To automate the control of the pump you simply replace the manual switch in the circuit with an automatic switch. There are several types commonly used.
Types of Automatic Pump Switches:
• Timer. Any electric timer can be used to turn the pump on and off at predetermined times. A relay is used to start and stop the high voltage pump using a low voltage timer, like a standard irrigation controller. With the right voltage relay, you could even hook the pump up to your computer!
• Pressure Switch. Most well pumps are controlled by a pressure switch. The pressure switch turns on the pump when the pressure drops in the pipes, and turns it back off when the pressure gets too high. A typical installation will have a pressure tank which stores pressurized water so that the pump doesn’t cycle on and off rapidly due to pressure changes. The tank acts as a reservoir to stabilize the pressure in the system. Most pressure switches are adjustable, you can modify the on and off pressure settings within a limited pressure range, usually 20 to 45 PSI.
• Irrigation Controller. Most irrigation controllers have a pump start circuit built into them. You simply connect the wires that go to the switch in the diagram above to the controller pump start terminals, and the irrigation controller will turn the pump on whenever it turns on a valve. Do not hook up the controller to an existing relay circuit. In other words if your pump already has a low voltage starter circuit with a relay you will need to install a new one for the irrigation controller. The controller has its own 24 volt AC power source, so if you hook it up to an existing circuit the irrigation controller may be damaged. If you don’t understand electrical circuits get an electrician to wire it for you!
• Flow Switch. Flow switches are sometimes used on booster pumps. When the switch detects flow in the pipes it turns on the pump. So if you open a sprinkler valve, the water would begin to flow, and the pump would come on. This only works if the water is already pressurized and you want to use the pump to increase the pressure. An example would be a sprinkler system hooked up to the local water company pipes that needs more pressure than the water company provides.
• Combination of one or more of the above switches. It is very common to combine one or more of the switches above so that the pump is turned on or off by any of several different events. A very common application is one relay controlled by both a pressure switch and a manual override switch, and a second relay operated by the irrigation controller. I often will add a flow switch to the irrigation controller relay, setting it to turn OFF the pump if there is no flow. For example, if one of the automatic valves fails to open when the controller tells it to, the irrigation controller would force the pump to continue running, even though there was no water flow! The pump would then over heat, since it uses the continuous flow of water through it to remove the heat, and the bearings would melt.