The forces that operate the valve are refrigerant head pressure, water pressure, and spring pressure. These forces oppose each other.
When the head pressure rises, and the refrigerant pressure overcomes the spring force of the pilot valve, the valve begins to open; the disk lifts off of the seat. This point is called the opening point.
You can adjust the opening point if you use the adjustment stem to increase or decrease the spring force. If the head pressure continues to rise, the refrigerant pressure further opens the valve until the valve is fully open. The range from the opening point when the valve lifts off the seat to the point when the valve is fully open is called the throttling range.
The throttling range is fixed and you cannot adjust it. The throttling range is approximately 40 psig for the low-pressure V43 Series valves, approximately 50 psi for the medium-pressure V43 Series valves, and approximately 60 psi for the high-pressure V243 Series valves.