Electronic expansion valve (EEV)
Also known as: EEV, EXV
Short definitionAn expansion valve driven by a stepper motor. A controller calculates superheat from temperature and pressure sensors and moves the valve to exactly the opening required.
It does electronically what the thermostatic valve does mechanically. A temperature sensor and a pressure sensor are fitted at the evaporator outlet; the controller calculates superheat continuously and drives the motor. A mechanical valve needs 5–8 K of superheat, while an electronic valve can work with 3–4 K. A larger share of the evaporator surface does useful work, and hunting and liquid return are reduced.
It is preferred in supermarkets, multi-room plants and systems that run at part load for long periods. Combined with a control that lowers condensing pressure in winter, a 10–20% cut in annual consumption is typical. The controller, sensors and power supply go into the quote as well. A stepper motor stays where it is when the power fails; a backup supply or a solenoid valve in the line is provided so the flow can be shut off. In small, simple rooms a thermostatic valve is enough.