IRRIGATION: Two-Timing

Scott Fay prides himself on keeping up with everything new and innovative in the irrigation industry. So it was only natural for the president of Treasure Coast Irrigation and Landscape in Hobe Sound, Fla., to embrace two-wire irrigation when it was introduced in the late 1980s. “As soon as it was available on the market, we started learning it and installing it,” he says. “Our mission statement identifies us as a go-to company for irrigation, so it’s our goal to master every segment of irrigation technology.”
 
Two-wire irrigation is one of the fastest-growing segments of the irrigation industry, says Bernie Malonson, product manager, Rain Bird, Tucson, Ariz. Benefits like simplified installation and lower installation costs make it an economical alternative to traditional irrigation. Like with any new product, it takes time and training to properly install two-wire irrigation. “Two-wire systems require a little more care during the installation process, but after contractors have done it once or twice they love it,” says Malonson. “It just takes a little tweaking of the standard processes – like being in Europe and driving on the left-hand side of the road.”

WHAT IS TWO-WIRE? In a nutshell, a two-wire irrigation system does the job of a standard irrigation system using only two wires. The two-wire path runs from the system’s controller to each control valve located throughout a job site. A decoder is installed at each valve and programmed with its own unique address, or station number, to which the controller sends operational commands. The two-wire path carries the power and the data necessary for the controller to communicate with each decoder. When the controller operates, it sends signals to the decoders that turn the valves on and off. “It’s like an Internet system where everyone is running on a network,” Malonson says. “Each valve has an address, and rather than running a separate wire out to everything, two wires are spliced and connected to each valve.”
 
Two-wire systems are most often installed on sites with 20 valves or more, but they can just as easily run systems with as few as three valves. However, experts agree two-wire irrigation is most cost effective on larger jobs. While decoders can be costly – $100 to $300 each depending on brand and size – money saved on less wire can add up, especially when working on large jobs. “Sometimes two-wire is cheaper to install and sometimes it’s more expensive,” Fay says. “You can save money on wire, but you add the cost of the decoders.”
 
Installation price depends on the system’s size and the job site’s layout and conditions, Fay says. “If you have a small system that has to run a long way, a two-wire system would be more cost effective,” he explains. “But if you have a system with a lot of valves, the decoders add up.”
 
Fay prices his two-wire installations similarly to his traditional irrigation installations, and considers the costs of material, labor, overhead and expenses, then factors in site conditions and desired profit. Most of Fay’s two-wire clients are large commercial properties with more than 30 valves, and two-wire installations make up 15 percent of his company’s business.

THE GOOD AND BAD. Unlike traditional irrigation systems, two-wire systems offer contractors flexibility. “With two-wire, the main line and the wire can be laid out early in the project, and zones can be added whenever they need to be,” Fay says. “If the architect wants to change the design and add things like annual beds that require different amounts of water, that’s not a problem. With traditional systems, you have to know all of that ahead of time, but with two-wire, you’re all set.”
 
Malonson agrees. “In a perfect world, contractors think each site through as much as possible before installing an irrigation system, but things come up,” he says. “If a housing development buys an adjacent piece of land and wants to irrigate it, a contractor simply needs to splice and add valves.” As a result, the decision to install two-wire irrigation usually depends on a property’s plans for future growth, Fay says. “Some clients, like commercial sites, plan to add on in a year or two so it makes sense to install a two-wire system,” he says.
 
To add one or more valves, contractors simply splice the wires at the specified area and connect the valve. This splice-and-connect method drastically reduces the necessary amount of wire and is also less labor intensive. “If you have a football field and want to install a sprinkler every 10 yards, a traditional system would require thousands of feet of wire,” Malonson says. “With a two-wire system, you’d run two wires up the middle of the field and splice it off every 10 yards. It definitely speeds up the installation process.”
 
However, when it comes to maintenance, two-wire irrigation can slow things down. Because the systems run on just two wires, tracking them once they’re installed can be a more technical process, Fay says. In a traditional irrigation system, a “hot wire” and a common wire run from the clock to every valve. With a two-wire system, every valve shares the same wire, making the wires and decoders more susceptible to damage. “With a two-wire system, every valve shares the same wire and, if done incorrectly, wire tracking can burn out a decoder,” he explains.
 
Programming information for each decoder on a system also can be a difficult task, especially for non-English-speaking laborers. Employee training is the only solution to this problem, Fay says, so he added a two-wire component to his company’s 32-step irrigation training system, through which his employees participate in comprehensive hands-on and classroom training. The two-wire section takes about three hours and teaches his crews everything they need to know about installing and maintaining these systems.
 
Two-wire irrigation systems are also more susceptible to lightning damage than traditional systems, and Fay suggests contractors follow manufacturer recommendations for lightning protection, such as implementing surge and short-circuit protection features. Quality wire connectors are also important when installing two-wire systems. “A two-wire system is only as good as its connections,” he says. “That is not a place installers should cut corners.

“Two-wire systems carry more voltage than standard 24-volt irrigation systems,” Fay continues. “They operate in milliamps, which makes the wire path more sensitive to resistance and wetness. The more resistance there is in the wire path, the better chance of line-path or decoder failure.” Any open or exposed wire in a splice can shut down multiple zones to a site, Fay says, adding this happens more often when contractors use “cheap” connectors, which are easily exposed to water and dirt. Quality connectors cost about three times more than inexpensive options.

TWO-WIRE FUTURE. Already a standard method in Europe, Fay predicts the popularity of two-wire irrigation will continue to grow in the coming years, and attributes much of this growth to improvements in equipment. “All of the major irrigation equipment manufacturers have come up with good answers to two-wire systems,” he says.
 
Participating in industry events and associations also helps contractors learn the ins and outs of two-wire. Most of Fay’s knowledge of new irrigation products and techniques – like two-wire – comes from his yearly pilgrimage to the Irrigation Association’s International Irrigation Show. “I’m a big believer that contractors who want to stay up on new trends need to be there,” he says.
 
Like any new product, contractor acceptance will fuel the future growth of two-wire irrigation. “When two-wire irrigation first appeared on the market there were a lot of contractors who rejected it because it was different, nontraditional,” Fay says. “Installing and maintaining two-wire became a competitive advantage for us because we were able to offer our clients the newest thing.”