CFESA Refrigeration Chapter 6
What is the function of a metering device - answerTo lower the pressure of the
refrigerant and therefore the temperature of the refrigerant entering the evaporator
What varies the capacity of the cap Tube - answerThe diameter and length
What determines the size or capacity of a metering device needed - answerThe
capacity of the compressor at the evaporator temperature
What are the advantages to a cap tube - answerSimple and inexpensive
What are the disadvantages to a cap tube - answerEasily restricted with some newer
refrigerant cannot adjust flow of refrigerant in high demand. Periods
Cap Tubes are most suited to be used on what type of equipment - answerStorage
boxes
What usually causes cap tubes to fail - answerPartial restrictions from pollutants in the
system cracks or breaks from vibration
How can you tell if a cap tube system is under charged - answerYou will have high
superheat, low sub cooling and low capacity for cooling
How can you tell if a cap tube system is overcharged - answerHigher than normal head
pressure,high sub cooling, and lower superheat resulting in possible refrigerant flooding
back to the compressor
What happens if cap tube system is under heavy load - answerTemperature recovery is
very slow since the cap Tube can only feed through a constant amount of refrigerant,
based on the minimum load that exists as the box nears it set temperature
What does a critically charged system mean - answerIt means that the system requires
an exact charge to operate efficiently and properly
Can you charge a cap tube system by head pressure alone - answerNo
Can you charge a cap tube system By superheat - answerYes but only if you wait until
the box has almost reached its operating temperature
What is the function of a metering device - answerTo lower the pressure of the
refrigerant and therefore the temperature of the refrigerant entering the evaporator
What varies the capacity of the cap Tube - answerThe diameter and length
What determines the size or capacity of a metering device needed - answerThe
capacity of the compressor at the evaporator temperature
What are the advantages to a cap tube - answerSimple and inexpensive
What are the disadvantages to a cap tube - answerEasily restricted with some newer
refrigerant cannot adjust flow of refrigerant in high demand. Periods
Cap Tubes are most suited to be used on what type of equipment - answerStorage
boxes
What usually causes cap tubes to fail - answerPartial restrictions from pollutants in the
system cracks or breaks from vibration
How can you tell if a cap tube system is under charged - answerYou will have high
superheat, low sub cooling and low capacity for cooling
How can you tell if a cap tube system is overcharged - answerHigher than normal head
pressure,high sub cooling, and lower superheat resulting in possible refrigerant flooding
back to the compressor
What happens if cap tube system is under heavy load - answerTemperature recovery is
very slow since the cap Tube can only feed through a constant amount of refrigerant,
based on the minimum load that exists as the box nears it set temperature
What does a critically charged system mean - answerIt means that the system requires
an exact charge to operate efficiently and properly
Can you charge a cap tube system by head pressure alone - answerNo
Can you charge a cap tube system By superheat - answerYes but only if you wait until
the box has almost reached its operating temperature
