A thermal and electronic expansion valve are both HVAC components that control the refrigerant amounts and regulate the superheat.
However, there are some differences between these two common types of expansion valves(what are the different types of expansion valves).
The significant difference between a TXV and an EEV is that a thermostatic expansion valve is a mechanical device.
In contrast, an electronic expansion valve is a programmable device that optimizes the required performance.
Please review what is expansion valves to better understand the structure.
An electronic expansion valve has some additional parts to make it run, for example, the controller and sensor;
On the other hand, a thermostatic expansion valve doesn’t have any extra components.
The working principles of both of these valves are also different.
A TXV senses the temperature with a liquid-filled sensing bulb, and the gas pressure on it forces it to open the TXV.
This force decreases when the temperature drops and adjusts the refrigerant flow.
Expansion valves of either type regulate refrigerant flow by sensing the degree of superheating and subcooling in the system.
Check what is superheat and subcooling to know more.
On the other hand, in an electronic expansion valve, the sensor first collects the data, then commands the controller, and does what the software is programmed to do.
EEV can control the refrigerant flow with more precision than a TXV.
That’s why it is widely used in HVAC units where mass flow needs a change of high rates and requires accurate temperature control.
Sometimes, people ask us if an EEV is more efficient than a TXV. The answer is not most of the time.
The efficiency of an EEV depends on how good the program’s algorithms are, which will dictate its operation.
Please review how expansion valves work to better understand the difference in expansion valve efficiency.
5. Control logic
The TXV control logic is based on the current state of the control point.
Still, the EEV control logic is based on the different types of programmed intelligent control devices that can’t adjust the current state.
Different types of expansion valves are due to different application requirements.
Thermostatic expansion valves are used in semi-hermetic condensing units, transport refrigeration units, commercial refrigeration units, commercial outdoor condensing units, cold room refrigeration units, heat pump drying machines, swimming pool heat pumps, etc.
Electronic expansion valve is used in VFV, VRF air conditioners, split air conditioners, cold water and hot water units, inverter refrigerators, inverter heat pumps, etc.
|Thermostatic Expansion Valves
|Electronic Expansion Valve
|Slow response speed
|Fast response speed
|Remote control is not possible
|Remote control is possible
|Efficiency is high
|Efficiency is low.
|Small flow rate adjustment range
|Large flow rate adjustment range
|Low adjustment accuracy
|High regulation accuracy
|Inconvenient adjustment of superheat
|Easy adjustment of superheat