The following table shows the correspondence between port numbers and port letters for both styles of 3-way solenoid valve:Īnother way to think of this labeling is to consider port 1 the common, port 2 the normally-closed, and port 3 the normally-open, in a manner similar to SPDT (form-C) electrical switches.Īgain, bear in mind that the words “open” and “closed” do not mean the same for fluid valves as they do for electrical switches.Ī “normally-open” port on the valve permits fluid flow in its “normal” state, whereas a “normally-open” switch contact prevents electric current flow in its “normal” state.Īs with 2-way solenoid valves, the arrows denote preferred direction of fluid flow. However, the numbers do not consistently refer to pressure source (P) and exhaust (E) ports, but rather to the 3-way valve’s “normal” versus “actuated” statuses.Ī 3-way valve will pass fluid between ports 1 and 3 in its “normal” (resting) state, and pass fluid between ports 1 and 2 in its energized state. In all fluid power diagrams you will see that only one of the boxes on each spool valve will have lines connecting to it and/or labels at the fluid ports, and that box is the one which will be aligned when the valve is not being actuated.Īlternatively, the numbers 1, 2, and 3 may be used to label the same ports.

The letters used to label ports on a valve such as this not only denote those ports’ destinations, but also serve to mark which “box” of the valve’s symbol is the normal (resting) state. Tank rather than Exhaust): 3-way Solenoid Valve Schematics If the solenoid valve is intended for use in a hydraulic (liquid) system, the letter “T” is customarily used to identify the return port rather than “E” (i.e. Ports on a pneumatic 3-way valve are commonly labeled with the letters “P,” “E,” and “C,” representing Pressure (compressed air supply), Exhaust (vent to atmosphere), and Cylinder (the actuating mechanism), respectively.Īlternatively, you may see the cylinder port labeled “A” (for actuator ) instead of “C”. 3-way solenoid valves operate in a manner analogous to single-pole double-throw (SPDT) electrical switches: with two paths for flow sharing one common terminal.ģ-way solenoid valves have three ports for fluid, and like 2-way valves may be referred to either as normally-open and normally-closed.

3 way electric solenoid valve for water