Two-wire too late
14 Sep, 2011 By: Christine Hawkins i-newsJust a few years ago, I was hip-deep in a muddy hole, sorting through a bundle of irrigation wires. Thirty-two valve wires had been severed and reburied when a contractor installed a concrete path through my customer’s lawn. The next week, I was doing the same with a bundle of wires torn from the ground by the roots of a toppled pine tree.
You’ve been there: When a customer calls and complains that the lawn is dry, or suddenly you notice that a valve is not firing like it used to. You go to the usual suspects. Did someone turn off the water? Do we have enough pressure? Is it the diaphragm? The solenoid? Is my controller malfunctioning? The last thing any of us want to get into (or admit to) is a faulty wire. We like to think that our wire is unassailable, safely underground and out of sight. Indeed, wire can have a long life if left undisturbed in its earthly bed. But the truth is that for many of us, faced with errant shovels, falling trees and burrowing rodents, wire can be the Achilles’ heel of our irrigation systems.
Wouldn’t life be simpler if we could use less wire?
Until technology advances to where we can reliably activate valves with just a twitch of a neuron, we have the next best thing: Two-wire. Using just a fraction of the copper wire that conventional systems require, two-wire systems not only reduce installation labor, but also provide versatility and simplicity to even the most complex projects.
You may have even heard of this miraculous technology before; it’s certainly not the new kid on the block. But, just in case, here are the basics.
Conventional systems require that a dedicated electrical circuit, consisting of one “hot” wire and one “common” wire, activate each solenoid. In a system with 25 valves, that’s a minimum of 26 wires runs from the controller to the field; 25 “hot” wires and one “common” wire. If the valves are evenly spaced along a 1,000-ft. mainline, that can mean as much as 14,000 ft. of wire is needed to run from the controller to the valves.
The two-wire difference
In a two-wire system, a decoder with a unique electrical signature or serial number is wired into each solenoid. A wire path consisting of (you guessed it) two wires is installed from the controller to each decoder in the field. To operate a solenoid, the controller sends a message along the wire path to a specific decoder, much like making a phone call. The decoder receives the signal meant for it alone, interprets the data, and then completes the electrical current to operate the solenoid.
For a system of 25 valves with a 1,000-foot mainline, installation would require only 1,000 ft. of wire and 25 decoders.
From an installation standpoint, this can significantly reduce your labor and materials cost for new irrigation systems. As the costs of copper and labor increases, most systems that are upward of 25 valves, or even less, are more easily and effectively installed as a two-wire system. Installation of phased projects is vastly simplified, as no additional wires are required to expand the system: Simply extend the two-wire path into the new project phase to connect any new devices.
Two-wire systems can provide a host of benefits not only in the installation of a system, but also in the design and maintenance. When a trencher has sliced open a wire path, would you rather splice together 40 individual wires or simply repair one two-wire path? If the wire does fail, would you rather track 14,000 ft. of wire or just the few hundred feet between decoders? Many of today’s two-wire controllers also come with internal diagnostic tools to assist you in the field.
Designers also have come to appreciate the flexibility of modern two-wire systems, as these controllers not only communicate with the valves along a two-wire path, but also connect additional devices such as flow sensors, master valves and pump starts without running additional wires from the controller to these devices.
If you have been paying attention to industry publications over the last several decades, you have seen articles touting the benefits of two-wire. I agree with all of them, and yet, many of you and your colleagues may not have given them a second look. I would encourage you to do so.
As resources like copper, water and labor are strained, our industry will have to do more with less. Vendors today are offering systems with greater capabilities to simplify installation and maintenance. Advances in technology and software allow two-wire controllers to respond to the changing way we manage our landscapes. I have worked with two-wire for years and have found that my customers appreciate the versatility that this modern technology brings to their projects.
The only thing many of them (and I) regret is not knowing more about the convenience and versatility of two-wire systems sooner. Contact your local distributor to learn more.
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