NATE: TEV, TXV

Created by roliman 

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The term hunting refers to which type of metering device:

thermostatic expansion valve

MOP refers to which type of metering device:

thermostatic expansion valve

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:

close until pressure is reduced

Liquid charge, liquid cross-charge, gas charge, or gas cross-charge refer to:

sensing bulb charges of a TXV

A liquid charge-sensing bulb contains:

the same refrigerant as in the system

A liquid cross-charge-sensing bulb contains:

a mixture of refrigerants that are different from that of the system

The type of sensing bulb that will prevent liquid floodback on system's startup is the:

gas and gas cross-charge

The sensing-bulb type that has its own MOP is the:

gas charge and gas cross-charge

To increase the superheat on a TXV one would:

turn the adjusting stem clockwise

To decrease the superheat on a TXV one would:

turn the adjusting stem counterclockwise

The superheat can be defined as a ____ that is ____its saturation temperature for a given pressure.

gas; above

When a TXV tends to overfeed or underfeed in an attempt to find a balance point and become stable, it is known to be:

hunting

The main function of the thermostatic expansion valve is to ____ refrigerant flow and ____ a constant superheat.

regulate: maintain

When superheat increases at the evaporator outlet, the TXV will:

open more

The thermostatic expansion valve will decrease refrigerant flow when the superheat at the evaporator outlet:

lowers

When a thermostatic expansion valve is used, the system's refrigerant charge is generally not as critical as it would be with:

a capillary tube

The sensing bulb is part of the TXV and is connected to the valve by a capillary tube to the:

top of the valve's diaphragm

Pin, pin carrier, and pushrods are all components of the:

TXV

The component of a TXV that actually adjusts superheat is called the:

superheat spring

Which is not an operating pressure of a thermostatic expansion valve:

condenser pressure

Which of the following pressures tends to close the TXV valve:

evaporator pressure/spring pressure

The pressure that tends to open the TXV valve is the:

bulb pressure

When the system is in normal operation the sensing-bulb pressure should equal the:

spring and evaporator pressure

The function of the sensing bulb is to:

sense the temperature of the refrigerant vapor as it leaves the evaporator coil

Which pressure of the TXV will allow the valve pin to lift off the valve port:

bulb pressure

When will the TXV valve pin move to close off the valve port:

when bulb temperature and pressure are reduced

When there is an increase in heat load on the evaporator, the refrigerant will tend to:

evaporate at a faster rate

The term ____ refers to a method of bleeding off or allowing evaporator pressure to pass through a passageway within the valve body.

internally equalized

The external equalizer line is connected to:

a suction line

Thermostatic expansion valves that are internally equalized should be used with:

single-circuit evaporators with no more than the equivalent of 2° F saturated temperature change

The equalizer line should never be:

capped off

The external equalizer uses:

evaporator pressure at the evaporator outlet

The term thermostatic charges refers to:

the substance in the sensing bulb that responds to suction line temperature

Which is not classified as a thermostatic charge:

lubricated charge

The liquid charge-sensing and gas charge-sensing bulb is commonly charged with:

the same type of refrigerant that is in the system

The ____ charge TXV will always have some liquid within the bulb, capillary, and diaphragm.

liquid cross-

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:

gas cross-charge

Which thermostatic charge element has a noncondensable gas along with a special material within the sensing bulb:

adsorption charge

The term "MOP" refers to:

maximum operating pressure

Whenever a refrigerant distributor is used on an evaporator coil, a:

TXV with an external equalizer should be used

The external equalizer line should be connected:

downstream from the sensing bulb

A de-superheating TXV is used in conjunction with:

a hot gas or discharge bypass valve

The de-superheating TXV allows refrigerant to:

cool the hot discharge gas that enters the suction line

Specially designed thermostatic expansion valves must be used when the system's refrigerant is:

R-717

Refrigeration systems will generally operate with ____ than air conditioning systems.

a lower superheat

Thermostatic expansion valves can be installed:

in any position but as close to the evaporator as possible

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:

24"

The only component that should be installed between the TXV outlet and the evaporator is the:

refrigerant distributor

Static pressure will always be present in the liquid line when the TXV and the evaporator are located:

above the receiver

The contact of the TXV sensing bulb on the suction line should be direct on the piping and connected with:

two bulb straps

The TXV sensing bulb needs to be placed at the 4 o' clock or the 8 o' clock position on the suction line when the line is:

7/8" OD or larger

The TXV sensing bulb should be installed on top of the suction line when the line is:

smaller than 7/8" OD

When an application calls for brine tanks and water coolers to be used, the sensing bulb should be:

below the liquid surface

Which statement is true of a thermostatic expansion valve:

Some valves are of the nonadjustable type

What is the most accurate means of determining TXV performance:

superheat measurements

In general, the correct superheat will be determined on the amount of temperature difference between the:

refrigerant temperature and the temperature of the suction line

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