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Two-Wire Makes Irrigation Too Easy

REBECCA PETERSON | Controllers

A recent newsletter reported that the price of copper is so high that people are actually stealing it. Because copper prices have increased almost 160 percent since 2005, copper has been stolen from utility poles, plaques, and irrigation systems, and then sold for profit

With the price of copper high enough that it’s worthwhile to steal, now would be a great time to try to use less of it. The problem is that irrigation systems need copper wiring, and a lot of it. One of the benefits of an irrigation system using two-wire technology is that the amount of wire used is greatly reduced.

Two-wire isn’t a new technology. It’s been used in the international market for years, and arrived in the U.S. more than three decades ago. Unfortunately, those early two-wire systems left something to be desired. They used DC current, and weren’t very reliable. The experience left many people with a bad taste in their mouths, and the concept of two-wire faded from the American market.

Luckily, things change. The technology was redeveloped using AC current, and the systems became just as reliable as standard wiring systems. However, while two-wire has come to dominate the international market, contractors in the U.S. still aren’t very familiar with it.

Mitchell Flores, field supervisor for Gothic Landscape, Valencia, California, thinks more people should be. “It’s the system of the future,” he says.

What is two-wire technology? What makes it better than conventional wiring? For this article, let’s oversimplify what would be a typical installation. Imagine a landscape with a group of three valves that are 50 feet from the controller, another group of three valves that are 100 feet from the controller, and a final group of three valves that are 150 feet from the controller. To wire this system conventionally, you’d need one “common” or “ground” wire connecting the first three valves to the controller. Then, you’d need to run a 50-foot length of wire from each individual valve back to the controller. This makes four wires, total, for the first group of valves.

Another ground wire would have to run from the controller to the group of valves at the 100-foot mark. In addition, a 100-foot length of wire would have to connect each of the three valves individually to the controller. Once again, a total of four wires.

The final group of valves would also require a separate ground wire, and on top of that, another three individual lengths of wire connecting each valve all the way back to the controller. Each of those wires would be 150 feet long. Not counting the amount of wire needed for the ground wires, we already need more than 800 feet of wire to make this system run. With the ground, we’d need well over 1,000 feet of wire.

The way around this situation is the use of two-wire technology. Instead of each individual valve in the field needing to be connected back to the controller, a two-wire system works like a string of holiday lights.

With holiday lights, you plug one end into the outlet, and all of the lights on the string get power. With a two-wire irrigation system, the two wires together function as the string, the controller functions as the outlet and all of the valves in the field function as the lights. You plug one end of the “string” into the controller, and all of the valves on the string get power (and coded instructions telling them when to turn on and off). Only one valve needs to be connected directly to the controller, as opposed to every valve.

The system works using a series of decoders—one decoder for each valve. Each decoder translates the signals it receives from the controller, and then the decoder controls its valve, turning it off or on as necessary. You’re trading a small decoder in each valve box for the hundreds—or thousands—of feet of wire a conventionally-wired system requires. “You can save more than 80 percent on wire,” says Paul Cordua, president of HIT Products, Lindsay, California. “Two-wire technology makes it possible to spend $200 on wire instead of $1,000.”

With savings like this, the use of two-wire is growing. “In the next couple of years, two-wire technology is really going to come into its own,” predicts Larry Sarver, president of Tucor, Wexford, Pennsylvania. “There’s going to be a broader acceptance of the technology. Commercial applications especially will all be done with two-wire.”

More mainstream manufacturers are already jumping onboard. While two-wire was seen as risky and unreliable a few decades ago, it’s now being regarded as “the next big thing.” More manufacturers producing two-wire systems can only be a good thing for the technology, as the range of competing products available will drive the price down.

Rain Master, Simi Valley, California, is one of several companies jumping onboard to release a two-wire system. “The technology has gotten to the point where the problems have disappeared,” says Steve Springer, vice president of business development. “The wiring issues that were prevalent years ago have been solved. That’s why we’ve decided to release our two-wire system: because today’s two-wire systems offer you every benefit imaginable, and few, if any, drawbacks.”

Savings on wire is an obvious advantage. However, flexibility and expandability are also major considerations, as well as troubleshooting a system when a wire breaks.

If it becomes necessary to add to a conventionally-wired irrigation system, any new valves would need to be wired directly to the controller. The trenches to accommodate the wiring from the new valves all the way back to the controller would be time-consuming to dig, and could mar the look of a previously completed portion of the landscape.

Two-wire eliminates these problems. Valves can be added easily to a two-wire system without running any new wires back to the controller. Picture splicing a second string of holiday lights into the middle of an existing string, making a T shape. It’s that simple. You can splice into the existing two-wire path anywhere, install new valves and more decoders, and a whole new area of the landscape is wired for irrigation. The new valves can function without being directly connected back to the controller.

In a standard system, the many wires from the valves to the controller are often color-coded for easy identification—red for valve number one, blue for valve number two, etc. These multiple color coded wires are usually in a waterproof casing, making it easier to work with the wires. The problem is that, in larger installations, there just aren’t enough colors for each valve to get its own. Furthermore, after being in the ground for a period of time, colors can fade.

In the example given earlier of a conventional system, the four wires running 50 feet from each valve to the controller might all be grouped in a bunch and buried together. This would be done so that a contractor isn’t digging four individual trenches to the controller. But what if a backhoe blade comes through, and snaps all four of the wires? The colors are so faded, you can no longer tell what gets connected to what. You have to test each individually to figure out what valve goes with what wire.

This doesn’t sound so bad, because in the example, only four wires were broken. But what if it’s a larger property? What if a bundle of 100 wires got broken? Testing and repairing those wires could take hours. At this point, a two-wire system would start sounding pretty good. Instead of 100 wires to repair, how about only having two?

The nice thing about the backhoe blade here is that you can tell right where the wires are broken—the broken wires are dangling, frustratingly, off the teeth of the backhoe blade. But what if a wire in a standard system corrodes over time, becomes brittle, and breaks while it’s underground? What if that wire belongs to one of the valves that are 150 feet from the controller? You’re left digging a 150-foot trench, trying to find where on the 150-foot length of the wire the break is located. Because a two-wire system is connected like a string of holiday lights, the problem is always between the last working valve and the first non-working valve.

This is one reason that Chris Himes, director of purchasing for Norman’s Nursery, San Gabriel, California, likes two-wire technology: “With a standard system, it can be hard to locate a break in the wire. You can end up doing a lot of digging. With two-wire, problems are much easier to pinpoint.”

Norman’s Nursery was introduced to two-wire by a supplier who brought a rep in from a two-wire manufacturer to talk about the system. “It sounded like it would be easy to install and maintain. It also sounded like it would save us money because we’d use less wire,” Himes says. Norman’s Nursery tested the system, and loved it. Now, all of their growing grounds—around 1,200 acres—use two-wire systems.

Two-wire can also give you fewer controllers to maintain. Wire for a standard irrigation system can usually run about 2,500 feet. That means, on a large property, that once you reach the 2,500 foot mark, you’ll have to install another controller. You could end up using two controllers, or three, or more. Some two-wire systems, on the other hand, can run for up to six miles. On an application that would usually require two or three controllers, you’ll only have to use one. You’ll have one controller to program, and if something goes wrong, one controller to troubleshoot.

“A two-wire system is also capable of passing richer information,” says John Fordemwalt, president of Baseline, Boise, Idaho. The wiring of conventional controllers transmits only power. When a valve needs to turn on, the controller gives it power, when it needs to turn off, the controller cuts off power.

However, a two-wire system doesn’t just transmit power, it can also transmit data. This means that some two-wire systems can not only be hooked up to valves, but also to moisture sensors, weather stations, or flow sensors.

Information isn’t just sent on a one-way path from the controller into the field. The controller is also capable of receiving information back from the field. This makes troubleshooting easier. If a component fails, an intelligent two-wire system can tell you whether it was the fault of a solenoid or wire.

twowire3.jpg
Converter allows additional controller output to be converted to two-wire output.

Creating the system
Starting to install two-wire systems doesn’t necessarily mean that you’ll have to become familiar with an entirely new set of controllers. If you like the controller you’re already using, many can be converted to two-wire output. This allows a contractor to program with the platform he’s already mastered, so he won’t have to spend time learning a new one.

For some systems, switching to two-wire technology is as simple as popping in a new module or two. You don’t even need any tools—just swap in a two-wire module for the conventional module you’re already using.

Other manufacturers offer an adapter than can convert a standard controller to two-wire output. This is helpful for the many landscape companies that standardize and work with only one kind of controller. An adaptor works in conjunction with a standard controller to create a two-wire system. A company can use the controller of its choice, and still get the benefits of two-wire technology. This means the company won’t have to spend time training employees on an entirely new system. Furthermore, jobs won’t be slowed down as workers struggle to operate a system they’re not familiar with.

An element of two-wire that you need to be careful with are your wire connections. They have to be done properly. If the connections aren’t good, you could end up in a situation where the system is able to transmit only power, and not code.

“A two-wire system is only as good as the wire selected, the installation, and the earth grounding,” says Dave Shoup of Hunter Industries, San Marcos, California. Some manufacturers recommend that for splices, instead of simply burying the splice, you leave some slack and put it in a valve box. The slack will protect the integrity of the splice through the stresses of freeze/ thaw cycles, and the valve box will make it easier to find the splice if there’s ever a problem.

“Two-wire technology has really caught on in the East, and is now working its way toward the West Coast,” says Sarver. “In Florida, about 70 percent of the larger systems being installed use two-wire technology.” While part of the reason for this is because two-wire traditionally performs better than standard systems in lightning strikes, benefits like wire savings and the ease of maintenance should not be overlooked.

As the use of this technology becomes even more widespread, a contractor who installs two-wire systems can consider himself to be on the technological cutting edge. And being on the cutting edge can help differentiate you from your competition. In other words, a contractor who installs two-wire can become number-one in his marketplace.
 
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