The EEV is the electronic version of the thermostatic valve. Superheat is calculated from temperature and pressure sensors at the evaporator outlet, and the controller drives the valve with a stepper motor to the required opening between 0 and 100. Where a mechanical valve has to work with 5–8 K of superheat, an EEV can work with 3–4 K; this means a larger part of the evaporator is used effectively and the condensing pressure can be lowered.
The gain shows in numbers: together with floating head pressure control (lowering condenser pressure in winter), a 10–20% reduction in annual energy consumption is typical. The valve adapts to capacity changes and different refrigerants through software; it prevents overload after defrost, liquid floodback and hunting. Superheat values are logged by remote monitoring systems.
In return it needs a controller, sensors and a power supply; when power fails the valve closes (no pump-down needed) or stays open on a backup supply. In small, simple rooms the TXV is still economical and adequate; for supermarkets, multi-room plants, systems that run for long periods at part load and every business where energy cost matters, the EEV is the right choice.