12 volt solenoid valves are available in direct current (DC) and alternating current (AC) versions.   Most 12V DC solenoid valves are of the 2-way type used for the simple on/off control of water, air, petrol/gasoline or diesel fuels or gases such as butane or propane.  Because this voltage is compatible with vehicle electrical systems they are popular for automotive or marine use.  12v AC or DC valves may also be found in domestic showers and public display systems such as water fountains and water curtain display systems, although ultimately powered by the mains AC supply this type of equipment will use a power supply to provide a 12v supply for the solenoid valves, thereby reducing any possible safety risk by separating a potentially hazardous high voltage from the water.

In the case of a normally closed (fail-safe closed) solenoid valve when 12 volts is applied the solenoid valve opens allowing flow. When the 12 volts are removed from the solenoid valve then the valve will automatically close and prevent flow along the pipe. For a normally open solenoid valve then the opposite is true, i.e. the solenoid valve fail-safe position is open and when power (12v) is applied the solenoid valve will power close. 12 Volt solenoid valves are typically found

With a 12v 3/2 (3 port/ 2 position) solenoid valve the valve has 3 ports, typically 1 inlet port and 2 outlet ports for diverting flow or two inlets and one outlet for mixing flow. Diesel to vegetable oil car conversion systems will use both these styles of valves.

For operating a much bigger valve such as a pneumatically operated angle seat piston valve or a pneumatic cylinder, most commonly a 3-way normally closed valve will be used, this valve has a single inlet and an outlet.  The third port acts as an exhaust, the outlet is connected to the pneumatic cylinder, when energised the outlet port opens allowing air into the cylinder, when the valve is de-energised the air supply is cut-off and the outlet port is now connected to the exhaust port allowing air to escape from the cylinder or actuator.
Most solenoid valve suppliers will wind coils to different specifications to operate on AC or DC, some manufacturers do produce AC/DC rated coils.  Because this involves a compromise in the specification of the coils’ windings, this has the disadvantage that when used on DC the power consumption of the coil is higher leading to the coil operating at a higher temperature.     

Beta Valve stock a wide range of both 12v AC and 12v DC solenoid valves with the valve bodies produced in brass, plastic or stainless steel.

12V solenoid valves for water

  12V valves for potable water (drinking water) WRAS approved.

12V solenoid valves for light oils

12V solenoid valves for gas

12V solenoid valves for steam

12V solenoid valves for air