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
Spring pressure and _____ pressure are part of the automatic expansion valve. A Evaporator B Bulb C Condenser D Compressor
A Evaporator
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 can adjust the refrigerant flow rate to compensate for varying loads. A True B False
A True
A TXV will stay closed until the sensing bulb pressure overcomes the low side pressures and spring pressure. ATrue B False
A True
A filter drier should be placed in the liquid line ahead of the TXV. A True B False
A True
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
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
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
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.
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
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
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
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
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 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
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
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
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
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
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
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