The incorrect installation of the thermostatic expansion valve and its external equalizer.
It is an essential part of the refrigeration cycle. Its function, based on temperature and pressure, is to open or close the valve to regulate the flow of the refrigerant in order to:
Expansion Valve
- Reduce the pressure of the liquid refrigerant to the evaporator pressure.
- Control the refrigerant flow rate to match changes in the heat load.
- Maintain a constant superheat to ensure the refrigerant is fully converted into a gaseous state.
Selection of Evaporator Units
Incorrect placement of the equalizer and sensor causes the valve to operate improperly, leading to liquid refrigerant returning to the compressor, frost formation on the compressor, and other issues.
The mistake occurs when the sensor and equalizer are not positioned on the same side, or when the sensor is installed after the equalizer, or when the sensor bulb faces the evaporator, as shown in the illustrations.
To avoid this mistake, the sensor and equalizer should be positioned and installed as follows:
- The sensor should be installed according to the pipe size, as follows:
- When the pipe size is 7/8 inch or smaller, the sensor should be positioned at the 12 o’clock direction.
- When the pipe size is 7/8 inch or larger, the sensor should be positioned at the 8 o’clock or 4 o’clock direction.
In all cases
- It should be insulated from external temperatures.
- When the pipe size is 7/8 inch or smaller, the sensor should be positioned at the 12 o’clock position.
- The sensor should be installed at the closest point to the evaporator outlet.
- The sensor should be installed at the closest point to the equalizer line.
Most of us know that the thermostatic expansion valve or any type of expansion valve is an essential part of the refrigeration circuit, just like the compressor, condenser, and evaporator.
The main purpose and function of the thermostatic expansion valve is to reduce the pressure of the liquid refrigerant to the evaporator pressure and to control the flow rate to match changes in the heat load. It also maintains a constant superheat to ensure that the refrigerant is fully converted into a gaseous state.
The expansion process depends on temperature and pressure, as the valve opens or closes accordingly to regulate the refrigerant flow through an orifice with various sizes selected based on the system’s requirements.
The pressure and temperature are read by a bulb sensor and an external equalizer.
If the equalizer or bulb is installed in the wrong location, it will give incorrect readings that do not reflect the actual needs of the refrigeration system. As a result, the valve will regulate improperly, leading to several issues such as:
* Liquid refrigerant returning to the compressor,
* Frost formation on the compressor, and other related problems.
The main installation error occurs when the sensor and equalizer are not positioned on the same side, or when the sensor is installed after the equalizer, or when the bulb head faces the evaporator, as shown in the illustrations.
Incorrect installation of the Expansion Valve and its External Equalizer.
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