Pressure switches are used on water pumps for the accurate control of the pump as it produces pressurized water. Without the use of the switch, the water pump would always be "on" or "off". However, with the pressure switch, the pump can be adjusted to turn "on" and "off" at predetermined settings to control the pump and subsequent pressure. By following a few basic procedures you can wire a pressure switch in a matter of minutes.
Switch off the power that feeds the pump circuit while you are wiring the switch. You can either switch "off" the circuit breaker or pull the fuse that controls the power.
Open the pressure switch wire box by removing the plastic or metal cover. Generally there is a thumbscrew mounted on top of the pressure switch to easily remove the protective cover. Some units may require the use of a screwdriver.
Use the wire strippers and remove the outer insulation from both the pair of power wires coming from the circuit control box and the pair of wires going to the pump motor. You will want to remove approximately one inch of the plastic insulation exposing the copper wire.
Using the wire pliers or the needle nose pliers and bend a half moon shaped curve in both sets of the wires. The curve will allow the bare copper end to fit cleanly under the screw head terminal of the pressure switch control.
Loosen the four screw terminals on the pressure switch and note that there are two sides to the contacts. Each side of the spring loaded contacts act like a simple switch. In other words the two contacts act like a double switch that open or close when the system calls for water pressure. Since the system is not pressurized, both contacts will be closed calling for the pump to be "on".
Attach one wire from the power feed circuit to one of the contact screw terminal heads. Attach one wire that is going to the pump to the screw head terminal that sets just next to the power wire. This will act like a single switch. Terminate the other set of contacts in the same manner. With the last power wire going to the second set of contact screw heads and the last pump wire going to the last screw head terminal.
Replace the plastic cover over the pressure switch and apply the power to the pump circuit. You should hear the water running into the system. Once the water pressure comes up to the factory setting the pump will shut off.