The valve positions used in this description are defined as follows:
Back-Seated – Valve stem turned all the way out (fully counterclockwise).
Front-Seated – Valve stem turned all the way in (fully clockwise).
Mid-Seated — Valve stem turned halfway between back-seated and front-seated position.
Cracked — Valve stem turned about one turn clockwise from the back-seated position.
NOTE: The port numbers shown have been arbitrarily assigned for the purpose of this description.
• Used for normal (non-service) system operation. Flow of the system refrigerant is through the valve via ports 1 and 2. The direction of refrigerant flow depends on valve placement (low side or high side) in a system. The service port is completely closed off.
• Path between port 1 and port 2 is dosed, resulting in no refrigerant flow through the valve.
• System components on the port 1 side of the valve are isolated from those on the port 2 side.
• Provides access to the system via the service port and port 2. This allows the measurement of the system pressure that exists on the port 2 side of the valve. It also makes the system components on the port 2 side of the valve accessible for the purpose of evacuation and refrigerant recovery or charging.
• Flow of refrigerant is through the valve via ports 1 and 2.
• Provides access to the system through the service port and ports 1 and 2.
This allows measurement of the system. It also allows access to the system components on both sides of the valve for the purpose of evacuation, recovery, and charging.
• When cracked, the service port is opened to the system. This position is used only if a pressure reading is required. One clockwise turn from the backseated position is enough to crack the valve for this purpose.