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Many sprinkler systems require that the timer supply power to a relay in order to send power to a sprinkler pump. Often the sprinkler system is using secondary water and is not connected to the culinary water running to the house. And many times the secondary water is supplied at very low pressures requiring the addition of a sprinkler pump.
The way this works is:
- The wires from the relay are connected to the master valve circuit on the timer (see photo). One wire to the MV or master valve terminal, and one wire to the common terminal. When the timer activates it sends power to the relay.
- When the relay receives power it closes the contacts and power is then sent to the pump to activate. Most pumps are pre-wired for 230 volts, but the selector on the pump can be changed to use 110 volts. It is very important when wiring a pump to be certain which is being delivered to the pump, 110 or 230 volts. If the wiring is wrong you could end up burning up a pump, and they are not cheap. A common 1.5hp sprinkler pump can run as much as $400-$600. Yes I know you can buy one from the home improvement stores for $199, but my experience is that they only last a few years and then the expense of a new pump and installation costs start all over again.
- At the same time the timer/controller is sending power to the sprinkler pump, it is also sending power to the sprinkler valve and opening the valve. So when the pump pressures up the system the sprinkler zone is open and waiting for the water.
- When the cycle is complete and the timer shuts off the power to the sprinkler valves, it is simultaneously shutting of the power to the relay and the pump. It varies from timer to timer, but most Master/Pump circuits are on by default on the sprinkler timer/controller.
- Below is a typical drawing and description of a Hunter SRC series timer Master/Pump valve wiring. Most sprinkler timers will be similar to this example.
- Route wires from the master valve or pump start relay location into the controller with the valve wires.
- Connect either wire from the pump relay to the MV terminal. Connect remaining wire to the C (common) terminal.
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