How to Choose Right Expansion Valve for Your HVAC&R System?

Before learning how to choose the right expansion valve you should understand what is superheating and subcooling, what is refrigeration system, and how expansion valves work.

If you are already familiar with these, continue reading the rest of this article.

After getting all of this knowledge about expansion valves, you know that in HVAC&&R systems, expansion valves are categorized as thermal expansion valves, electronic expansion valves, and capillary expansion valves.

Each type of expansion valve corresponds to a different type of refrigeration equipment and compressor.

Relationship Between Expansion Valve and Refrigerant Compressor

Let’s start by explaining the relationship between compressors and expansion valves.

The easiest way to determine which expansion valve you should choose for your HVAC is to know what the compressor types are or to know how to select the right compressor.

Let me explain why. An inverter compressor can maintain a consistent temperature without fluctuation, which ensures extended comfortability.

An inverter-type compressor runs at different speeds to always maintain a constant temperature, so when your temperature is at its highest stage, an inverter compressor doesn’t stop the motor.

Instead, it slows down the cooling process, which means it provides different temperatures to keep the highest temperature in the room and ensures comfort.

Consequently, the control logic of inverter compressors is more complex.

On the other hand, a fixed-speed compressor follows the start and stop mechanism.

When the temperature is highest, turn off the compressor motor and start again when the temperature drops.

So, fixed frequency compressors have a simpler control logic.

For example, an inverter compressor is used in air conditioner compressors, heat pumps, or refrigerators for better air quality, better temperature control, and saving energy consumption.

However, fixed-speed compressors are used in any application where the air temperature demand is constant, the budget is lower, and need to keep the maintenance and repair costs low.

According to the working mode of the inverter compressor and fixed frequency compressor, we know that the inverter compressor has a wide range of frequency variation, so it needs to use an electronic expansion valve. (Read what is electronic expansion valve to know why)

Fixed-frequency compressors have a fixed frequency range, so it is sufficient to use a thermal expansion valve or capillary expansion valve. (Read what is thermal expansion valve and what is capillary expansion valve to know why).

An inverter compressor uses an Electronic Expansion Valve – EEV and a fixed-speed compressor valve uses a Thermostatic Expansion Valve – TXV.

It’s obvious which expansion valve to choose if you know the compressor type that your application is using.

Relationship Between Expansion Valve and Refrigeration Unit

Before understanding the relationship between expansion valves and refrigeration units.

It is important to understand “What is an Internal and External Equalizer Expansion Valve“, “the Difference between a thermostatic expansion valve and an electronic expansion valve“, “the Difference between a Thermostatic Expansion Valve and a Capillary Tube” and “Refrigeration Unit Types“.

Refrigeration Units can be divided into cold storage units, commercial refrigeration units, transport refrigeration units, small units, chillers, quick freezing units, outdoor condensing units, indoor condensing units, and so on.

Cold room refrigeration units include walk-in cooler refrigeration units, semi-hermetic condensing units, freezer condensing units, monoblock refrigeration units, etc.

It is usually chosen with fixed frequency semi-hermetic compressors (Bitzer, Frascold, Refcomp, Carlyle, Bock, Dorin, etc.) and thermostatic expansion valves, because the temperature of the cooler is constant, and this is the most economical solution.

Small refrigeration units include self-contained refrigeration units, remote condensing units, drop-in refrigeration units, mini condensing units, DC condensing units, etc.

These types of units have a very small refrigeration capacity, so the use of capillary tubes is sufficient.

Commercial refrigeration units include outdoor condensing units, indoor condensing units, Secop refrigeration units, Embraco refrigeration units, Maneurop refrigeration units, Tecumseh refrigeration units, Horizontal refrigeration units, etc.

These types of units usually use reciprocating compressors (Secop, Embraco, Kulthorn, Maneurop, Horizontal, SAMSUNG) and their application environments are also more complex.

so thermostatic expansion valves or capillary tubes can be used in the selection of expansion valves, which should be combined with the application environment and the type of compressor.

This depends on the application and the type of compressor.

Relationship Between Expansion Valve and Air Conditioner Unit

Air Conditioner Units can be categorized into Central Air Conditioner Units and Split Air Conditioner Units.

A central air conditioner unit is also called a VRV or VRF unit. It is generally responsible for the cooling and heating of multiple rooms.

Therefore, it requires a fixed frequency compressor with a larger cooling capacity, e.g. Copeland scroll compressor, Hitachi scroll compressor, Panasonic scroll compressor, Daikin scroll compressor, SAMSUNG, etc.

Therefore, central air-conditioning units give preference to Thermostatic Expansion Valve when selecting expansion valves, e.g., Danfoss, Emerson, Sporlan, Saginomiya, etc.

Split air conditioner is the most common type of air conditioner and it is usually used in bedrooms, small offices, living rooms, etc. It is more common than VRV systems.

It requires less cooling capacity than VRV systems and has higher noise and comfort requirements.

Therefore, it is usually equipped with inverter rotary compressors (GREE, GMCC, Highly, Rechi, LG) which are much quieter.

Therefore, when choosing expansion valves for split air-conditioning units, preference is given to electronic expansion valves, such as Sanhua, STF, Dunan, Sina, etc.

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