HVAC Air Conditioning Esco 2024-2025 Exam with Correct Answers, Exams of Refrigeration and Air Conditioning

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HVAC Air Condition Esco 2024-

exam with correct answers

Heat which causes a change in temperature of a substance is called - correct answer -Sensible Heat Heat added to a substance without a rise in temperature is called - correct answer -Latent Heat Heat added to refrigerant in a vapor state after the evaporation process is called - correct answer - Superheat A scroll compressor moved refrigerant by means of - correct answer -Involute spirals The movement of heat by way of fluid is called - correct answer -Convection The movement of heat through a solid object is called - correct answer -Conduction The standard unit for measuring the quantity of heat in a substance - correct answer -British Thermal Unit A refrigerant gives up heat when it - correct answer -Condenses Why must refrigerant in the suction line be slightly warmer than the saturation temperature? - correct answer -Prevent liquid slugging of compressor It is desirable for refrigerant in the suction line to be slightly superheated in order to - correct answer - Insure liquid refrigerant does not enter the compressor A mechanical shaft seal is necessary on - correct answer -Semi-hermetic compressor Liquid slugging is - correct answer -Liquid refrigerant in the compressor clearance space

The clearance space in a reciprocating compressor - correct answer -Varies depending on compressor speed Which of the following types of air conditioning compressors is most energy efficient - correct answer - Centrifugal Which of the following represent the right order for the functions of a condenser? - correct answer -De- superheat, condenses, sub-cools Refrigerant R-134a vapor enters the compressor at 124 psig, 100°f. It leaves as a liquid from the condenser sub-cooled 20°f, and the pressure will approximately - correct answer -18.4 psig There are 3 basic types of condensers, the air cooled, the water cooled, and the _______ cooled - correct answer -Evaporative 10 lbs. of refrigerant passing through a water cooled condenser will lose 20 BTU's of heat per lb. If 10 lbs. of water passes through the condenser with an entering temperature of 80°f. The temperature of the water leaving the condenser is - correct answer -100°f The heat removed from the refrigerant by the condenser is - correct answer -Both sensible and latent heat An energy recovery ventilator is - correct answer -An air to air heat exchanger to recover heat Which of the following can NOT be used as a low ambient temperature control? - correct answer - Crankcase regulating valves The state of refrigeration in the suction line should be - correct answer -Low pressure/ low temperature vapor The state of refrigerant entering the condenser is - correct answer -High pressure/ highly superheated vapor

The evaporator - correct answer -Transfers heat from the refrigerated space to the refrigerant Which of the following is not a thermodynamic property of refrigerant - correct answer -Flammability The sequential order of steps in the vapor-compression process are - correct answer -Compression, condensation, expansion, vaporization If a 30 pound container of R-410A refrigerant has been stored over night at 70°F, the pressure in the cylinder should be approximately - correct answer -201 psig Fan airflow pressures are usually measured in - correct answer -Inches of water column (WC) Zero psig is - correct answer -The same as atmospheric pressure The temperature at which moisture will start to condense from the air is - correct answer -Dew point temperature A compound pressure gauge measures - correct answer -Pressure and vacuum When testing the efficiency of an air cooled condenser, the refrigerant condensing temperature should be no more than ______ higher than the entering air temperature - correct answer -30°f When testing the efficiency of a water cooled condenser, the refrigerant condensing temperature should be approximately _______ higher than the entering air temperature - correct answer -10°f The first function a condenser must perform is to _______ the refrigerant before condensing can occur - correct answer -Superheat A thermostatic expansion valve is designed to maintain - correct answer -Constant evaporator superheat

The thermostatic expansion valve has three operating pressures - correct answer -Evaporator pressure, spring pressure & sensing bulb pressure When mounting a thermostatic expansion valve, the temperature of the evaporator outlet will usually be - correct answer -Warmer than the evaporator inlet An automatic expansion valve is best suited - correct answer -When the system load remains fairly constant The automatic expansion valve is designed to maintain - correct answer -Constant evaporator pressure Which of the following is not true of a capillary metering device - correct answer -They maintain constant evaporator temperature A decrease in superheat causes the thermostatic expansion valve begins to - correct answer -Close A rise in evaporator pressure causes the automatic expansion valve to begin to - correct answer -Close A thermal-electric (solid state) expansion valve is controlled by - correct answer -NTC Thermistor In a direct expansion (DX) evaporator system, the refrigerant enters the evaporator as - correct answer - Mixture of liquid with some flash gas In the evaporator - correct answer -Latent heat is transferred from the refrigerated space to the refrigerant A liquid line filter drier should be placed between the - correct answer -Condenser and metering device The only way to minimize flash gas is by - correct answer -Sub-cooling the liquid refrigerant entering the metering device closer to the evaporator temperature

A liquid receiver is used to - correct answer -Store liquid refrigerant An accumulator is used to - correct answer -Prevent liquid refrigerant from reaching the compressor A sight glass would normally be located - correct answer -In the liquid line, before the metering device Bubbles in the sight glass could be an indication of - correct answer -Low compressor capacity The oil separator is installed in the - correct answer -Discharge line Which of the following is true of a solenoid valve in a pump down system - correct answer -It is located before the metering device The purpose of an evaporator pressure regulating valve is to - correct answer -Prevent evaporator pressure from falling A liquid-to-suction heat exchanger is often used to - correct answer -Increase liquid sub cooling The oil pressure safety switch is operated by - correct answer -The difference between crankcase pressure and oil pressure A low pressure cut off switch is used to - correct answer -Establish minimum operating pressure in the evaporator A partially iced over evaporator can be caused by - correct answer -An undercharge _________ can be caused for leak detection with all high pressure refrigerants - correct answer -Soap bubbles The flow rate of a TXV used in R410A systems as compared to R22 system is - correct answer - Approximately 15% lower

When using an electric leak detector, the sensing probe - correct answer -Should be moved approximately 1 inch every second Moisture in the refrigeration system will cause - correct answer -Compressor failure In order to remove as much moisture as from a system - correct answer -Triple evacuate the system to 500 microns with a deep vacuum pump What kind of gauge is used to measure microns - correct answer -An electronic vacuum gauge Water will vaporize at _______ temperature in a 28 in hg vacuum - correct answer -208 degrees F After a system has been opened and the compressor changed, the service technician must - correct answer -Replace the filter drier, leak check, evacuate, and charge Back seating a two way solenoid valve results in - correct answer -Closed service port with normal system flow Before vapor/ compression system is opened for service - correct answer -The refrigerant must be recovered using approved equipment The R410A compound gauge reads 124 psig and the suction line temperature at the condensing unit is 54°f. What is the operating superheat? - correct answer -11°F When topping off an operating system containing a blended refrigerant - correct answer -Introduce the refrigerant as a liquid into the low side using a throttle valve A partially clogged capillary tube metering device can cause - correct answer -A starved evaporator The R134a high pressure gauge reads 146 psig and the liquid line temperature at the condensing unit is 95°f what is the operating subcooling? - correct answer -15°f

An overcharge off refrigerant will cause - correct answer -Increased head pressure A drain trap should be installed on a split system when the - correct answer -Air handler drain is on the negative side A customer complains that their air conditioning system is running constantly but not cooling enough. The suction line is very cold and the compressor is sweating. The most likely cause is - correct answer -A restriction of the return air or a dirty evaporator What is the generally accepted range for evaporator air flow in CFMs per ton of residential air conditioning? - correct answer -350 to 450 A customer reports that their residential split system had a compressor replaced last week by another service company. Now the unit is not cooling properly. When you arrive and inspect the unit, you find that the evaporator seems to be starved of refrigerant. On examining the condensing unit, you find that the liquid line is seating where it leaves the drier. This most likely the result of - correct answer -Debris from the burned out compressor has clogged the drier. The temperature rise method for determining air flow is - correct answer -CFM = BTU / (1.08 x Delta h) What is recommended residential indoor relative humidity for summer? - correct answer -50% An inefficient compressor is usually indicated by ________ head pressure and _________ suction pressure - correct answer -Lower than normal/ higher than normal Which is not a symptom of a hermetic system that is low on refrigerant? - correct answer -High head pressure Frost on the suction line indicates - correct answer -That the temperature is below the dew point and below 32°f

An increase in head pressure causes _________ refrigerant to flow through a capillary tube - correct answer -More With an automatic expansion valve, an increase in evaporator load will cause the - correct answer - Automatic expansion valve to close When a TEV or capillary tube is used as a metering device, a low refrigerant charge will cause - correct answer -Low head pressure What is the maximum operating pressure setting for an acetylene torch? - correct answer -15 psig When connecting copper to steel, the recommended brazing filler alloy is a - correct answer -45 percent silver alloy Solid contaminants, such as sludge and carbon, from a severe hermetic compressor motor burn out are best - correct answer -By flushing the system and then installing filter/ driers in both the liquid and suction lines If the cut-off plate is removed from a blower assembly, how would this affect blower performance? - correct answer -It would reduce air flow At a residential service call "no cooling" complaint, the service technician finds the unit to be completely out of refrigerant the technician decides to use a trace amount of refrigerant and _________ in order to pressurize the system - correct answer -An inert gas A technician has found an air conditioning system with a leak in the liquid line. After the line is repaired, the system is evacuated and properly recharged. When the system is started, the compressor is noisy and running hot. The most probable cause of noise is - correct answer -Low oil in the system An air conditioning system that is oversized can cause - correct answer -Inefficient dehumidification of the conditioned space

While troubleshooting a residential split system, the service technician finds low operating pressures and low system amperage draw. This could be an indication of - correct answer -Low airflow across the evaporator Air or other non-condensable gases in a capillary tube air conditioning system will cause these symptoms - correct answer -High suction pressure and high discharge pressure A refrigerant overcharge in a capillary tube air conditioning system will cause these symptoms - correct answer -High suction pressure and high discharge pressure A compressor unit that has a broken reed valve will cause these symptoms - correct answer -High suction pressure and low discharge pressure A low refrigerant charge in a air conditioning system will cause these symptoms - correct answer -Low suction pressure and low discharge pressure A TEV sensing bulb which becomes detached from the suction line will cause these symptoms - correct answer -High suction pressure and lower than normal discharge pressure A faulty condenser fan motor on a air conditioning system will cause these symptoms - correct answer - High suction pressure and high discharge pressure A dirty evaporator in a air conditioning system will cause these symptoms - correct answer -Low suction pressure and low discharge pressure