hvac metering devices
A(n)_________valve is an electromagnet with a movable core that opens and closes a fluid passage. A Solenoid B Bypass C Check D Defrost
A Solenoid
This is a pressure controlled valve without a sensing bulb. A TXV B AXV C EEV D Bleed valve
B AXV
A TXV can adjust the refrigerant flow rate to compensate for varying loads. A True B False
A True
A filter drier should be placed in the liquid line ahead of the TXV. A True B False
A True
Where on the refrigeration system would you clamp the TXV's bulb? A To the liquid line after the condenser. B To suction line after the evaporator. C To the discharge line before the condenser. D To the liquid line before the evaporator.
B To suction line after the evaporator
When an external equalized TXV is used where should the equalized line be connected? A Before the evaporator. B To the suction line down flow from the TXV bulb. C To the discharge line before the condenser. D To the suction line before the TXV bulb.
B To the suction line down flow from the TXV bulb.
Since the direction of an EEV's travel is based on the direction of the stepper motor and lead screw, the stepper motor can: A Modulate the valves position B Close the valve C Open the valve D All of the above
D All of the above
A liquid cross-charge sensing bulb may use a mixture of different refrigerants to achieve the desired operating characteristics. A True B False
A True
An automatic expansion valve does not have a sensing bulb. A True B False
A True
The amount of evaporator surface required for superheating depends on the temperature difference between the media being cooled and: A The amount of sub-cooling B The refrigerant temperature C The temperature of the saturated liquid D The head pressure of the system
B The refrigerant temperature
The amount of evaporator surface required for superheat depends on the temperature difference between the media being cooled and____________ A The amount of sub-cooling B The refrigerant temperature C The temperature of the saturated liquid D The head pressure of the system
B The refrigerate temperature
This valve uses an electric operator instead of a diaphragm power assembly. A TXV B AXV C EEV D Solenoid valve
C EEV
Which one below is NOT one of the three basis on which the nominal capacity ratings are established for refrigerants using TXV's? A Pressure drop across the port B Evaporator temperature C Evaporator pressure D Liquid sub-cooling
C Evaporator pressure
To help prevent contaminants form entering the capillary tube a(n)_______is usually installed between the liquid line or condenser and the capillary tube. A Evaporator B Condenser C Filter drier D Modulator
C Filter drier
Which one below is NOT a part of the TXV? A The push rods B The seat C The piston D The pin
C The piston
The thermostatic expansion valve is operated by a pressure difference between the sensing bulb pressure and the _____ pressure. A Liquid line pressure B Spring pressure C Compressor pressure D None of the above
D None of the above
Spring pressure and _____ pressure are part of the automatic expansion valve. A Evaporator B Bulb C Condenser D Compressor
A Evaporator
To increase the superheated setting on the TXV in which direction would you adjust the stem? A Up B Down C Clockwise D Counter clockwise
C Clockwise
What is the basic function of the TXV's? A Control the temperature of the living space B Control the suction pressure C Control the superheat D Control the humidity
C Control the superheat
Most HVACR systems use a standard TXV with a _______: A Sensing bulb B Single inlet C Single outlet D All of the above
D All of the above
When a capillary tube has a larger diameter the length of the capillary tube must be ______ to have the same effect as one with a smaller diameter. A Longer B Shorter C Of equal length D None of the above
A Longer
The thermostatic expansion valve is operated by a pressure difference between the sensing bulb pressure and the ________ pressure A Low side B High side C Liquid line D None of the above
A Low side
Which one below is NOT one of the eight essential parts of the TXV? A Piston B The seat C The push rod D The spring guide
A Piston
The ________ inside a sensing bulb changes with the temperature at the evaporator outlet. A Pressure of the refrigerant B Quantity of refrigerant C Weight of the refrigerant D None of the above
A Pressure of the refrigerant
When there is liquid in the process of vaporizing or boiling into a vapor we call this process: A Saturated liquid B Saturated vapor C Latent heat of fusion D Latent heat of condensation
A Saturated liquid
What is the name of the heat that add's superheat to the refrigerant? A Sensible heat B Latent heat of condensation C Total heat D Latent heat of vaporization
A Sensible heat
Which TXV pressure once set is constant? A Spring pressure B Bulb pressure C Evaporator pressure D Condenser pressure
A Spring pressure
Although the EEV is electronically driven and is electronically controlled, it performs the same function as a thermostatic expansion valve restricting ____ to a desired setting. A Superheat B Sub-cooling C Flash gas D Spring pressure
A Superheat
Increasing the _______ too much will starve the evaporator. A Superheat B Sub-cooling C Pressure D None of the above
A Superheat
The temperature difference between the refrigerant temperature in the sensing bulb and the temperature in the evaporator is often described as the operating ______ of the valve. A Superheat B Sub-cooling C Flooding gas D Flash gas
A Superheat
If the thermal bulb on a TXV comes loose from the mounting at the outlet of the evaporator, which of the following will occur? A The valve will open, feeding more refrigerant to the evaporator. B The valve position will remain unchanged, and the pressure in the bulb will remain the same. C The valve will close, starving the evaporator D The suction pressure will drop
A The valve will open, feeding more refrigerant to the evaporator.
A TXV will stay closed until the sensing bulb pressure overcomes the low side pressures and spring pressure. ATrue B False
A True
Four-way solenoid valves are used chiefly on heat pumps to switch between heating and cooling modes as needed. A True B False
A True
Hunting may allow liquid refrigerant to reach the compressor and cause compressor damage. A True B False
A True
If the orifice of a valve assembly is oversized, the valve will hunt or surge. A True B False
A True
In a PWM solenoid EEV, a control signal rapidly opens and closes a solenoid valve at different speeds in order to vary refrigerant flow. A True B False
A True
In a PWM solenoid EEV, a control signal rapidly opens and closes a solenoid valve at different speeds in order to vary refrigerant flow. A Tue B False
A True
The diagram of an automatic expansion valve separates the atmospheric pressure and the system pressure. A True B False
A True
The higher the temperature in a low side float (LSF) system the higher the low side pressure. A True B False
A True
The longer the capillary tube the greater the pressure drop. A True B False
A True
The type of sensing bulb charge used in a TXV affects how it reaches to conditions within a system. A True B False
A True
Unless an automatic expansion valve is equipped with a bleeder or bypass, the high side and low side pressures will not balance during the off cycle. A True B False
A True
The valve is used to block refrigerant flow through a single circuit on demand. A Two way valve B Three way valve C Four way valve D Check valve
A Two way valve
Which component is NOT a type of metering device? A Capillary tube B Bare tube C Automatic expansion valve D Thermostatic expansion valve
B Bare tube
Some thermostatic expansion valves are equipped with built-in ______ to prevent refrigerant from flowing back through the TXV. A Bleed valve B Check valve C Solenoid valve D Piston valve
B Check valve
When the capillary tube serves the function of both the liquid line and the metering device it is connected between the evaporator and the: A Suction Line B Condenser C Compressor D Modulator
B Condenser
The thermostatic expansion valve reduces the flow rate as the evaporator _______: A Warms B Cools C Runs D None of the above
B Cools
The smaller the diameter of the capillary tube, the smaller the pressure drop. A True B False
B False
Refrigerant enters the metering device as a: A Low-pressure liquid B High-pressure liquid C Low-pressure vapor D High-pressure vapor
B High-pressure liquid
Refrigerant enters the metering device as a___________> A Low-pressure liquid B High-pressure liquid C Low-pressure vapor D High-pressure vapor
B High-pressure liquid
If the TXV is adjusted correctly, it will close and remain closed whenever the compressor is__________. A Running B Idle C Cold D All of the Above
B Idle
In what way can a TXV equalize? A By shutting the system down B Internally C Externally D All of the above
B Internally & C)Externally
The capacity of a given expansion valve is determined by what two basic components? A Net Refrigeration Effect and Sub-cooling B Mass Flow Rate and Net Refrigeration Effect C Mass Flow Rate and Superheat D Superheat and Sub-cooling
B Mass Flow Rate and Superheat
The capacity of a given expansion valve is determined by what two basic components? A Net Refrigeration Effect and sub-cooling B Mass flow rate and Net Refrigeration Effect C Mass flow rate and superheat D Superheat and sub-cooling
B Mass flow rate and Net Refrigeration Effect
The amount of heat required to evaporate one pound of a given refrigerant is called? A NRA B NRE C NFL D NBA
B NRE
Capillary tubes may become plugged due to wax build up from _______ in the system. A Expansion within the system B Overheating of the oil C Overcharging of the system D None of the above
B Overheating of the oil
When used with thermostatic expansion valves, the term superheat refers to the difference in temperature between the evaporator inlet and the_____. A Liquid line B Sensing bulb C Fitting D Spring
B Sensing bulb
What is the name of the metering device that consist of a length of seamless tubing with a small and precisely formed inside diameter? A Automatic expansion tube B Thermal expansion tube C Capillary tube D Electronic expansion tube
C Capillary tube
Extra refrigerant in a system using a capillary tube will increase the risk that liquid refrigerant could be drawn in to the________. A Capillary tube B Filter drier C Compressor D Evaporator
C Compressor
Which condition below is NOT one that would happen in a system with a restricted capillary tube? A Suction pressure would drop B Discharge pressure would increase C Flood back to the compressor D Less refrigerant would flow into the evaporator
C Flood back to the compressor
To maintain a constant pressure in the evaporator when the system is running, an AXV_________ the refrigerant flow when the evaporator pressure drops. A Decreases B Stabilizes C Increases D None of the above
C Increases
To maintain a constant pressure in the evaporator, when the system is running, an AXV _____ refrigerant flow when the evaporator pressure drops. A Decreases B Stabilizes C Increases D None of the above
C Increases
A low superheat setting can lead to: A Compressor over heating B Evaporator coil icing C Liquid flood back D High discharge pressure
C Liquid flood back
This TXV bulb is charged with the same refrigerant used in the system, some of which remains liquid under all operating conditions. A Liquid cross- charged B Adsorption liquid charge C Liquid-charged D Gas-charged
C Liquid-charged
Controllers on EEV systems usually include the pressure temperature tables for a number of _____ to allow the user to select the correct one for the application. A Devices B Motors C Refrigerants D Temperatures
C Refrigerants
Controllers on EEV systems usually include the pressure-temperature tables for a number of_____ to allow the user to select the correct one for the application. A Devices B Motors C Refrigerants D Temperatures
C Refrigerants
Pulse width modulating (PWM) solenoid EEV's are refrigerant metering devices that use a pulse width modulation signal to control the operation of a ____ for variable refrigerant flow. A Check valve B Sensing Bulb C Solenoid valve D Bleed valve
C Solenoid valve
This valve uses a plunger to open and close a fluid passage. A Four way valve B Thermostatic expansion valve C Solenoid valve D Bleed valve
C Solenoid valve
During the off cycle, as the sensing bulb pressure and the low side pressure cancel each other out, the ________ pressure is enough to force the TXV firmly into its seat and stop refrigerant flow. A Line B High side C Spring D Pump
C Spring
The TXV maintains a fully fed evaporator by controlling the: A Evaporator pressure B Condenser pressure C Superheat D Liquid sub-cooling
C Superheat
A change in the sensing bulb ______ will cause a corresponding change in the sensing bulb pressure. A Refrigerant B Microns C Temperature D Charge
C Temperature
Solenoid valves A Open refrigerant circuit B Are activated by a thermostat C Close refrigerant circuits D All of the above
D All of the above
Solenoid valves_____ A Open refrigerant circuits B Are activated by a thermostat C Close refrigerant circuits D all of the above
D All of the above
The ______ of the capillary tube determines how much the pressure drops between the condenser and the evaporator. A Length B Inside diameter C Number of turns D All of the above
D All of the above
The vapor that is produced by the pressure drop by a capillary tube is known as_______. A Superheat B Sub-cooling C Flooding gas D Flash gas
D Flash gas
What is the name given to the refrigerant that forms in the evaporator due to a sudden drop in pressure between the high side and the low side of the system? A Flooding B Gas cross charged C Sub-cooling D Flash gas
D Flash gas
What is the heat called that represents nearly all the heat transfer that takes place in the evaporator? A Sensible heat B Latent heat of condensation C Total heat D Latent heat of vaporization
D Latent heat of vaporization
The piping between the condenser and the metering device is called? A Suction line B Discharge line C Expansion line D Liquid line
D Liquid line
This valve is able to change its orifice size to account for changes in cooling loads. A Bleed valve B Automatic expansion valve C Electronic expansion valve D Modulating valve
D Modulating valve
Where on the suction line should you never place the TXV sensing bulb? A On the tope of the suction line B On the right side of the suction line C One the left side of the suction line D On the bottom of the suction line
D On the bottom of the suction line
The amount of temperature increase above the saturation point is called: A Sensible temperature B Latent temperature C Sub-cooling temperature D Superheat temperature
D Superheat temperature
