A: Yes, this would work. However, we would recommend purchasing our 20/40 pressure switch (item # PS2040). That way, you would only need to adjust the small screw (the range differential), instead of adjusting both the small screw and the big screw (the on/off pressure). To adjust the small screw differential down 10 PSI, you will turn the screw just under 3 revolutions (each turn is approximately 3.5 PSI). Also, ensure that your 1/4 HP pump can reach 30 PSI, or else the switch will never shut the pump off. Finally, if setting it to 20/30, ensure the air pressure in your pressure tank (drained of all water first) is set to 18 PSI (pressure tanks always need to be 2 PSI below the cut-in pressure of the switch).
A: I think you mean spring large and small. The large spring changes the cut in and cut out pressure together. The small spring changes the cut out only.
A: The auto off lever is tripping when the pressure drops to 10 PSI below of the normal off pressure (so in your situation, your pressure is dropping to 20 and tripping). This could be a sign that there is another issue in your system causing this drop in pressure. It is a safety measure to protect the pump from burning out. However, if this has not been an issue for you in the past, you may want to go back to a standard switch. You can adjust the off pressure of 30 (up or down), but the auto tripping will always be 10 PSI below it. You can call us at 844-251-7446 for further explanation.
A: It is pressure adjustable. To fix this problem raise the cut in pressure 2 or 3 pounds.