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Heat which causes a change in temperature of a substance is called ๐ธ๐ธ๐ธ : Sensible Heat Heat added to a substance without a rise in temperature is called ๐ธ๐ธ๐ธ : Latent Heat Heat added to refrigerant in a vapor state after the evaporation process is called ๐ธ๐ธ๐ธ : Superheat A scroll compressor moved refrigerant by means of ๐ธ๐ธ๐ธ : Involute spirals The movement of heat by way of fluid is called ๐ธ๐ธ๐ธ : Convection The movement of heat through a solid object is called ๐ธ๐ธ๐ธ : Conduction
The standard unit for measuring the quantity of heat in a substance ๐ธ๐ธ๐ธ : British Thermal Unit A refrigerant gives up heat when it ๐ธ๐ธ๐ธ : Condenses Why must refrigerant in the suction line be slightly warmer than the saturation temperature? ๐ธ๐ธ๐ธ : Prevent liquid slugging of compressor It is desirable for refrigerant in the suction line to be slightly superheated in order to ๐ธ๐ธ๐ธ : Insure liquid refrigerant does not enter the compressor A mechanical shaft seal is necessary on ๐ธ๐ธ๐ธ : Semi-hermetic compressor Liquid slugging is ๐ธ๐ธ๐ธ : Liquid refrigerant in the compressor clearance space The clearance space in a reciprocating compressor ๐ธ๐ธ๐ธ : Varies depending on compressor speed
๐ธ๐ธ๐ธ : An air to air heat exchanger to recover heat Which of the following can NOT be used as a low ambient temperature control? ๐ธ๐ธ๐ธ : Crankcase regulating valves The state of refrigeration in the suction line should be ๐ธ๐ธ๐ธ : Low pressure/ low temperature vapor The state of refrigerant entering the condenser is ๐ธ๐ธ๐ธ : High pressure/ highly superheated vapor The evaporator ๐ธ๐ธ๐ธ : Transfers heat from the refrigerated space to the refrigerant Which of the following is not a thermodynamic property of refrigerant ๐ธ๐ธ๐ธ : Flammability The sequential order of steps in the vapor-compression process are ๐ธ๐ธ๐ธ : Compression, condensation, expansion, vaporization If a 30 pound container of R-410A refrigerant has been stored over night at 70ยฐF, the pressure in the cylinder should be approximately
๐ธ๐ธ๐ธ : 201 psig Fan airflow pressures are usually measured in ๐ธ๐ธ๐ธ : Inches of water column (WC) Zero psig is ๐ธ๐ธ๐ธ : The same as atmospheric pressure The temperature at which moisture will start to condense from the air is ๐ธ๐ธ๐ธ : Dew point temperature A compound pressure gauge measures ๐ธ๐ธ๐ธ : 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 ๐ธ๐ธ๐ธ : 30ยฐf When testing the efficiency of a water cooled condenser, the refrigerant condensing temperature should be approximately _______ higher than the entering air temperature ๐ธ๐ธ๐ธ : 10ยฐf
A decrease in superheat causes the thermostatic expansion valve begins to ๐ธ๐ธ๐ธ : Close A rise in evaporator pressure causes the automatic expansion valve to begin to ๐ธ๐ธ๐ธ : Close A thermal-electric (solid state) expansion valve is controlled by ๐ธ๐ธ๐ธ : NTC Thermistor In a direct expansion (DX) evaporator system, the refrigerant enters the evaporator as ๐ธ๐ธ๐ธ : Mixture of liquid with some flash gas In the evaporator ๐ธ๐ธ๐ธ : Latent heat is transferred from the refrigerated space to the refrigerant A liquid line filter drier should be placed between the ๐ธ๐ธ๐ธ : Condenser and metering device The only way to minimize flash gas is by ๐ธ๐ธ๐ธ : Sub-cooling the liquid refrigerant entering the metering device closer to the evaporator temperature
A liquid receiver is used to ๐ธ๐ธ๐ธ : Store liquid refrigerant An accumulator is used to ๐ธ๐ธ๐ธ : Prevent liquid refrigerant from reaching the compressor A sight glass would normally be located ๐ธ๐ธ๐ธ : In the liquid line, before the metering device Bubbles in the sight glass could be an indication of ๐ธ๐ธ๐ธ : Low compressor capacity The oil separator is installed in the ๐ธ๐ธ๐ธ : Discharge line Which of the following is true of a solenoid valve in a pump down system ๐ธ๐ธ๐ธ : It is located before the metering device The purpose of an evaporator pressure regulating valve is to ๐ธ๐ธ๐ธ : Prevent evaporator pressure from falling
๐ธ๐ธ๐ธ : Compressor failure In order to remove as much moisture as from a system ๐ธ๐ธ๐ธ : Triple evacuate the system to 500 microns with a deep vacuum pump What kind of gauge is used to measure microns ๐ธ๐ธ๐ธ : An electronic vacuum gauge Water will vaporize at _______ temperature in a 28 in hg vacuum ๐ธ๐ธ๐ธ : 208 degrees F After a system has been opened and the compressor changed, the service technician must ๐ธ๐ธ๐ธ : Replace the filter drier, leak check, evacuate, and charge Back seating a two way solenoid valve results in ๐ธ๐ธ๐ธ : Closed service port with normal system flow Before vapor/ compression system is opened for service ๐ธ๐ธ๐ธ : 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 54ยฐf. What is the operating superheat? ๐ธ๐ธ๐ธ : 11ยฐF When topping off an operating system containing a blended refrigerant ๐ธ๐ธ๐ธ : Introduce the refrigerant as a liquid into the low side using a throttle valve A partially clogged capillary tube metering device can cause ๐ธ๐ธ๐ธ : A starved evaporator The R134a high pressure gauge reads 146 psig and the liquid line temperature at the condensing unit is 95ยฐf what is the operating subcooling? ๐ธ๐ธ๐ธ : 15ยฐf An overcharge off refrigerant will cause ๐ธ๐ธ๐ธ : Increased head pressure A drain trap should be installed on a split system when the ๐ธ๐ธ๐ธ : 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
Which is not a symptom of a hermetic system that is low on refrigerant? ๐ธ๐ธ๐ธ : High head pressure Frost on the suction line indicates ๐ธ๐ธ๐ธ : That the temperature is below the dew point and below 32ยฐf An increase in head pressure causes _________ refrigerant to flow through a capillary tube ๐ธ๐ธ๐ธ : More With an automatic expansion valve, an increase in evaporator load will cause the ๐ธ๐ธ๐ธ : Automatic expansion valve to close When a TEV or capillary tube is used as a metering device, a low refrigerant charge will cause ๐ธ๐ธ๐ธ : Low head pressure What is the maximum operating pressure setting for an acetylene torch? ๐ธ๐ธ๐ธ : 15 psig When connecting copper to steel, the recommended brazing filler alloy is a ๐ธ๐ธ๐ธ : 45 percent silver alloy
Solid contaminants, such as sludge and carbon, from a severe hermetic compressor motor burn out are best ๐ธ๐ธ๐ธ : 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? ๐ธ๐ธ๐ธ : 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 ๐ธ๐ธ๐ธ : 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 ๐ธ๐ธ๐ธ : Low oil in the system An air conditioning system that is oversized can cause ๐ธ๐ธ๐ธ : Inefficient dehumidification of the conditioned space
๐ธ๐ธ๐ธ : High suction pressure and high discharge pressure A dirty evaporator in a air conditioning system will cause these symptoms ๐ธ๐ธ๐ธ : Low suction pressure and low discharge pressure
