Introduction to Electric Three-Way
and Electric Four-Way Valves
Principles and Applications
Electric three-way and electric four-way valves are important flow control components, widely used in HVAC systems, electric vehicles, heat pump systems, battery thermal management systems, and industrial fluid control. They are electrically driven to regulate the direction, mixing, or distribution of fluids such as water, coolant, refrigerant, or glycol.
Electric Three-Way Valve
Working Principle
An electric three-way valve has three ports and an internally movable valve core (spherical, plug, or slide valve). It is driven by an electric actuator (motor-driven or stepper motor-driven) that rotates or moves the valve core to change the flow direction of the fluid.
There are two main functional types:
• Diverting Type (Flow Switching Type)
One inlet → Two outlets
This valve directs fluid from one source to one of two different loops.
• Mixing Type
Dual inlets → Single outlet
This valve mixes two fluids at different temperatures to achieve a target output temperature.
The actuator receives control signals (ON/OFF, PWM, or CAN communication) and adjusts the valve position accordingly.
Applications of Electric Three-Way Valves
1. Electric Vehicle Thermal Management
Switching coolant between the battery and motor circuits
Mixing hot and cold water to control battery temperature
Directing coolant to the cabin heater core or bypass circuit
2. Heat Pump Systems
Switching between heating and cooling circuits
Mixing return water to maintain a stable supply of water temperature
3. HVAC Systems
Zone temperature control
Mixing hot and cold water in central heating systems
Electric Four-Way Valves
Working Principle
Electric four-way valves have four ports and are primarily used to change the direction of fluid flow. Internally, they use a spool or rotary valve core controlled by an electric actuator. The actuator changes the internal flow path configuration, enabling the system to reverse the circulation direction of the refrigerant or coolant.
Applications of Electric Four-Way Valves
1. Heat Pump Reversing Function
This is the most common application. In air-source heat pumps:
Heating mode: Refrigerant flows from the compressor through the condenser → expansion valve → evaporator.
Cooling mode: The four-way valve reverses the refrigerant flow direction.
This allows a single system to provide both heating and cooling functions simultaneously
2. Electric Vehicle Heat Pump Systems
Switching between cabin heating and cooling modes
Optimizing refrigerant flow path in the integrated thermal management system
Modern electric vehicle platforms integrate the battery, motor, and cabin thermal management system. The electric four-way valve enables:
High-efficiency heat recovery
Mode switching
Improved energy efficiency in winter
