HVAC Pretest: BOMA Questions and Answers, Exams of Advanced Education

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HVAC PRETEST BOMA QUESTIONS

Two basic categories of chillers are the ___. a. Compression cycle and absorption b. purge and absorption c. absorption and lithium bromide d. purge and lithium bromide - a. Compression cycle and absorption The five requirements for comfort are proper temperature, humidity, filtration, _____, and ventilation. a. circulation b. velocity c. sq.ft. d. none of the above - a. circulation The primary function of an expansion device is to ____. a. produce a reduction in the pressure on the liquid refrigerant b. regulate the flow of refrigerant into the evaporator c. lower the boiling point of the refrigerant far enough below the temperature of the load to get the needed heat transfer rate d. all of the above - d. all of the above The wet-bulb depression is ____. a. the difference between the dry-bulb and wet-bulb temperatures b. the same as the wet-bulb temperatures c. the same as the dry-bulb temperatures d. when the air is saturated with moisture - a. the difference between the dry-bulb and wet-bulb temperatures The dew-point temperature is the ___. a. temperature when the air is saturated with moisture b. temperature when the moisture begins to condense out of the air c. difference between the dry-bulb and wet-bulb temperatures d. temperature of the air at 50% relative humidity - b. temperature when the moisture begins to condense out of the air How many Btus are required to change one pound of ice at 20°F to steam at 220°F? a. 1,304 Btu/h b. 2,608 Btu/h c. 6,520 Btu/h

d. 3,912 Btu/h - a. 1,304 Btu/h If an R-12 refrigeration system is operating with a 25.4 psig suction pressure, what is the evaporator superheat if the evaporator outlet temperature is 34 degrees F. a. 9°F b. 59°F c. 34°F d. 25°F - a. 9°F On an R-11 or R-123 system, the refrigerant removal process normally starts with the removal of ____. a. water b. liquid refrigerant c. vapor refrigerant d. oil - b. liquid refrigerant The condenser in a refrigeration system ___. a. desuperheats the vapor from the compressor b. condenses the vapor from the compressor c. subcools the liquid refrigerant before it leaves the condenser d. all of the above - d. all of the above The human body gives off heat by which of the following? a. convection b. radiation c. conduction d. all of the above - d. all of the above If the temperature remains constant and the volume that a gas occupies increases, the pressure will ____. a. decrease b. increase c. remain the same d. cannot be determined from the information given. - a. decrease Transformers are rated using ___. a. volt-amperes b. volt-ohms c. amperes-ohms d. volt-resistance - a. volt-amperes

Measuring velocity pressure in a duct indicates the ___. a. volume of air through a duct b. speed at which the air is moving c. pressure against the sides of the duct. d. weight of the air moving through the duct. - b. speed at which the air is moving A solid material exerts a pressure or force ___. a. in all directions b. downward only c. outward and downward d. outward only - b. downward only Pure water boils at a temperature of 212°F at which of the following standard conditions? a. 12.967psi b. 13.967psi c. 14.967psi d. 15.967psi - c. 14.967psi Which of the following would allow a system to operate more efficiently? a. condenser that had refrigerant leaving with 10° of subcooling b. condenser that had refrigerant leaving with 15° of subcooling c. condenser that had refrigerant leaving as 100% vapor d. condenser that had refrigerant leaving with 10°F of superheat - b. condenser that had refrigerant leaving with 15° of subcooling One watt of electrical energy is equal to ___. a. 3.1416 Btu b. 3.413 Btu c. 3.3416 Btu d. 3.3146 Btu - b. 3.413 Btu Rotary compressors are used primarily in ____. a. large industrial refrigeration and air conditioning systems b. residential air conditioning c. small commercial refrigeration units d. domestic refrigerators - d. domestic refrigerators

The water circuit in shell and coil and coil-type tube-in-a-tube condensers must be cleaned ____. a. by removing the end caps b. with a brush c. chemically d. by air pressure - c. chemically When a water regulating valve is used to control the head pressure of a water-cooled system, the valve's spring is acting against which pressure to modulate the water flow? a. head pressure of the system b. water pressure c. suction pressure d. atmospheric pressure. - a. head pressure of the system The standard atmospheric pressure at sea level is ___. a. 29.60" Hg b. 29.71" Hg c. 29.83" Hg d. 29.92" Hg - d. 29.92" Hg The steps to aggressively controlling the contamination of indoor air would involve ____. a. locating and eliminating the source of contamination b. providing adequate ventilation c. providing methods for cleaning the air d. all of the above - d. all of the above If the resistance against a propeller fan is doubled, the cfm output decreases, but the amperage draw of the motor ___. a. decreases b. increases c. stays the same d. overheats the motor - b. increases Which of the following represents a different temperature than the other three? a. 15°C b. 59°F c. 475°K d. 519°R - c. 475°K The best method of leak checking is when the refrigeration system is ____.

a. in a vacuum b. open to the atmosphere c. operating with all fans activated d. standing with dry nitrogen pressure of 150 psig in the system. - d. standing with dry nitrogen pressure of 150 psig in the system. Technician "A" says that if the air filter on an air-conditioning system is totally blocked with dirt, the amperage draw of the evaporator fan motor will go down. Technician "B" says that if you close down one supply register on a duct system, the volume of air feeding the other locations will increase slightly. Which of the following statements is correct? a. Technician "A" is correct. Technician "B" is correct. b. Technician "A" is correct. Technician "B" is incorrect. c. Technician "A" is incorrect. Technician "B" is correct. d. Technician "A" is incorrect. Technician "B" is incorrect. - a. Technician "A" is correct. Technician "B" is correct. The refrigerant in a refrigeration system changes state in the ____. a. condenser and compressor b. compressor and expansion device c. expansion device and evaporator d. condenser and evaporator - d. condenser and evaporator The amount of heat needed to change the temperature of a substance will vary with the type of substance. This heat quality is called the ___ of the substance. a. sensible heat b. specific heat c. latent heat d. relative heat - b. specific heat Oil pressure safety controls measure the difference in pressure between the ___. a. oil pump inlet and discharge pressures b. oil pump discharge pressure and compressor head pressure c. oil pump inlet pressure and compressor suction pressure d. oil pump discharge pressure and compressor crankcase pressure - d. oil pump discharge pressure and compressor crankcase pressure On a 95°F day, the R-22 refrigerant pressure on the high side should be about ____ psig. a. 182

b. 108 c. 297 d. 243 - d. 243 The pressure in a refrigeration system is changed in the ___. a. condenser and compressor b. compressor and expansion device c. expansion device and evaporator d. condenser and evaporator - b. compressor and expansion device If the resistance against a centrifugal blower is doubled, the cfm output decreases, and the amperage draw of the motor ___. a. decreases slightly b. increases slightly c. stays the same d. overheats the motor - a. decreases slightly If the suction pressure of a system is 60 psig and the oil pump outlet is 85 psig, what is the net oil pressure? a. 60 psig b. 25 psig c. 85 psig d. 145 psig - b. 25 psig Noncodensable gases ___. a. are desirable in a refrigeration system b. are undesirable in a refrigeration system c. condense readily under normal atmospheric conditions d. help in pulling a vaccum - b. are undesirable in a refrigeration system If a high temperature evaporator is forming ice, which of the following is a possible problem? a. evaporator fan not running b. compressor not running c. condenser fan not running d. no problem, ice formation normal - a. evaporator fan not running The evaporator in a refrigeration system ___. a. reduces the boiling point of the refrigerant b. condenses the refrigerant

c. absorbs heat from the product to be cooled d. compresses the refrigerant vapor - c. absorbs heat from the product to be cooled An example of a power consuming device would be a ____ while an example of a non- power consuming device would be a ___. a. single-pole single-throw switch, light bulb b. light bulb, electric motor c. electric motor, light bulb d. light bulb, single-pole single-throw switch - d. light bulb, single-pole single-throw switch A liquid material exerts a pressure or force ____. a. in all directions b. downward only c. outward and downward d. outward only - c. outward and downward When moisture is present in a refrigeration system, it will react with the refrigerant and the oil to form ___. a. carbon dioxide b. acid c. carbon monoxide d. all of the above - b. acid A direct expansion-type evaporator is also called a ___. a. flooded evaporator b. dry-type evaporator c. multi-circiut evaporator d. stamped evaporator - b. dry-type evaporator The generalized comfort chart can be used as a basis to ____. a. determine combinations of temperature and humidity to produce comfort in summer and winter b. study air and its properties c. determine the amount of fresh air make up necessary for comfort d. none of the above - a. determine combinations of temperature and humidity to produce comfort in summer and winter The condenser ____. a. rejects the heat from the refrigerant

b. controls the refrigerant flow throughout the system c. adds superheat to the refrigerant d. all of the above - a. rejects the heat from the refrigerant Positive displacement compressors have crankcase heat to ____. a. preheat the chilled water for better efficiency b. prevent refrigerant migration to the compressor c. preheat the compressor bearings for longer wear d. minimize condenser subcooling - b. prevent refrigerant migration to the compressor If the power element of a TX valve loses its charge, the ____. a. coil will flood enough to feed liquid refrigerant out of the coil b. valve will get cold enough to create farost on the body of the valve c. refrigerant flow through the various circuits of the coil will become unbalanced d. refrigerant flow to the coil will stop - d. A normally operating water-cooled condenser is operating with a 10° differential between water in and water out. If the amount of 85°F water going through the condenser is reduced, which of the following is a possible temperature of the water leaving the condenser? a. 75°F b. 0°F c. 95°F d. 105°F - d. 105°F High temperature refrigeration is that produced by ____. a. heat from a furnace b. an air-conditioning system c. the vegetable cooling system of a refrigerator d. the freezer section of a refrigerator - b.an air-conditioning system Of the following choices, the warmest temperature is ____ while the coldest temperature is ____. a. 20°C b. 303°K c. 501°R d. 77°F - b. 303°K Infiltration is the term used when referring to the air entering a structure ____. a. through an air make-up unit

b. around doors and windows c. through ventilation d.because of street traffic - b.around doors and windows A micron gauge is used to measure ____. a. atmospheric pressures at high altitudes b. atmospheric pressures at sea level c. absolute pressures below 1 mm Hg d. high pressure in a refrigeration system - c.absolute pressures below 1 mm Hg The compressors used in low pressure chillers are the ____ type. a. reciprocating b. scroll c. screw d. centrifugal - d. centrifugal Most of the heat energy in the suction vapor entering the compressor is ____. a. heat of compression b. sensible heat c. latent heat d. defrost heat - c. latent heat The __ laws of thermodynamics that apply to heating and airconditioning. a. 2 b. 3 c. 1 d. 4 - a. 2 If the thermal bulb assembly develops a leak, what will occur? a. All of the system's refrigerant will leak out. b. The bulb pressure will reduce and the valve will close. c. The valve will open to allow more refrigerant to flow. d. It will have no effect on system operation. - b.The bulb pressure will reduce and the valve will close. The capacity of an evaporator is affected by ____. a. the saturation pressure of the low side of the system b. the saturation pressure of the high side of the system c. the amount of evaporator superheat d. all of the above - d. all of the above

The heat required for off-cycle defrost is obtained from ____. a. supplemental electric heat when the system is shut down b. hot gas when the system is operating c. the space temperature when the compressor is off d. hot liquid from the compressor - c. the space temperature when the compressor is off A motor's speed is determined by ____. a. size b. voltage c. amperage d.number of motor poles - d. number of motor poles By design, which of the following air ducts will allow 250 cfm to flow with a velocity of 500 ft/min? a. 8" x 9" b. 16" x 9" c. 10" x 9" d. none of these - a. 8" x 9" Which of the following refrigerants has the lowest boiling temperatures at atmospheric pressure? a. R- b. R- c. R-134a d.R-502 - d.R- The unit used to measure electrical power is the ____. a. volt b. ampere c. watt d.ohm - c. watt When a Capacitor Start, Capacitor Run (CSCR) motor initially starts, what is the total capacitance acting on the motor? (Assume the run capacitor is 5 microfarads and the start capacitor is 20 microfarads.) a. 5 microfarads b. 4 microfarads c. 20 microfarads d 25 microfarads - d 25 microfarads

The instrument to use to check for a short in the compressor motor winding is a(n) ____. a. ohmmeter b. ammeter c. voltmeter d.milliammeter - a.ohmmeter Comfort can be described as the gentle balance between ____. a. air cleanliness, air movement, temperature, and humidity b. air velocity, air cleanliness, humidity, and air movement c. air speed, air velocity, temperature, and humidity d. acceleration, air cleanliness, filtration, and humidity - a.air cleanliness, air movement, temperature, and humidity A current magnetic relay opens and closes its contacts based on the ____. a. current in the start winding b. voltage across the start winding c. voltage across the run winding d. current in the run winding - d. current in the run winding A typical evaporator operating temperature in an air-conditioning system is ____ a. 40°F b. 55°F c. 75°F d. 200°F - a.40°F When a refrigerant enters the compressor, it is a ____ and when it leaves the compressor, it is a ____. a. low pressure low temperature superheated vapor, high pressure high temperature superheated vapor b. low pressure low temperature superheated vapor, low pressure low temperature subcooled vapor c. high pressure superheated vapor, low pressure superheated vapor d.low pressure low temperature subcooled liquid, high pressure high temperature superheated vapor - a.low pressure low temperature superheated vapor, high pressure high temperature superheated vapor Which of the following is typically measured with an inclined water manometer? a. static pressure in a duct system

b. pressure in a refrigeration system c. manifold pressure in a gas fired furnace d. nozzle pressure of an oil burner - a.static pressure in a duct system The volume of gas varies inversely with the absolute pressure, provided the temperature remains constant. This is called ____. a. Charles' Law b. Tom's Law c. Boyle's Law d. Dalton's Law - c Boyle's Law A control can be which of the following? a. electrical b. mechanical c. electrical and mechanical d. all of the above - d. all of the above The purpose of an externally equalized thermostatic expansion valve is to ____. a. compensate for excessive evaporator pressure drop b. allow system to equalize faster c. prevent the expansion valve from frosting up d. allow refrigerant to expand in the compressor - a. compensate for excessive evaporator pressure drop The pressure in a duct system is measured in: a. psig b. psia c. " Hg d. " WC - d " WC If the compression ratio of a system with a reciprocating compressor decreases, the amount of refrigerant pumped by the compressor ____. a. will increase b. will decrease c. will remain the same d. cannot be determined - a will increase The approach of a cooling tower is the ____. a. difference between the entering and leaving wet-bulb temperatures

b. number of degrees the water is cooled in the tower c. difference in temperature between the entering air wet-bulb temperature and the sump water temperature d. difference in temperature between the entering air web-bulb temperature and the water entering the tower - c difference in temperature between the entering air wet-bulb temperature and the sump water temperature The screw-type compressor is used primarily in ____. a. large industrial refrigeration and air-conditioning systems b. residential air conditioning c. small commercial refrigeration units d. domestic refrigerators - a. large industrial refrigeration and air-conditioning systems At what location or locations in a refrigeration system does the saturation pressure correspond to the saturation temperature? a. compressor and evaporator b. evaporator and condenser c. condenser and expansion device d. compressor - b evaporator and condenser A split-phase motor can use a ____ to energize and de-energize the start winding. a. potential relay b. current relay c. centrifugal switch d. all of the above - d. all of the above Temperature is an indication of the ____. a. amount of heat in a material b. density of the material c. amount of molecular activity in the material d. weight of the total mass of the material - c. amount of molecular activity in the material The compressor motor and condenser fan motor are wired in ____. a. parallel b. series c. parallel/series d. with minimum wire length - a. parallel How many watts of electrical power are equal to 1 horsepower?

a. 33000 b. 15000 c. 746 d. 660 - c. 746 How many Btu's are required to change five pounds of ice at 20°F to steam at 220°F? a. 1,304 Btu/h b. 2,608 Btu/h c. 6,520 Btu/h d. 3,912 Btu/h - c. 6,520 Btu/h Refrigeration can be described as ____. a. the process of making products cold b. the process of introducing heat to a location where it is not wanted c. the process of removing heat from a place where it is not wanted to a place where it makes little or no difference d. none of the above - c. the process of removing heat from a place where it is not wanted to a place where it makes little or no difference Reciprocating compressors have ____. a. a piston and cylinder b. two scrolls that mesh together c. a rotor to compress the refrigerant d. a large fan compressor component - a. a piston and cylinder When a system with a water-cooled condenser cycles off, the water regulating valve should ____. a. remain open during the off cycle b. close, since the head pressure is lower c. open all the way to remove any residual heat d. re-calibrate itself to maintain the new lower head pressure - b. close, since the head pressure is lower Where would a water regulating valve that is controlling head pressure be installed? a. water circuit at inlet of condenser b. discharge line at outlet of compressor c. suction line d. liquid line close to the condenser - a. water circuit at inlet of condenser The evaporator of a chiller can be used to absorb heat from ____.

a. water b. a solution of water and polyethylene glycol c. the refrigerant d. both a and b - d. both a and b At a constant pressure, the volume of a gas varies as to the absolute temperature and at a constant volume the pressure of the gas varies directly with the absolute temperature. This is known as ____. a. Charles' Law b. Tom's Law c. Boyle's Law d. Dalton's Law - a. Charles' Law A helicopter is lifting an 800-pound unit at a rate of 200 feet per minute. How many horsepower of work energy is the helicopter using in the process? a. 3.863 hp b. 4.517 hp c. 4.848 hp d. 5.209 hp - c. 4.848 hp Centrifugal chillers range in size from ____ tons. a. 10 to 50 b. 10 to 80 c. 50 to 500 d. 100 to 10,000 - d. 100 to 10, If an R-12 refrigeration system has its air-cooled condensing unit on a 100°F roof and the condenser outlet temperature (refrigerant) is 115°F, with how much subcooling is the condenser operating? a. 30°F b. 15°F c. 100°F d. 130°F - b. 15°F A vapor material exerts a pressure or force ____. a. in all directions b. downward only c. outward and downward d. outward only - a. in all directions What happens when room temperature soda is poured into a glass of ice?

a. The ice gets colder. b. The ice melts because it is giving up the "cold" to the soda. c. The ice melts because it is absorbing heat from the soda. d. The ice melts because the soda is colder than the ice. - c. The ice melts because it is absorbing heat from the soda. The controller for a humidifier, a humidistat, has a power element that is ____ sensitive. a. moisture b. light c. infrared d.temperature - a. moisture Which of the following represents the lowest vacuum? a. 10 psia b. 5" Hg VAC c. 5 psig d.1000 microns - d. 1000 microns The compressor in a refrigeration system ____. a. raises the boiling point of the refrigerant b. pumps the refrigerant throughout the system c. both a and b d.none of the above - b. pumps the refrigerant throughout the system To control ice build-up on a heat pump outdoor coil in the heating cycle, a ____ is used. a. toggle switch b. pressure differential switch c. push button switch d.sail switch - b. pressure differential switch A split-phase has a ____ winding and a ____ winding. a. start, run b. start, common c. common, run d. run, common - a. start, run The total pressure of a confined mixture of gases is the sum of the pressures of each of the gases in the mixture. This is known as ____. a. Charles' Law

b. Tom's Law c. Boyle's Law d. Dalton's Law - d. Dalton's Law PSIG indicates ____. a. pounds per square inch absolute gravity b. pounds per square inch absolute gage c. pounds per square inch of pressure absolute d. pounds per square inch of gravity - b. pounds per square inch absolute gage A typical superheat for an evaporator operating under normal conditions would be ____. a. 14 to 16°F b. 4 to 6°F c. 8 to 12°F d. 6 to 8°F - c. 8 to 12°F A ton of refrigeration is equal to ____. a. 1 ton of ice b. 288000 Btu/24-hr. c. 144 Btu/hr. d. 12000 Btu/min. - b. 288000 Btu/24-hr. The refrigerant in a condenser in a refrigeration system ____. a. absorbs heat b. gives up heat c. changes to a vapor d. is under lower pressure than the evaporator - b. gives up heat