WorksheetsMetering Devices
Total questions: 20
Worksheet time: 7mins
What is the primary function of all metering devices?
To provide refrigerant to the evaporator.
To prevent liquid floodback.
To absorb heat energy.
To charge the flux capacitor.
Which devices listed are metering devices?
AEV.
Capillary tube.
PRV
Solenoid
What are two ways the metering device accomplishes its primary function?
Prevents floodback and evaporator flooding.
Changes incoming liquid to a spray and lowers its temperature.
Increases the evaporator pressure and superheat.
Increases the evaporator subcooling and decreases evaporator pressure.
Can you use a pocket thermometer to calculate superheat? Why or why not?
Yes, pocket thermometers are very accurate.
No, they are not accurate enough for measuring line temp.
What is a pocket thermometer?
Yes, because they fit nicely in the holes located in refrigerant piping.
When checking system superheat when is the best time to take reading?
When the space temperature is withing 5 degrees of design.
On initial startup of the system.
When the system is satisfied.
The third Sunday after the full moon.
Why is superheat important in a TEV system?
It keeps the temperature of the evaporator up so id doesn't freeze.
It allows the evaporator to operate at its maximum efficiency.
It acts as a margin of safety to prevent compressor damage.
It keeps the compressor lubricated.
Select the metering device from below.
Thermostatic Expansion Valve
Electronic Refrigerant Vaporizer
Refrigerant Bypass Valve
Fixed Orifice
What are the three primary forces on a TEV?
Head pressure, suction pressure and valve pressure.
Bulb pressure, evaporator pressure and spring pressure.
Bulb pressure, liquid line pressure and evaporator pressure.
Hot gas pressure, suction pressure and bulb pressure.
What is the only opening force of a TEV?
Spring pressure
Evaporator pressure
Bulb pressure
Inlet pressure
How is the factory setting of the superheat adjustment determined on a Sporlan expansion valve?
Adjust the stem all the way in until it stops.
Find the midpoint stem position.
Adjust the stem all the way out until it stops.
Adjust the refrigerant charge.
What are the three criteria needed for a TEV to work correctly?
Valve sized correctly, bulb installed correctly and complete liquid to the valve.
Valve sized correctly, bulb tight to the pipe and high pressure to the valve.
Valve sized correctly, bulb mounted on pipe bottom and pressure to the valve.
Valve sized correctly, bulb mounted to the pipe and complete liquid to the valve.
According to valve manufacturers, where should the TEV sensing bulb be mounted on a horizontal suction line that is 7/8" in diameter or larger?
Ont the top of the suction line.
On the bottom of the suction line.
At the 4 or 8 o'clock position.
At the 4 to 8 o'clock position.
What happens to the capacity of a TEV as the liquid temperature decreases?
The capacity decreases due to less refrigerant flow.
The capacity increases due to less adiabatic expansion.
The capacity decreases due to less adiabatic expansion.
The capacity increases due to more refrigerant flow.
How do you know if a TEV is flooding?
Low superheat.
High superheat.
No superheat.
High subcooling.
How do you know if a TEV is starving
Low superheat.
High superheat.
Low subcooling.
High subcooling.
How do you know if a TEV is hunting?
Low superheat.
High superheat.
Superheat fluctuates.
No superheat.
What is a pressure transducer?
A safety control to prevent low pressure.
A pressure sensing device that sends information to the controller.
A pressure sensing device to monitor pressure.
A safety control to prevent low temperature.
What are the main reasons for using an expensive EEV over a standard TEV?
Customer wants units with better technology.
EEV's are more profitable.
Better system efficiency and control.
It has electrolytes.
What is a thermistor?
A safety control to prevent low temperature.
A safety control to prevent high pressure.
A device that changes temperature to pressure.
A device that changes resistance in response to temperature changes.
What is the benefit of preventing a system's pressures from equalizing during the off cycle?
The evaporator is less likely to flood the compressor.
The compressor will draw less starting current.
The system reaches its rated capacity sooner after startup.
The condenser creates superheated refrigerant quicker.
