These advanced design, strong bodied, precision manufactured solenoid valves control the on-off flow of refrigerant. They are superior in their ability to overcome dirt and sticky oil during opening and closing, and operate smoothly even in an oil-free “dry” system. When electrically energized, the upstream pressure is ported through the pilot solenoid to the top of the piston to push it downward and open the main valve seat wide; when de-energized, pressure is no longer ported to the top of the piston and a spring closes the main valve seat to stop flow in the arrow direction on the valve body.