A valve for a refrigeration system comprising: a valve body having an inlet port, an outlet port, and walls forming a main cavity; a cartridge configured to reside within the main cavity and having a piston configured to travel in a first direction to permit fluid flow from the inlet port to the outlet port and in a second direction to impede fluid flow from the inlet port to the outlet port; a port plate configured to removably couple to the valve body to substantially close an end of the main cavity substantially enclosing the cartridge within the main cavity, the port plate including a plurality of ports (26a, 26b, 26c), each port (26a, 26b, 26c) configured to accept at least one of various valve control elements configured to control the piston to permit or impede the fluid flow from the inlet port to the outlet port; and the valve characterised by a manual opening mechanism including a valve stem and configured for manually moving the piston to permit or impede the fluid flow from the inlet port to the outlet port, wherein at least a portion of the manual opening mechanism extends through an opening in the port plate that is in axial alignment with the piston, wherein the cartridge residing within the main cavity becomes accessible without disconnecting the valve from the refrigeration system by removing the port plate from the valve body, and wherein each port (26a, 26b, 26c) is disposed at an acute angle relative to a central axis of the piston thereby allowing access to fasteners of the port plate such that the port plate is removable from the valve body without removal of the control elements from the ports (26a, 26b, 26c). a valve body having an inlet port, an outlet port, and walls forming a main cavity; a cartridge configured to reside within the main cavity and having a piston configured to travel in a first direction to permit fluid flow from the inlet port to the outlet port and in a second direction to impede fluid flow from the inlet port to the outlet port; a port plate configured to removably couple to the valve body to substantially close an end of the main cavity substantially enclosing the cartridge within the main cavity, the port plate including a plurality of ports (26a, 26b, 26c), each port (26a, 26b, 26c) configured to accept at least one of various valve control elements configured to control the piston to permit or impede the fluid flow from the inlet port to the outlet port; and the valve characterised by a manual opening mechanism including a valve stem and configured for manually moving the piston to permit or impede the fluid flow from the inlet port to the outlet port, wherein at least a portion of the manual opening mechanism extends through an opening in the port plate that is in axial alignment with the piston, wherein the cartridge residing within the main cavity becomes accessible without disconnecting the valve from the refrigeration system by removing the port plate from the valve body, and wherein each port (26a, 26b, 26c) is disposed at an acute angle relative to a central axis of the piston thereby allowing access to fasteners of the port plate such that the port plate is removable from the valve body without removal of the control elements from the ports (26a, 26b, 26c).