Thermostatic Expansion Valves
Thermostatic Expansion Valves
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Question 1 |
The term hunting refers to which type of metering device?
A | Low side float |
B | High side float |
C | Automatic expansion valve |
D | Thermostatic expansion valve |
Question 2 |
MOP refers to which type of metering device?
A | Low side float |
B | High side float |
C | Automatic expansion valve |
D | Thermostatic expansion valve |
Question 3 |
In a valve having a MOP (maximum operating pressure), if the pressure in the evaporator increased higher than the MOP of the valve, the valve would then tend to?
A | Open more |
B | Close until pressure is reduced |
C | Remain in equilibrium |
D | Have little effect |
Question 4 |
Liquid charge, liquid cross charge, gas charge, or gas cross charge refer to?
A | Type of charging methods |
B | Blend type refrigerants |
C | State of refrigerants in the evaporator |
D | Sensing bulb charges of the TXV |
Question 5 |
A liquid charge-sensing bulb contains?
A | A mixture of liquid and gas |
B | All gas |
C | The same refrigerant as in the system |
D | A volatile refrigerant gas mixture |
Question 6 |
A liquid cross-charge sensing bulb contains?
A | A liquid of the system’s refrigerant |
B | Gas and liquid mixtures that are the same as in the system |
C | A mixture of refrigerants that are different from that of the system |
D | A gas mixture of blend-type refrigerants |
Question 7 |
The type of sensing bulb that will prevent liquid floodback on system’s startup it the?
A | Liquid charge |
B | Liquid cross-charge |
C | Gas and gas cross-charge |
D | Gas charge |
Question 8 |
The sensing-bulb that has its own MOP is the?
A | A gas charge and gas cross-charge |
B | Liquid charge |
C | Liquid cross-charge |
D | Liquid and liquid cross-charge |
Question 9 |
To increase the superheat on a TXV one would?
A | Turn the adjusting stem counterclockwise |
B | Turn the adjusting stem clockwise |
C | Add refrigerant |
D | Recover refrigerant |
Question 10 |
To decrease the superheat on a TXV one would?
A | Turn the adjusting stem counterclockwise |
B | Turn the adjusting stem clockwise |
C | Add refrigerant |
D | Recover refrigerant |
Question 11 |
The superheat can be defined as a _________that is ________its saturation temperature for a given pressure.
A | Gas; above |
B | Liquid; above |
C | Gas; below |
D | Liquid; below |
Question 12 |
When a TXV tends to overfeed or underfeed in an attempt to find a balance point and become stable, it is known to be?
A | Drifting |
B | Hunting |
C | Balancing |
D | Stabilizing |
Question 13 |
The main function of the thermostatic expansion valve is to _________ refrigerant flow and a___________ constant superheat.
A | Control; modulate |
B | Regulate; modulate |
C | Regulate; maintain |
D | Modulate; regulate |
Question 14 |
When superheat increases at the evaporator outlet, the TXV will?
A | Close more |
B | Stabilize |
C | Balance the refrigerant |
D | Open more |
Question 15 |
The thermostatic expansion valve will decrease refrigerant flow when the superheat at the evaporator outlet
A | Rises |
B | Lowers |
C | Balances |
D | Both A and C are correct |
Question 16 |
When a thermostatic expansion valve is used, the system’s refrigerant charge is generally not as critical as it would be with?
A | An AXV |
B | An TXV |
C | A capillary tube |
D | A low side float |
Question 17 |
The sensing bulb is part of the TXV and is connected to the valve by a capillary tube to the
A | Top of the valve’s diaphragm |
B | Bottom of the valve’s diaphragm |
C | Side of the valve’s body |
D | Suction line |
Question 18 |
Pin, pin carrier, and pushrods are all components of the?
A | AXV |
B | Low-side float |
C | High-side float |
D | TXV |
Question 19 |
The component of a TXV that actually adjusts superheat is called the?
A | Superheat spring |
B | Push rods |
C | Pin carrier |
D | Diaphragm |
Question 20 |
The component of a TXV that actually adjusts superheat is called the?
A | Superheat spring |
B | Push rods |
C | Pin carrier |
D | Diaphragm |
Question 21 |
The component of a TXV that actually adjusts superheat is called the?
A | Superheat spring |
B | Push rods |
C | Pin carrier |
D | Diaphragm |
Question 22 |
Which is not an operating pressure of a thermostatic expansion valve?
A | Spring pressure |
B | Bulb pressure |
C | Condenser pressure |
D | Evaporator pressure |
Question 23 |
Which of the following pressures tends to close the TXV valve?
A | Bulb pressure/spring pressure |
B | Evaporator pressure/spring pressure |
C | Evaporator pressure/bulb pressure |
D | Bulb pressure only |
Question 24 |
The pressure that tends to open the TXV valve is the?
A | Spring pressure |
B | Evaporator pressure |
C | Evaporator and spring pressure |
D | Bulb pressure |
Question 25 |
When the system is in normal operation the sensing bulb pressure should equal the?
A | Spring pressure |
B | Evaporator pressure |
C | Spring and evaporator pressure |
D | Temperature of the entire evaporator |
Question 26 |
The function of the sensing bulb is to?
A | Sense the liquid refrigerant temperature |
B | Sense the temperature of the refrigerant vapor as it leaves the evaporator coil |
C | Sense the temperature of the entire evaporator |
D | Sense and react to high subcooling temperatures |
Question 27 |
Which pressure of the TXV will allow the valve pin to lift off the valve port?
A | Bulb pressure |
B | Spring pressure |
C | Evaporator pressure |
D | Evaporator and spring pressure |
Question 28 |
When will the TXV valve pin move to close off the valve port?
A | When bulb pressure and temperature are increased |
B | When bulb pressure increases |
C | When evaporator pressure is reduced |
D | When bulb temperature and pressure are reduced |
Question 29 |
When there is an increase in heat load on the evaporator, the refrigerant will tend to?
A | Evaporate at a slower rate |
B | Evaporate at a constant rate |
C | Evaporate at a faster rate |
D | Flood the evaporator |
Question 30 |
The term _________refers to a method of bleeding off or allowing evaporator pressure to pass through a passageway within the valve body.
A | Flooding |
B | Internally equalized |
C | Hunting |
D | Purging |
Question 31 |
The external equalizer line is connected to?
A | A hot gas bypass line |
B | A liquid line |
C | A suction line |
D | The suction header |
Question 32 |
Thermostatic expansion valves that are internally equalized should be used with?
A | Multicircuit evaporators |
B | Double-row evaporators |
C | Gravity-type evaporator |
D | Single-circuit evaporators with no more than the equivalent of 2F saturated temperature change |
Question 33 |
The equalizer line should never be?
A | Capped off soldered to the suction line |
B | Soldered to the suction line |
C | Brazed to the suction line |
D | Downstream of the sensing bulb |
Question 34 |
The external equalizer uses
A | Bulb pressure |
B | Pressure at the beginning of the evaporator |
C | Spring pressure |
D | Evaporator pressure at the evaporator outlet |
Question 35 |
The term “thermostatic charges” refers to?
A | The temperatures of the suction line |
B | The substance in the sensing bulb that responds to suction line temperatures |
C | The type of refrigerant in the system |
D | The oil and refrigerant mixture of a system |
Question 36 |
Which is not classified as a thermostatic charge?
A | Liquid charge |
B | Gas charge |
C | Liquid cross |
D | Lubricated charge |
Question 37 |
The liquid charge-sensing bulb is commonly charged with?
A | A blend-type refrigerant |
B | The same type of refrigerant that is in the system |
C | An azeotropic refrigerant |
D | A ternary mixture
|
Question 38 |
The _____________ charge TXV will always have some liquid within the bulb, capillary, and diaphragm.
A | Gas |
B | Gas cross |
C | Liquid cross |
D | Both B and C are correct |
Question 39 |
Which thermostatic charge element contains a mixture of refrigerant that will condense to a small quantity of liquid when the TXV is in its normal operating range?
A | Gas cross-charge |
B | Gas charge |
C | Liquid cross |
D | Adsorption |
Question 40 |
Which thermostatic charge element has a noncondensable gas along with a special material within the sensing bulb?
A | Gas charge |
B | Liquid charge |
C | Adsorption charge |
D | Liquid cross charge |
Question 41 |
The term “MOP” refers to?
A | More optimum pressure |
B | Maximum operating pressure |
C | Maximum optimum pressure |
D | Maximum oscillating pressure |
Question 42 |
Whenever a refrigerant distributor is used on an evaporator coil, a
A | TXV without an external equalizer should be used |
B | Nonadjustable TXV should be used |
C | TXV with an external equalizer should be used |
D | De-superheating valve should be used |
Question 43 |
The external equalizer line should be connected?
A | Downstream from the sensing bulb |
B | Upstream from the sensing bulb |
C | After an EPR valve |
D | After an accumulator |
Question 44 |
A de-superheating TXV is used in conjunction with?
A | An electric defrost system |
B | A hot gas or discharge bypass valve |
C | Gravity-type coils |
D | Ammonia-type systems only |
Question 45 |
The de-superheating TXV allows a refrigerant to?
A | Cool the warm liquid refrigerant from the condenser |
B | Allow refrigerant into the liquid line |
C | Cool the hot discharge gas that enters the suction line |
D | Subcool liquid refrigerant |
Question 46 |
Specially designed TXV’s must be used when the system’s refrigerant is?
A | R-717 |
B | R-410a |
C | R-414b |
D | R-407 |
Question 47 |
Refrigeration systems will generally operate with ________than air conditioning systems.
A | Higher superheat |
B | Lower superheat |
C | Higher subcooling |
D | Higher pressures |
Question 48 |
TXV’s can be installed?
A | Before the liquid line solenoid valve |
B | Before the filter drier |
C | At least 12” from the evaporator inlet |
D | In any position but as close to the evaporator as possible |
Question 49 |
When a refrigerant distributor cannot be directly connected to the TXV outlet, the maximum distance between the valve outlet and the distributor should not exceed?
A | 18” |
B | 24” |
C | 12” |
D | 6” |
Question 50 |
The only component that should be installed between the TXV outlet and the evaporator is?
A | Refrigerant distributor |
B | Filter drier |
C | Sight glass |
D | Solenoid valve |
Question 51 |
Static pressure will always be present in the liquid line when the TXV and the evaporator are located?
A | Below the receiver |
B | At the same level as the receiver |
C | Above the receiver |
D | Static pressure will have no influence in the performance |
Question 52 |
The contact of the TXV sensing bulb on the suction line should be direct on the piping and connected with?
A | A single bulb strap |
B | A solder connection |
C | A wrapping of cork tape |
D | Two bulb straps |
Question 53 |
The TXV sensing bulb needs to be placed at the 4 or the 8 o’clock position on the suction line when the line is?
A | 5/8” |
B | 7/8” |
C | 3/8” |
D | ¾” |
Question 54 |
The TXV sensing bulb should be installed on top of the suction line when the line is?
A | 1” OD |
B | 1¼” OD |
C | 1½” OD |
D | Smaller than 7/8” OD |
Question 55 |
When an application calls for brine tanks and water coolers to be used, the sensing bulb should be?
A | Above the liquid surface |
B | Below the liquid surface |
C | Connected to the outside of the tank |
D | Partially exposed to the ambient |
Question 56 |
Which statement is true of a TXV ?
A | It controls subcooling |
B | It keeps the evaporator flooded |
C | Some valves are of the nonadjustable type |
D | It can function as a check valve |
Question 57 |
What is the most accurate means of determining TXV performance?
A | Superheat measurements |
B | Subcooling measurements |
C | Temperature measurements |
D | Pressure-drop measurements |
Question 58 |
In general, the correct superheat will be determined on the amount of temperature difference between the?
A | Suction line temperature and the liquid line temperature |
B | Condensing temperature and the evaporator temperature |
C | Refrigerant temperature and the temperature of the suction line |
D | Suction gas temperature and the discharge gas temperature |
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