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All Textbook Solutions for Refrigeration and Air Conditioning Technology (MindTap Course List)
Capacitors should be shorted with a(n) ______before checking with an ohmmeter.The high- and low-side pressures on an operating air-conditioning system can be converted to the ______and ______temperatures by using a temperature/pressure relationship chart.Why do most air-conditioning systems not need a defrost system?A typical standard-efficiency evaporator under standard conditions will operate at a temperature of A. 30F. B. 40F. C. 50F. D. 60F.The typical temperature difference between the entering air and the boiling refrigerant on a standard air-conditioning evaporator is ______F.When the ambient outside air temperature isand the unit is a high-efficiency unit, the lowest condensing refrigerant temperature when the unit is operating properly is A. 110F. B. 115F. C. 120F. D. 125F.When the outside ambient air temperature is 90F, the temperature of the condensing refrigerant in a standard- efficiency unit should be approximately A. 120F. B. 130F. C. 140F. D. 150F.If a condensing pressure is 260 psig for R-22, thecondensing temperature will be A. 110F. B. 120F. C. 130F. D. 140F.How is high efficiency accomplished in an air-conditioning condensing unit?True or False: When troubleshooting a small system, the first step is to attach the high- and low-pressure gauges.The suction gas may have a high superheat if the unit hasa(n)________charge.If the suction pressure is low and the suction line is warm, the system has a _____evaporator. A. full B. starvedWhat electrical test instrument is used to measure continuity in a compressor winding?What electrical test instrument is used to measure the current draw of a compressor?Most condensers will subcool the refrigerant to between ____F below the condensing temperature of the refrigerant. A. 0 and 5 B. 5 and 10 C. 10 and 20 D. 20 and 30What are two types of fixed-bore metering devices?It no crankcase heat is at the compressor, what may happen to the refrigerant charge?What is the purpose of the internal overload protector in the compressor motor?If a condenser circuit breaker is tripped, you should A. reset it. B. check the suction pressure. C. check the high-side pressure. D. perform a resistance check of the compressor section.An oversized air-conditioning system will A. cost more to install and operate. B. be more efficient than an undersized air-conditioning system. C. be better able to maintain the desired humidity in theconditioned space. D. require a smaller air distribution system than an undersized air-conditioning system.Methods used to calculate the heat gain and heat loss of a structure should A. provide the same results for all houses with the samesize footprint. B. provide only a very rough estimate of the needs of thestructure. C. be nationally recognized and accepted. D. All of the above are correct.An exterior wall A. separates a conditioned interior space from an unconditioned interior space. B. separates an interior conditioned space from theoutside. C. separates one interior conditioned space from another conditioned interior space. D. separates an interior unconditioned space from the outside.A partition wall A. separates a conditioned interior space from an unconditioned interior space. B. separates an interior conditioned space from the outside. C. separates one interior conditioned space from another conditioned interior space. D. separates an interior unconditioned space from the outside.As the temperature differential across a panel increases, A. the rate of heat transfer through the panel will increase. B. the rate of heat transfer through the panel will decrease. C. the rate of heat transfer through the panel will remain unchanged since the temperature difference does not affect the rate of heat transfer.The typical indoor design temperature used for heat gaincalculations is A. 65F. B.70 F. C.75 F. D. 80F.The typical indoor design temperature used for heat loss calculations is A. 65F. B. 70F. C. 75F. D. 80F.If a heating system was being designed for use in Modesto, California, what temperature difference would be used for calculations? A. 30F B. 40F C. 50F D. 60FIf an air-conditioning system was being designed for usein Nogales, Arizona, what temperature difference would be used for calculations? A. 21F B. 68F C. 75F D. 96FIf the R-value of a construction material is 2.0, what isits U-value? A. 0.25 B. 0 50 C. 1.0 D. 2.0If a wall is made up of four different materials, all layered one on top of the other, how will the total R-value of the wall be determined? A. By the one material with the highest R-value B. By the one material with the lowest R-value C. By averaging the R-values of the materials D. By adding the R-values of the materials together12RQAll of the following are taken into account on a heat gain calculation except A. exterior walls. B. partition walls. C. basement floors. D. top-floor ceilings.How much heat is lost through a 3' 5' single-pane window with a storm that is exposed to a 60F temperature differential? A. 450 Btu/h B. 900 C. 1350 Btu/h D. 1800 Btu/hWhich of the following is(are) true regarding a 10' × 30' wall that has a 21-ft2 door and a 20-ft2 window cut into it? A. The gross wall area is 300 ft2. B. The net wall area is 259 ft2. C. Both A and B are correct. D. Neither A nor B is correct.Which of the following is(are) true regarding the solar gain on windows? A. The solar gain due to north-facing windows is greater than the solar gain due to south-facing windows. B. The solar gain due to east-facing windows is greater than the solar gain due to west-facing windows. C. The solar gain due to west-facing windows is greaterthan the solar gain due to east-facing windows. D. The solar gain due to south-facing windows is greaterthan the solar gain due to north-facing windows.How does a heart pump resemble a refrigeration system?Name the three common sources of heat for heat pumps.What large line connects the indoor unit to the outdoorunit? A. A discharge line B. A liquid line C. An equalizer line D. A gas lineWhy is the indoor unit not called an evaporator?When is the outdoor unit called an evaporator? A. Heating season B. Cooling season C. Defrost periods D. Spring and fall seasonsThe indoor coil is called a condenser during the______season.Why is it important to have drainage for the outdoor unit?Which metering device is most efficient in heat pumps? A. A thermostatic expansion valve B. An automatic expansion valve C. A capillary tube D. An orifice or restrictorWhere is the only permanent suction line on a heat pump?What type of drier may be used in the liquid line of a heat pump?Where must a suction-line drier be placed in a heat pump after a motor burnout?What controls the heat pump to determine whether it is in the heating cycle or the cooling cycle?Can a heat pump switch from heating to cooling and from cooling to heating automatically?What must be done when frost and ice build up on the outdoor coil of a heat pump?True or False: All heat pumps are practical anywhere in the United States. Explain your answer.Why are scroll compressors more efficient than reciprocating compressors?Describe why variable-speed compressor motors are more efficient than single-speed motors in heat pump systems.Geothermal heat pumps, or water-source heat pumps, are classified as either _____loop or _____loop systems.An important factor (or factors) involving water quality with regard to open-loop heat pump systems is(are) A. water temperature. B. water cleanliness. C. water volume in gpm. D. all of the above.Explain the ground loop or water loop of a closed-loop,geothermal heat pump system.Explain the refrigerant loop of a closed-loop, geothermalheat pump system.The__________loop is used to distribute heated or cooled air to the building of a geothermal heat pump system.True or False: Domestic hot water can be heated with a geothermal heat pump system.7RQAntifreeze solutions that can be used in the ground loop of a closed-loop geothermal heat pump system can be A. alcohol. B. salts. C. glycols. D. all of the above.What is the main difference between a copper and a cupronickel coaxial heat exchanger, and where is each used?A(n) ______well draws water from the top of thewater column, circulates it through the heat pump, and then returns the water to the bottom of the water column.Which of the following is a process in which a cement-like material is injected between the well casing and the hole drilled for the well? A. Grouting B. Cementing C. Sealing D. SeparatingThe function of the pressure tank in an open-loop, geo-thermal heat pump well system is to prevent the well pump from _____.If 14 gpm of water is flowing through an open-loop heat pump with a temperature difference of 7F, how much heat in Btu/h is being absorbed or rejected in the heat pump? Show all work and units.Explain the operation/purpose of the buffer tank on a water-to-water heat pump system.How will oversizing the buffer tank on a water-to-water heat pump system affect the run time of the system?Explain why a waterless, earth-coupled, closed-loop geo-thermal heat pump system is more efficient than a conventional closed-loop geothermal heat pump system.Explain how refrigerant and oil leakage are found in a waterless, earth-coupled, closed-loop geothermal heat pump system.What kind of material is used in the waterless ground loop in a waterless, earth-coupled, closed-loop geothermal heat pump system?The typical temperature inside the fresh-food compartment in a domestic refrigerator is A. 25F to 30F. B. 30F to 35F. C. 35F to 40F. D. 40F to 45F.The operating condition for the single compressor in a household refrigerator is the lowest box temperature, which is typically A. 0F B. -20F C. 20F D. 40FWhen the air temperature in a domestic freezer is 0F, the plate-type evaporator temperature may be as low as A. -30F. B. -12F. C. -6F. D. 0F.Typical head pressures should correspond to a condensing temperature_________ F higher than room temperature at design operating conditions. A. 5-10 B. 10-15 C. 20-35 D. 35-45Using the temperature/pressure chart in Unit 3, the psigfor R-134a at —5F would be ____.Using the pressure/temperature chart in Unit 3, the psig for R-134a at 100F would be______.If a forced-draft evaporator fan motor is wired in parallel with the compressor, when will it run?Frost accumulates on the evaporators of forced-draft refrigerators because A. they are generally located within a house. B. they are generally located in high-humidity areas. C. they are low-temperature appliances. D. there is a heat exchange with the suction line.The defrost cycle in a domestic refrigerator may be terminated by two methods: ___and___.10RQWhat are the two types of evaporators found in house-hold refrigerators?Refrigerators currently being manufactured in the United States are using______as their refrigerant.Condensers in these refrigerators are all_______cooled.Home freezers are air-cooled and may have _____or______type condensers.Induced-draft condensers are typically used with units that have _____defrost. A. automatic B. manualThe capillary tube metering device is usually fastened to the______for heat exchange. A. suction line B. compressor discharge line C. liquid line17RQIf the compressor has liquid refrigerant returning to it, it will______on the side. A. be hot B. be warmSome freezers may have ______heaters to prevent sweat on the cabinet.Welded ______sealed compressors are normally used in household refrigerators.Special heaters called ______heaters are often locatedaround the doors to keep the door facing above the dew point temperature to avoid sweating. A. defrost B. condensate C. mullion or panel D. oil22RQ23RQThe adjustment device used for low atmospheric pressure conditions is called the _____ thermostatic adjustment control. A. positive temperature coefficient B. altitude C. dual-voltage D. condenser coil25RQA typical room air-conditioning unit has _____(one or two) fan motors.2RQThe line that carries refrigerant into the metering device is the A. suction line. B. discharge line. C. liquid line.4RQ5RQ6RQ7RQ8RQ9RQ10RQ11RQ12RQDescribe the operation of the exhaust and fresh-air control.Why should gauges be installed only after there is evidence that they are needed?15RQ16RQDuring the heat pump heating cycle, the hot gas from the compressor discharge line is directed to the A. indoor coil. B. outdoor coil.What are two methods used to evaporate condensate from the evaporator?When a chiller is used, the secondary refrigerant that circulates in the building is _____.What are the two basic categories of chillers?Three types of compressors are used for chillers: _____, ______, and ______.Blocked suction cylinder unloading is accomplished by A. keeping the suction valve closed. B. closing the discharge. C. closing the suction service valve. D. using a device in the low-pressure side of the system to close it off.True or False: The capacity control for a screw compressor is accomplished with cylinder unloading.Which of the following methods are used to controlcapacity of a centrifugal compressor? A. Cylinder unloading B. Prorogation vane control C. Blocked discharge D. High- to low-side bypassDescribe a direct-expansion versus a flooded evaporator.What is the purpose of multiple passes in a chiller evaporator?The approach temperature for the evaporator is A. the difference between the suction and head pressures converted to temperature. B. the difference between the refrigerant boiling temperature and the suction-line temperature. C. the difference between the refrigerant boiling temperature and the inlet water temperature. D. the difference between the refrigerant boiling temperature and the leaving-water temperature.What type of water-cooled condenser is used in large chillers?The compressor used in low-pressure chillers is the A. centrifugal. B. screw. C. rotary. D. reciprocating.List the types of metering devices used with high-pressure chillers.The subcooling temperature in a condenser can be measured by taking the difference between the A. suction pressure converted to temperature and the boiling refrigerant. B. boiling temperature and the condensing temperature. C. condensing temperature and the leaving-refrigerant temperature. D). condensing temperature and the entering-refrigerant temperature.What causes a surge in a centrifugal chiller?Why is it important to keep an operating log on a chiller?Which of the following metering devices is used in low-pressure chillers? A. A low- or high-side float B. A capillary tube C. An automatic expansion valve D. A thermostatic expansion valveThe purge unit in a low-pressure chiller removes A. overcharge of refrigerant. B. excess oil. C.condensable refrigerant. D. noncondensables.In an absorption chiller, _______is used to create the difference in pressures.The types of energy used to power a typical absorption refrigeration machine are____ and_____.True or False: Some absorption machines are directly fired with gas or oil.What is the common refrigerant used in absorption refrigeration machines?How is capacity control accomplished with a steam-driven absorption refrigeration machine?True or False: Single-phase induction, run-repulsion start motors are used with centrifugal machines.Describe how a wye-delta is started and runs.Why is it important to have phase protection for large motors?What is the purpose of the cooling tower in a water-cooled system?The typical difference in temperature between the cooling tower water supplied to the condenser and the out-door wet-bulb temperature is _____F.3RQ4RQ5RQWhy should cooling towers be constructed with fireproof materials?7RQ8RQ9RQ10RQVortexing in a cooling tower occurs in the A. inlet piping. B. basin of the tower. C. outlet piping. D. pump discharge.12RQ13RQWhat is the component that is installed between the pump shaft and the motor shaft?15RQ16RQ17RQ18RQWhat is meant by encapsulation and explain how it applies to cooling towers.20RQExplain how a particle separator works in a cooling tower system.How does the compressor lubrication system differ for reciprocating and centrifugal compressors?True or False: Most reciprocating compressors have crankcase heaters.True or False: All reciprocating compressors start up fully loaded.Describe how a centrifugal compressor starts up at part load and then goes to full load.Describe how a centrifugal compressor starts up at part load and then goes to full load.When condenser tubes become fouled, they may be cleaned by A. using a steel brush. B. using a brass brush. C. using a chisel and hammer. D. running a mixture of sand and water through them.Describe what happens when an absorption chiller is operated when the cooling tower water is too cold.Which of the following is true regarding the refrigerant piping on a rooftop package unit?
A. The discharge and liquid lines must be field installed.
B. The suction and liquid lines must be field installed.
C. The discharge and suction lines must be field installed.
D. No refrigerant lines are field installed.
Which process would best represent the opposite of exhausting air from a system?
A. Cooling
B. Ventilating
C. Heating
D. Filtering
Mixed air is best described as the combination of
A. exhaust air and return air.
B. return air and outside air.
C. supply air and return air.
D. exhaust air and outside air.
Which of the following should be taken into account when selecting the location and position of a rooftop package unit? A. Possible snow accumulation B. Condenser air circulation C. Serviceability D. All of the aboveA bonded roof is one that has A. reinforced steel structural members. B. a written warranty or insurance policy. C. a leak-free rubber membrane. D. a slope of no more than 30 degrees.Properly installed roof curbs will reduce the chances of
A. leaks.
B. noise transmission.
C. Both A and B are correct.
D. Neither A nor B is correct.
When rigging a unit to the roof, what minimum number of installation crew members should be on hand, not including the crane operator?
A. 1
B. 2
C. 3
C. 4
What is the acceptable method for communicating with the crane operator while rigging a unit to the roof? A. Cell phones B. Walkie-talkies C. Hand signals D. Verbal communications9RQ10RQThe most efficient way to establish the best possible economizer position is to measure
A. the dry-bulb temperature of the return and outside airstreams.
B. the dry-bulb temperature of the return air and the enthalpy of the outside air.
C. the enthalpy of the return air and the dry-bulb temperature of the outside air.
D. the enthalpy of both the return air and the outside air.
Free-cooling can be accomplished if the
A. enthalpy of the return air is lower than the enthalpy of the outside air.
B. enthalpy of the outside air is lower than the enthalpy of the return air.
C. enthalpy of the return air is lower than the enthalpy of the supply air.
D. enthalpy of the return air is the same as the enthalpy of the outside air.
13RQ14RQExplain why the outside air damper is typically never completely closed, even when the outside air conditions are not adequate to provide free-cooling.Briefly explain the purpose of ASHRAE Standard 62.Explain the concept of demand control ventilation.Explain how carbon dioxide levels can be used to estimate the occupancy level in a particular area in a structure.
Describe the blowers used on VAV systems.A cooling-only VAV box has all of the following except a(n) A. damper. B. control module. C. reheat coil. D. air pressure sensor.Which of the following is true regarding a reheat water circuit that utilizes two-way modulating valves?
A. The water is always circulating and is not prone to coil freeze-up.
B. The flow rate is always constant through the reheat water circuit.
C. The pump must be able to vary its flow.
D. The reheat coil is equipped with a bypass pipe.
Variable refrigerant flow systems sense the ______and _____of the refrigerant to determine the optimal volume of refrigerant to circulate.The acronym PID stands for ______, _____, and ______.
Explain the main benefit of a heat-recovery VRF system.The pump on a dry cooler can direct water to either the tube-in-tube heat exchanger or the cooling coil with the aid of a A. two-way valve. B. three-way valve. C. four-way valve. D. five-way valve.During low ambient conditions, the space cooling bycooler provides A. operating the system compressors. B. pumping water to the tube-in-tube heat exchanger. C. pumping water to a cooling coil located in the airstream. D. de-energizing the blower in the air distribution system.