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.
BACK-SEATED
• 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.
FRONT-SEATED
• 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.
MID-SEATED
• 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.
CRACKED
• 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.
