How to Wire Irrigation Pump Relays
Some homeowners have the option of drawing irrigation water directly from a well, tank, pond or creek, rather than using the municipal source. In these situations, the control box that turns the irrigation valves on and off according to a set schedule needs to be wired to a pump relay. This device activates the pump that draws water from one of these alternative sources each time the control box turns on a valve. Most irrigation control boxes include a terminal for the wire that goes to the pump relay.
Disconnect the irrigation control box from its power source.
Mount the pump relay a minimum of 15 feet from both the irrigation control box and the pump, as electrical interference can occur if the devices are mounted in close proximity to each other. Use the installation hardware that comes with the pump relay to attach it to the wall of a garage or other location protected from the elements, unless it is a model designed for exterior mounting.
Connect the wiring to the control box. Route the two wires for the pump relay through one of the holes or knockouts in the bottom of the control box. Connect the white wire to the common terminal, marked with a "C" on most controllers. Strip off three-eighths-inch of the wire sheathing, unscrew the terminal screw, slide the wire behind the screw and re-tighten the screw. Repeat the procedure to connect the black wire to the terminal for the pump relay, often marked "P" or "MV."
Route the wires from the control box to the pump relay. If desired, use wire clips to attach the wire discretely to the wall so it is out of the way and visually unobtrusive; these are found at any hardware store and have a small nail attached to a plastic clip that is hammered into the wall to hold the wire in place.
Connect the wiring to the pump relay. Open one of the knockouts on the bottom of the relay box by placing the tip of a screwdriver against it and striking it sharply with a hammer. Route the wires through the knockout. Attach one of the sprinkler wires to each of the terminals labeled "24V."
Connect the wiring from the power source to the pump relay and from the pump relay to the pump. This wire must be enclosed in electrical conduit and installed by a licensed electrician. These are typically connected with wire nuts to the wires labeled "Power In -- L1 and L2" for those from the power source and "Power Out -- L1 and L2" for those that go to the pump.
Re-connect the power source to the control box and turn on the circuit that provides power to the pump relay. Manually turn on one of the valves to test the system. The pump should now come on whenever one of the valves is turned on by the controller.
- Wire strippers
- 24-volt wire
- Wire clips
- Electrical conduit
- 120- or 220-volt wire
- Wire nuts
- Check with local authorities regarding the use of water from rivers, lakes, streams and artificial impoundments for irrigation purposes, as property owners do not always have the right to use the surface water that passes through their property.
- Do not mount the pump relay box in direct sunlight to prevent overheating.
- Models may vary in their exact configuration and labeling. Follow the instructions that come with the product for more specific installation details.
- The wire from the controller to the relay should be rated between AWG 16 and AWG 24 and is used to carry a 24-volt current. The wire from the power source to the pump relay, as well as the wire from the pump relay to the pump, needs to be rated AWG 12 and will be used for a 120-volt or 220-volt current, depending on the pump model. Make sure to use a relay that is compatible with the voltage of the pump. This should be on a dedicated circuit and must be installed by a licensed electrician.
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