HVAC EXCELLENCE FINAL PAPER UPDATED EXAM
QUESTIONS AND SOLUTIONS RATED A+
✔✔Which of the following is the most important consideration in the selection of an
evaporator coil? Match the coil to the? - ✔✔condensing unit and the latent/sensible
loads
✔✔A mechanical shaft seal is necessary on a? - ✔✔open drive compressor
✔✔Liquid slugging is? - ✔✔liquid refrigerant in the compressor clearance space
✔✔Water will vaporize at _______ temperature in a 28 in Hg vacuum? - ✔✔100ºF
✔✔The clearance space in a reciprocation compressor? - ✔✔has an effect on
compressor capacity
✔✔Zero PSIA (pounds per square inch absolute) is? - ✔✔a pressure that cannot further
be reduced
✔✔A compressor that has a broken reed valve will cause these symptoms? - ✔✔high
suction pressure and low discharge pressure
✔✔When topping off an operating system containing a blended refrigerant? -
✔✔introduce the refrigerant as a liquid into the low side using a throttling valve
✔✔A TEV sensing bulb which becomes detached from the suction line will cause these
symptoms? - ✔✔high suction pressure and higher than normal discharge pressure
✔✔It is desirable for a refrigerant in the suction line to be slightly superheated in order
to? - ✔✔insure liquid refrigerant does not enter the compressor
✔✔The state of the refrigerant in the suction line should be? - ✔✔low pressure / low
temperature vapor
✔✔Heat which is added to a vapor after the change of state occurs is called? -
✔✔superheat
✔✔Before a vapor and compression system is opened for service? - ✔✔the refrigerant
must be recovered using approved equipment
✔✔The 410a compound gauge reads 124 psig and the suction line temperature at the
condensing unit is 54ºF. What is the operating system superheat? - ✔✔12ºF
, ✔✔When an TEV or capillary tube is used as a metering device, a low refrigerant
charge will cause? - ✔✔low head pressure
✔✔The movement of heat by way of fluid (or air) is called? - ✔✔convection
✔✔Fan airflow pressures are usually measured in? - ✔✔inches of water column (WC)
✔✔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 the
noise is? - ✔✔low oil in the system
✔✔The evaporator? - ✔✔transfers heat from the refrigerated space to the refrigerant
✔✔A refrigerant gives up heat when? - ✔✔it condenses
✔✔While troubleshooting a residential split system, the service technician finds low
operating pressures and low system amperage draw. This could be an indication of? -
✔✔low airflow across the evaporator
✔✔A rise in evaporator pressure causes the automatic expansion valve to begin to? -
✔✔close
✔✔The R 134a high pressure gauge reads 143psig and the liquid line temperature at
the condensing unit is 95ºF. What is the operating system subcooling? - ✔✔13ºF
✔✔Heat which causes a change in state of a material without a change in temperature
is called? - ✔✔latent heat
✔✔An increase in head pressure causes _____ refrigerant to flow through a capillary
tube. - ✔✔more
✔✔What is the maximum operating pressure setting for an acetylene torch? - ✔✔15
psig
✔✔A low pressure cut-off switch is used to? - ✔✔establish a minimum operating
pressure in the evaporator
✔✔What is the generally accepted range for evaporator air flow in CFMs per ton of
residential air conditioning? - ✔✔350 to 450
✔✔A sight glass would normally be located? - ✔✔in the liquid line before the metering
device
QUESTIONS AND SOLUTIONS RATED A+
✔✔Which of the following is the most important consideration in the selection of an
evaporator coil? Match the coil to the? - ✔✔condensing unit and the latent/sensible
loads
✔✔A mechanical shaft seal is necessary on a? - ✔✔open drive compressor
✔✔Liquid slugging is? - ✔✔liquid refrigerant in the compressor clearance space
✔✔Water will vaporize at _______ temperature in a 28 in Hg vacuum? - ✔✔100ºF
✔✔The clearance space in a reciprocation compressor? - ✔✔has an effect on
compressor capacity
✔✔Zero PSIA (pounds per square inch absolute) is? - ✔✔a pressure that cannot further
be reduced
✔✔A compressor that has a broken reed valve will cause these symptoms? - ✔✔high
suction pressure and low discharge pressure
✔✔When topping off an operating system containing a blended refrigerant? -
✔✔introduce the refrigerant as a liquid into the low side using a throttling valve
✔✔A TEV sensing bulb which becomes detached from the suction line will cause these
symptoms? - ✔✔high suction pressure and higher than normal discharge pressure
✔✔It is desirable for a refrigerant in the suction line to be slightly superheated in order
to? - ✔✔insure liquid refrigerant does not enter the compressor
✔✔The state of the refrigerant in the suction line should be? - ✔✔low pressure / low
temperature vapor
✔✔Heat which is added to a vapor after the change of state occurs is called? -
✔✔superheat
✔✔Before a vapor and compression system is opened for service? - ✔✔the refrigerant
must be recovered using approved equipment
✔✔The 410a compound gauge reads 124 psig and the suction line temperature at the
condensing unit is 54ºF. What is the operating system superheat? - ✔✔12ºF
, ✔✔When an TEV or capillary tube is used as a metering device, a low refrigerant
charge will cause? - ✔✔low head pressure
✔✔The movement of heat by way of fluid (or air) is called? - ✔✔convection
✔✔Fan airflow pressures are usually measured in? - ✔✔inches of water column (WC)
✔✔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 the
noise is? - ✔✔low oil in the system
✔✔The evaporator? - ✔✔transfers heat from the refrigerated space to the refrigerant
✔✔A refrigerant gives up heat when? - ✔✔it condenses
✔✔While troubleshooting a residential split system, the service technician finds low
operating pressures and low system amperage draw. This could be an indication of? -
✔✔low airflow across the evaporator
✔✔A rise in evaporator pressure causes the automatic expansion valve to begin to? -
✔✔close
✔✔The R 134a high pressure gauge reads 143psig and the liquid line temperature at
the condensing unit is 95ºF. What is the operating system subcooling? - ✔✔13ºF
✔✔Heat which causes a change in state of a material without a change in temperature
is called? - ✔✔latent heat
✔✔An increase in head pressure causes _____ refrigerant to flow through a capillary
tube. - ✔✔more
✔✔What is the maximum operating pressure setting for an acetylene torch? - ✔✔15
psig
✔✔A low pressure cut-off switch is used to? - ✔✔establish a minimum operating
pressure in the evaporator
✔✔What is the generally accepted range for evaporator air flow in CFMs per ton of
residential air conditioning? - ✔✔350 to 450
✔✔A sight glass would normally be located? - ✔✔in the liquid line before the metering
device
