is there a time delay in an oil safety control?What is off-cycle defrost?Two types of off-cycle defrost are______and ______.Two methods for accomplishing defrost on low-temperature refrigeration systems are ____and___. Describe how the components in questions 19-23 enhance the refrigeration cycle.Filter drier Heat exchanger Suction accumulator Receiver 23RQ 24RQ What will happen if the float in an oil separator collapses?The function of the evaporator pressure regulator is to A. maintain a constant evaporator pressure. B. prevent a minimum pressure in the evaporator. C. maintain a constant evaporator temperature. D. prevent a maximum pressure in the evaporator.What is the function of the oil return hole or orifice in a suction accumulator?What is the function of the pressure equalization orifice at the outlet of an accumulator?The two broad categories of display cases are _______and _______.How are conditions maintained in open display cases when there are high shelves?What are mullion heaters?The three temperature ranges for refrigeration systems are_____, ______, and____.The two methods for rejecting heat from refrigerated cases are _______and ______.When the compressors are located in the equipment room, the piping is routed A. in floor chases or in plastic pipes under the floor. B. in suspended ceilings. C. between the walls. D. in back of the walls.When one large compressor is used, what desirable feature should it have? A. Discharge muffler B. Suction muffler C. Cylinder unloaders or variable-speed drive D. Hot gas bypass Define a parallel compressor system and list five advantages of these systems.Three disadvantages of parallel compressor systems are _____, _____, and ____.What is the difference between an even and an uneven parallel compressor system?Exactly matching the refrigeration load with the capacity of refrigeration compressors is referred to as A. capacity control. B. load shedding. C. load paralleling. D. load matching.What is the function of the pressure transducer in parallel compressor systems?What is the function of the microprocessor-based controller in parallel systems?Explain how the oil separator, oil reservoir, pressure differential valve, and oil-level regulators work together tomaintain the correct oil level in parallel compressors.Large or small compressors on parallel compressor racks, which are usually dedicated to the coldest cases, are called A. satellite compressors. B. remote compressors. C. booster compressors. D. both A and C.A(n)_______varies the frequency of an electronically altered sine wave, which affects the speed of alternating current motors.17RQ 18RQ Three advantages of unitary, stand-alone refrigeration modules in supermarket refrigeration are ______and _______.How is defrost accomplished when the equipment room is in the back and the medium-temperature fixtures are in the front?True or False: The two types of defrosts used with low-temperature fixtures are hot gas and electric defrost.What special precautions should be taken with drainlines in walk-in coolers? A. Freeze protection B. Trapping to prevent air from being pulled in C. Downward sloping D. All of the above 23RQ What special valve is used in a refrigerated air drier? A. Four-way valve B. Defrost valve C. Three-way valve D. Hot gas bypass valve Briefly explain what is meant by a surge-type receiver.Briefly explain what is meant by a subcritical refrigeration cycle, and list its four processes.Briefly explain what is meant by a transcritical refrigeration cycle, and list its four processes.28RQ 29RQ 30RQ 31RQ 32RQ 33RQ Which type of ice maker has a continuous harvest cycle?Which type of ice is made using a gear motor and auger? A. Cube ice B. Cylinder ice C. Flake ice D. Block ice What would be the symptoms of a defective float on an ice maker?What are the two functions of the dual float switch in an ice flake machine?Which part of an ice flake machine is most prone to failure? A. The gear motor B. The float mechanism C. The ice chute D. The compressor List two causes that may lead to auger wobble.What is the function of a flush cycle for an ice flake machine?Name and explain three types of ice bin controls iniceflake machines.Ice production in an ice flake machine depends mainly on two factors. Name and briefly explain these two factors.Explain the function of weep holes on the evaporator of a cell-type ice maker.True or False: Stainless steel is often used for evaporators because it is durable, very sanitary. and resists corrosion.Explain what is meant by ice bridging in a cell-type ice maker.Explain the function of the centrifugal pump in ince makers.What is the function of the ice thickness probe in an ice maker?15RQ What is the most common type of defrost during an ice maker harvest cycle? A. Electric B. Natural C. Hot gas D. Air Explain how liquid floodback to the compressor may occur during an ice maker hot gas defrost period.18RQ 19RQ 20RQ 21RQ One of the quickest and most thorough ways of obtaining technical service information for an ice machine is through the A. manufacturer. B. wholesale store. C. Internet. D. fax machine.23RQ 24RQ True or False: Entering-air temperature and water temperature are the main factors determining the amount of ice produced in an air-cooled ice machine.A measurement that represents the thermal cooling capacity of ice and also represents the amount of calcium and magnesium in water is A. hardness. B. turbidity. C. alkalinity. D. scale.A buildup of minerals that forms a flaky coating on the surface of the evaporator and water system is called A. sediment. B. scale. C. hardness. D. turbidity A method for killing bacteria, viruses, and protozoa in ice machines is A. sanitizing. B. cleaning. C. rinsing. D. brushing.29RQ 30RQ True or False: A common type of water filtration and treatment for ice machines is a triple-action filter system.32RQ 33RQ List the evaporating temperatures for liquid nitrogen and CO2: _____and____.2RQ 3RQ 4RQ 5RQ 6RQ 7RQ Which are power supplies used for truck refrigeration? A. Gas-engine driven compression B. Electric compressor operated with a motor generator C. Diesel compressor D. All of the above What type of reserve capacity does truck refrigeration have?Why is truck refrigeration designed to provide low- and medium-temperature refrigeration?How is the air distributed over the cargo in truck refrigeration?Name two types of engines used for truck refrigeration systems.13RQ Truck trailers with their own refrigeration systems, which are transported on railway cars, are called A. self-contained refrigeration systems. B. piggyback refrigeration systems. C. double-layer refrigeration systems. D. dependent refrigeration systems.Why is two-stage compression popular for extra-low-temperature refrigeration systems?An R-404A system is operating with a -50F evaporator and the condenser is operating at 115F. What is the compression ratio of this system? A. 16.9 to 1 B. 17.8 to 1 C. 19.1 to 1 D. 21.33 to 1 Describe cascade refrigeration and tell why more than one refrigerant is used.Why is a circulating brine system more attractive for ship refrigeration than individual evaporators?Two methods used to power refrigeration compressors on a ship are _____and ____.

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