What is Internal and External Equalizer Expansion Valve(TXV)

Internal and external equalizers are different types of expansion valves and their working principle is similar.

We take the thermal expansion valve as an example to introduce the differences between internal and external expansion valves.

Before understanding the Internal and external equalizer thermal expansion valve, you should understand the working principle of the thermal expansion valve and the products of the thermostatic expansion valve.

There are various types of expansion valves and you can check what are the different types of expansion valves to know more about them.

Internal and external equalizer expansion valve is determined by the scope of application and environment.

Now let’s understand what is Internal and external equalizer expansion valves separately.

What are Internally Equalized Thermostatic Expansion Valves?

What are Internally Equalized Thermostatic Expansion Valves

Thermostatic Expansion Valves Brands: Danfoss, Emerson, Sporlan, Saginomiya, Sanhua, etc.

An internal equalizer expansion valve, also known as an internal equalizer TXV, doesn’t have an electronic part to adjust.

It uses fully mechanical-based adjustment by three pressure types from the feeler bulb, internal equalizer port, and spring rod pressure to balance various forces for precise control.

It is designed with internal mechanisms like a Pressure transmission unit(capillary tube), brass expansion valve seat, executive agency(ejector rod), flow control unit(valve needle), pressure sensing unit(diaphragm), etc., to equalize pressure without the need for an external line.

Check “What is a Thermostatic Expansion Valve?”

Internal equalized thermostatic expansion valves are mainly suitable for vertically mounted refrigeration and air conditioning equipment.

They are also used in low-temperature applications such as cold rooms and freezers, walk-in coolers, etc.

HUBHVACR is a manufacturer of commercial refrigeration condensing units in China.

We can offer you semi-hermetic condensing units for cold storage and cooler, walk-in cooler condensing units, cold room refrigeration units, and so on.

In addition, we can also provide you with self-contained refrigeration units, remote condensing units, drop-in refrigeration units, and Danfoss thermal expansion valves for small refrigeration equipment.

What are External Equalized Thermostatic Expansion Valves?

What are External Equalized Thermostatic Expansion Valves

An external equalizer expansion valve, or external equalizer TXV, uses an external line to connect to the suction line.

It uses the evaporator outlet pressure, connects the underside of the diaphragm, and ensures a precise superheat measurement.

In a large refrigeration system, there are more pressure drops for many reasons, such as large piping length.

An external equalizer TXV can compensate for this pressure drop and make sure there is the proper amount of refrigerant filled out in the evaporator according to the amount set in the evaporator superheat.

External equalized thermostatic expansion valves are mainly suitable for horizontally mounted refrigeration equipment and high-temperature applications such as chillers and air conditioning units.

Checking the inverter heat pump, swimming pool heat pump, and heat pump drying machine can better help you understand what an external equalizer expansion valve is.

What is the Difference Between Internal and External Equalizer Expansion Valves?

What is the Difference Between Internal and External Equalizer Expansion Valves

Internal Equalizer Expansion ValveExternal Equalizer Expansion Valve
ApplicationRefrigeration, air conditioner systemChiller, heat pump system
InstallationVerticalHorizontal
Temperature rangeLow temperatureHigh temperature
CostLowHigh
Adjustment accuracyLowHigh
Construction difficultyLowHigh
Control rangeBroadNot broad

How to Choose Internally Equalized Thermostatic Expansion Valves?

To summarize, the choice between an external equalizer TXV and an internal equalizer TXV depends on your system capacity and some other factors.

An internal equalizer TXV is mainly used in small refrigeration systems or other refrigeration systems where the pressure drop is very low.

But an external equalizer TXV is used in an HVAC system with a large pressure drop through the evaporator, more specifically, when the pressure drop exceeds 3 Psig for the air conditioning unit, 2 Psig for commercial refrigeration compressor application, and 1 Psig for other low-temperature application.

There are many considerations in selecting an expansion valve for refrigeration and air conditioning systems.

For example, the type of refrigeration compressor, heat pump compressor, and air conditioning compressor used.

Therefore, if you have questions when purchasing or designing an expansion valve, please feel free to contact us and our technical staff will provide you with a quick reply.

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