Expansion Valve
Expansion Valve

Miracle cooperated with an expansion valve factory that has more than 60 years’ experience in R&D, manufacturing,

and marketing expansion valves.

Expansion Valve Supplier Video Cover

Your Best Expansion Valve Supplier

Your best expansion valve supplier with 60 years of profession;

Internal equalizer and external equalizer with the different cooling capacity orifice to meet your request;

Miracle expansion valve suitable for a variety of refrigerants to meet the needs of the household and commercial units.

Miracle’s expansion valves now cooperated with many famous brands, such as Carrier, York, Trane, Midea, Gree, Mcquay, Tica brands.

Thermostatic Expansion Valve

The thermostatic expansion valve is a new generation of expansion valves with a replaceable orifice. It is a very important refrigeration part for the refrigeration system and AC system, suitable for automatic supply and adjustment for small and medium-size evaporators. The thermostatic expansion valve is installed between the liquid receiver and evaporator, to turn the high pressure and high-temperature liquid refrigerant to low-pressure wet steam by expansion valve throttling, and the low-pressure wet steam will absorb the heat when evaporating so that it will achieve the cooling function.

Thermostatic Expansion Valve Orifice

The thermostatic expansion valve orifice is used for the above type replaceable thermostatic expansion valve. Please kindly check the following technical data to choose the suitable model orifice for your expansion valve by choosing the right refrigerating capacity. We have 7 models orifices from No.1 to No.6, which is quite similar to Emerson and Danfoss, check their original code to choose our model quickly. If you don’t know how to choose, please contact us for a professional suggestion.

R410 Thermostatic Expansion Valve

R410 Thermostatic expansion valve is a type of integrated expansion valve, different from the above replaceable orifice expansion valve, this type can’t replace the orifice. It is specially designed for the R410 refrigerant system, widely used for air conditioning, commercial refrigeration, transportation refrigeration, and freezing fields.

Electronic Expansion Valve

DPF series Electric expansion valve is mainly used for commercial refrigeration, air conditioning, and heat pump systems. It can achieve the function of automatically adjusting the refrigerant flow, making sure the refrigeration system can run under perfect working conditions, then to fulfill the cooling or heating in a rapid way. With this electric expansion valve, it can control the temperature very accurately, also will save energy for you.

Why Miracle

The refrigeration expansion valve factory is founded in 1951, for now, it has 69 years of experience in R&D, manufacturing, and marketing expansion valves.

In the Year 1985, it cooperated with Alco company to design new type expansion valves.

Now our customers include Carrier, York, Trane, Midea, Gree, Mcquay, Tica, etc famous brands, quite popular in China and overseas markets.

To better develop the overseas market, now we have CE, UL, CQC certifications.

Miracle provides different types of thermostatic expansion valves and electronic expansion valves. Miracle expansion valve has CE and UL certificates.

Welcome to visit our expansion valve factory

Here we collected some common failures situations from our own using and our customers’ using, they are all small faults, you can deal with them by yourself without panic, and protect the expansion valve and refrigeration system.

At the same time, increase your skills for dealing with expansion valves to fulfill their perfect performance. If there is any analysis that is not clear for you, please contact us for further explanation.

Common failure and treatment methods of Expansion Valve
Common failure and treatment methods of Expansion Valve

Design is the beginning of quality, quality is the guarantee of success! Miracle always insists on doing things with heart.

What is Refrigeration Expansion Valve?

What is Refrigeration Expansion Valve

The refrigeration expansion valve, also called the thermostatic expansion valve, is one of the 4 major parts of the refrigeration system(the rest are compressor, evaporator, and condenser).

The expansion valve now is widely used for the Freon and Ammonia refrigeration system, as the throttling mechanism.

It can automatically adjust the refrigerant flow to enter into the evaporator according to two factors, one is the temperature of the refrigerant that flows out from the evaporator, the other is the pressure signal.

So the thermostatic expansion valve is a flow adjustment mechanism, it is composed of a signal collector, a signal sender, and a flow regulator.

The expansion valve has an internal balance and external balance.

What’s Their Difference?

What’s Their Difference

Internal balance is a pressure balancing method by transferring the outlet pressure of expansion valve to the power actuator through the internal channel;

External balance is a pressure balance method by transferring the outlet pressure of the expansion valve to the actuator of the valve through the external channel.

It uses for compensating the pressure drop effect of refrigerant flowing through the distributor and evaporator.

Miracle provides the expansion valve for R134A, R22, R404, R502, R507, and R410 refrigerants to fulfill your different applications.

Except for the thermostatic expansion valve, we also have an electric expansion valve to meet your demands.

Thermostatic Expansion Valve Features:

Thermostatic Expansion Valve Features

It has a reliable superheat regulation function, it will make sure good heat exchange for evaporator during the low temperature.

Internal and External are all available for you.

Replaceable orifice will be easier for adjustment to match the condensing unit and refrigeration system, also it’s very easy for maintenance.

Suitable for R134A, R22, R404, R502, R507 refrigerants.

Safety working pressure is 3MPA.

Overheat adjustment function.

If you use Emerson or Danfoss expansion valve, we provide the original code for you to choose the replaceable expansion valve for yourself.

R410 Thermostatic Expansion Valve Features:

R410 Thermostatic Expansion Valve Features

Specially use for R410 refrigerants.

Max’s working pressure is 45BAR.

The evaporation temperature range is from -40℃ to +15℃.

It provides the MOP function, it can protect the max pressure to 170psi.

The overheat adjustment range is from 1k to 8k.

It also has an internal and external balance for your reference.

Electronic Expansion Valve Features:

Electronic Expansion Valve Features

Suitable for R22,R134A,R404A,R407C,R507C and R410A refrigerants.

Low noise and energy saving.

Suitable for AC, heat pump, and refrigeration system.

Applicable for ambient temperature from -30℃ to +60℃.

Max working pressure is 4.5MPA.

Expansion Valve Work Principle

Expansion Valve Work Principle

Miracle as a trusted refrigeration valve manufacturers and supplier design the refrigeration expansion valve.

So that we manage the flow of the refrigerant into the evaporator and maximize its efficiency.

This expansion valve is generally located close to the inlet of the evaporators.

Some main components of refrigeration expansion valves are a sensing bulb filled by refrigerant located in the outlet of an evaporator and connected with a powerhead.

There is a diaphragm that separates the pressure.

After that, there is also an adjustable pressure string on the bottom of the diaphragm.

The stem rotates clockwise to decrease and counterclockwise to increase the pressure of this spring.

The condensed high-pressure saturated liquid refrigerant enters the expansion valve, passes through the throttling of the valve port, and flows out from the expansion valve outlet.

So how does the evaporator valve control the refrigerant entering into the evaporator?

Once the pressure in the top of the powerhead reaches a certain point, the diaphragm is pushed down.

So the expansion valve opens wides, and more liquid refrigerant enters into the evaporator.

Absorb the heat from the surrounding environment to achieve cooling.

In the same way, when the pressure above the diaphragm, the powerhead decreases to a certain point, the valve retracts the refrigerant flow is reduced.

What’s the Thermal Expansion Valve Used For?

What’s the Thermal Expansion Valve Used For

The main function of the expansion valve is to adjust the high and low pressure in the system, and it is a component for gas and liquid conversion.

Miracle expansion valves can be used in the following systems:

Refrigeration System

Air Conditioner System

HVAC System

Analysis of Balance Force of Thermal Expansion Valve

The internal balance expansion valve has a channel in the valve,  to transfer the evaporation pressure P2 at the export of the thermal expansion valve to the diaphragm’s lower cavity and produce a balancing force.

Internal Balance Thermal Expansion Valve
Internal Balance Thermal Expansion Valve

In the externally balanced thermal expansion valve system, the external balance thermal expansion valve transmits the evaporator’s outlet pressure P3, to the lower cavity of the powerhead through the external balance pipe to generate a balance force F2.

External Balance Thermal Expansion Valve
External Balance Thermal Expansion Valve

Force analysis of valve needle displacement when thermal expansion valve automatically adjusts the flow

Thrust balanced formula


When F1>F2+F3-F4+F5, the superheat will increase, the valve needle will move down, and the valve opening will increase the flow rate.

When F1>F2+F3-F4+F5, the superheat will decrease, and the valve needle will move upward, then close the valve, on this ground, the liquid flow will decrease.

The internal balance expansion valve has a channel to transfer the evaporation Ejection force P2 at the thermal expansion valve export to the lower cavity of the expansion valve diaphragm to generate a balancing force.

In the Thrust Balance Formula:

In the Thrust Balance Formula

F1—The upper diaphragm cavity in the powerhead and the temperature sensor have the ejection force between them, and this pressure will cause a thrust.

F2—The evaporating pressure from the expansion valve P2 part will produce a force in the lower cavity of the diaphragm.

The force generated by the external balance expansion valve to the balance pipe to transfer the evaporation pressure of the P3 evaporator outlet to the lower cavity of the diaphragm

F3—The lower part of the valve needle adjusts the preload of the spring.

F4—The thrust generated by the evaporation pressure P2 on the valve needle.

F5—The thrust produced by the inlet pressure P1 on the valve needle.

P1—The pressure when the refrigerant enters the valve port (high pressure)

P2—Evaporating pressure at valve outlet (low pressure)

P3—The evaporator outlet, which is the external pipe produces the evaporation pressure (low pressure)

S—cross-sectional area of the valve port



The two thrusts of F4 and F5 are negligible in systems with relatively small cooling capacity, small load changes in the system of the expansion valve, relatively stable systems.

But the expansion valve with a large cooling capacity (large valve port cross-sectional area) has a large load change and unstable operation For the system, F4 F5 affects the opening superheat of the valve.

Installation of the Expansion Valve

Installation of expansion valve

Install the expansion valve temperature sensor at the outlet of the evaporator.

It is necessary to connect the balance pipe to the intake pipe and make sure the position is near the expansion valve bulb’s back end.

Install the expansion valve body to the liquid pipeline where is the entrance of the evaporator.

Expansion Valve Installation Tips?

Expansion Valve Installation Tips

The thermal expansion valve has two types: internal type and external type expansion valve according to the pressure balance structure.

Please pay attention to the following points for how to install an expansion valve:

Pay attention to the flow direction.

Install the expansion valve body vertically.

The temperature sensing bag should be placed horizontally or head down, and be wrapped with heat-insulating material.

The interface of the outer tube at the outlet of the evaporator should be close to the temperature sensing ball.

When welding the interface, use wet cotton yarn to wrap the expansion valve up to avoid overheating or low temperature, etc., and adjust the evaporation temperature after everything is installed.

Expansion Valve Temperature Sensing Package Installation Tips

Expansion Valve Temperature Sensing Package Installation Tips

Make sure to install the expansion valve’s temperature sensing bulb on the horizontal pipe.

If the actual situation s is not allowed to do that, then it has to ensure the capillary tube is toward up

If a vertical pipeline and the capillary point downwards, it may cause the refrigerant to migrate to the thermostatic element, which will cause the expansion valve to malfunction.

When you confirm the expansion valve bulb installation position, you should refer to the suction pipe diameter, which is very important;

It is not correct to install the expansion valve temperature sensor on the end of the evaporator pipe, or you will get a false signal from the compressor oil return.

Make sure to install the expansion valve temperature sensor not be close to large components;

The installation position of the expansion valve temperature sensing bulb cannot be at the back end of the heat exchanger;

Do not install the expansion valve temperature sensor in a place where the outside heat/cold area is in contact;

If there is heating flow in the environment of the expansion valve bulb, then it’s better to do the heat insulation treatment on the bulb;

The expansion valve temperature sensor should be installed on the horizontal pipeline.

Expansion Valve Temperature Sensor Installation Steps

Expansion Valve Temperature Sensor Installation Steps

The Steps to install the temperature sensor with lashing tape.

Step 1: Pass the lashing tape through the notch.

Step 2: Put the expansion valve bulb between the lashing tape and the capillary tube, and tighten the lashing tape.

Step 3: When the correct bend mark enters the groove, bend the tie so that the bolt can pass.

Step 4: Tighten the bolts and fix the expansion valve bulb.

Step 5: Wrap the excess lashing tape.

Principle and Debugging of Expansion Valve Superheat

Superheat Setting:

Expansion Valve Superheat Setting

For getting the best system performance, you should adjust the expansion valves superheat;

The method to lower the superheat is to rotate the rotary rod counterclockwise step by step until the fluctuation is observed;

The difference of ±0.5℃ is not regarded as fluctuation;

Superheat Measurement:

Expansion Valve Superheat Measurement

The superheat degree should refer to the heat degree which is increased on the saturated suction temperature;

Superheat degree=(the suction temperature)-(the saturation temperature caused by the suction pressure);

The thermal expansion valves superheat cannot be less than 6-8℃;

Mostly, you can measure the back end temperature of the distributor by estimating the evaporation temperature, because the distributor end temperature is the same as the wet suction temperature;

Debugging of Overheating:

Expansion Valve Debugging of Overheating

Overheating is too high

Possible cause: the valve opening is too small;

Overheating is too low

Possible cause: the valve opening is too large;

Connect the Expansion Valve to the Distributor

You should make sure the bent straight pipe’s length is more than 7 times the pipe diameter, otherwise, uneven liquid dispensing will be caused.

Expansion Valve Connected to The Distributor

Once the system uses a liquid distributor, an externally balanced thermal expansion valve must be used;

The pipe diameter and length of all distributors must be the same.

Otherwise, it is easy to cause uneven liquid distribution.

Precautions for connection of expansion valve and distributor

Connection Method of Expansion Valve and Evaporator

If the two evaporators are arranged up and down.

You must equip an oil trap with the suction pipe to avoid the liquid or compressor refrigerating oil to flow into the lower evaporator;

How to Check the Refrigerant Loss for the Expansion Valve?

How to Check the Refrigerant Loss for the Expansion Valve

For valves with replaceable orifices, the refrigerant loss of the power unit is easy to check.

Close the orifice or the orifice assembly to the diaphragm and check the orifice spring’s elasticity.

If the spring is not elastic, the refrigerant is gone.

The elasticity indicates that there is still refrigerant in the power element.

For more refrigerant leak inspection methods, please check how to detect refrigerant gas leaks.

The Thermal Expansion Valve Can Not Inject Refrigerant?

The Thermal Expansion Valve Can Not Inject Refrigerant

If you install a solenoid valve upstream of the expansion valve, the first step is to open the solenoid valve.

Then you can easily check the valve to see if there are symptoms of overheating, such as discoloration.

Check the capillary to see if it is broken or squeezed.

Check the thermal expansion valve to avoid all the debris being filtered by the filter drier.

If the thermal expansion valve still cannot inject refrigerant, please replace the expansion valve.

The Expansion Valve Intake Pipe is Overheated?

The Expansion Valve Intake Pipe is Overheated

Check whether the system’s subcooling degree is correct. If the subcooling degree is too low.

Then there is the possibility that the expansion valve’s inlet exists the flash gas, and refrigerant needs to be added.

Check the interface size according to the cooling system’s capacity.

Please select and replace with the correct size when the size is not matched.

Check whether the liquid line is blocked, such as blocked line components, or valves that can only be partially opened

Try to adjust the superheat in a counterclockwise direction and observe whether the valve responds.

The Thermal Expansion Valve Can Not Adjust the Superheat?

The Thermal Expansion Valve Can Not Adjust the Superheat

Ensure that the expansion valve temperature sensor and the suction pipe have a good condition, which ensures the sensor has good heat insulation.

When adjusting the superheat, please rotate about a full circle, and then wait five minutes for the input to take effect.

If the valve is unstable, increase the superheat slowly until the valve stops vibrating.

There is Liquid at the Outlet of the Evaporator?

There is Liquid at the Outlet of the Evaporator

This kind of phenomenon is mainly caused by improper adjustment of the system overheating, expansion valve bulb position, and heat insulation.

Check whether the evaporator airflow is proper, whether there are ice and dirt on the evaporator.

Slowly adjust the superheat in a clockwise direction until there is enough superheat.

Incorrect Overheating?

Incorrect Expansion Valve Overheating

Adjust the overheating degree after you confirm you have a stable refrigeration system and the load is not high.

Please be noted that, if you open the expansion valve under high load conditions, such as emptying the system or completing the defrost.

Then it is a normal situation that overheating or higher evaporation pressure or higher temperature.

Can the Expansion Valve be Installed Upside Down?

Can the Expansion Valve be Installed Upside Down

The answer is no. Please make sure to install the thermal expansion valve near the evaporator, and not tilt or install it upside down.

Since when the thermal expansion valve work, it has to rely on the temperature sensed according to the temperature sensing bulb.

If the temperature sensing system’s sensitivity is low, the time lag of the transmission signal is large.

It will be easy to cause and fluctuations in the liquid supply. So, the installation is very important.

How Does the Expansion Valve Opening Degree Affect the Superheat Degree?

How Does the Expansion Valve Opening Degree Affect the Superheat Degree

The expansion valve opening degree in the cold storage refrigeration system has a great relationship with the superheat degree.

When the superheat is large, the opening degree is also large; when the degree of superheat is small, the opening degree is also small.

When the degree of superheat decreases to a certain value, the expansion valve just closes at the moment, which is the degree of superheat at which the expansion valve opens.

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