A pressure switch is typically used to power an air compressor, which turns the compressor motor unit on and off. When an air compressor is installed in your garage, it will typically require 240V electrical power. Installing a pressure switch requires you to wire it to the motor on the compressor and from the line for power. However, you will first need to obtain the pressure switch to install for your compressor.
Turn off the power to the air compressor by turning off the breaker for the 240V outlet.
Locate the pressure switch that is on the storage tank for the compressor. You will see a pipe nipple on a 6 mm (1/4 inch) pipe that is used to transfer the air from the tank to the pressure switch.
Wrap the Teflon tape over the male ends of the pipe threads. Set the fitting for the pressure switch over the pipe nipple. Tighten the fitting by turning it clockwise with an adjustable spanner.
Take the top cover off of the pressure switch. You will see four contacts inside of the switch, each with its own screw connector.
Strip the four wires on the switch 1.2 cm (1/2 inch) with the wire strippers. Two wires going to the compressor motor and the other two are for power.
Connect the two wires for power to the terminal screws labelled "Line." Tighten the screw by using the screwdriver.
Connect the other two wires from the motor to the terminal screws labelled "Load." Tighten the screws by using the screwdriver.
Connect the bare copper wire to the green terminal screw that is on the frame of the pressure switch.
Set the top cover back on the pressure switch and then turn on the breaker. Move the pressure switch to the "On" position.
The pressure switch will need to be rated for the motor on the air compressor.
The factory settings on the pressure switch should not be adjusted, as it may cause damage to the air compressor.