Installing two-wire irrigation systems
|By Mary Elizabeth Williams-Villano|
You can achieve installation two-wire installation without trepidation.
Some people like tradition, finding it comforting and safe. Other more iconoclastic types buck tradition wherever possible. Which way do you sway? The answer may reveal your risk tolerance level and also your position on two-wire irrigation systems.
Contractors who are used to installing conventional irrigation systems can be a bit intimidated by two-wire and its mysterious decoders. “The reason a lot of people are still afraid of two-wire is because they think it’s new,” says Mark Grenert, vice president of Tucor Inc., Wexford, Pennsylvania.
But two-wire is hardly new. It’s been around more than 20 years and has become the go-to system for large commercial sites. Still, two-wire may be new to you and to a lot of other contractors who have mainly installed conventional irrigation systems.
“Contractors that have only worked on conventional who suddenly inherit a two-wire can definitely be afraid of it,” says Grenert. “They think it’s so intimidating, so technology-dense that they don’t even want to pursue it.”
You can’t blame a guy for sticking with what he knows. That strategy may not work forever, however, because two-wire is making inroads into the residential irrigation space.
There are other reasons why some contractors shy away from two-wire. “Cost is one,” says Dave Shoup, senior product manager, central control systems for Hunter Industries, San Marcos, California. “The price of entry has been high. Not many contractors do projects large enough to justify it. Two-wire as a straight-up alternative to conventional wire has traditionally only made sense or allowed a contractor to break even at a certain system size.”
But contractors do like the flexibility of being able to add stations at will without trenching back to a controller or running a bundle of wires.
The big trick with a decoder-based system, says Shoup, is that it depends on a really good installation. “What happened when two-wire first came out is some guys just sort of jumped in. They’d been wiring sprinklers the same way for 25 years, so they didn’t necessarily pay attention to the stricter requirements, and they got burned. Mystery problems on a new installation? Nobody wants that.”
It’s like the first time you tried sushi. If it gave you a tummy ache, it was probably the last time, too. When our initial experience with something is poor, it’s human nature to walk away and never look back. But a lot changes in 20 years. You aren’t using the same computer you used back in 1999, are you?
Two-wire systems are either easier to install than conventional systems or harder, depending on whom you talk to. Which part of the installation you’re talking about also makes a difference.
A conventional system has a wire going out to each valve plus a common. Every valve has the hot wire plus a common wire going back to the controller. For a 24-zone system, there’d be 24 wires plus a common for every zone.
In a two-wire system, the two wires coming out of the controller are hooked up to a decoder placed at the first valve. These same two wires are then connected to the next decoder and valve combination, and the next and the next. As you can see, much less wire is needed.
“What’s the best thing about two-wire systems?” asks Grenert. “There are only two wires. What’s the worst thing about two-wire systems? There are only two wires. All that data has to come down the same two wires.” That makes the installation simpler but at the same time, more exacting.
Keith Schweiger, CID, CLIA, CIC, CIT, CLWM, lands on the “easier” side of the debate. Now a key account manager at SiteOne Landscape Supply in Englewood, Colorado, he spent many years prior to that installing both conventional and two-wire irrigation systems.
“Two-wire is easier for a couple reasons,” he says. “Most of the work is trenched, so the wire can go right into the ground. You don’t need to know today exactly how many zones you’re going to need to run tomorrow. With a conventional system, you need to know that, because you have to install individual wires for all of them.”
Two-wire has more flexibility to adapt to changing conditions. “The fact that I only have two wires to make my connections is, to me, one of the best things about two-wire systems,” adds Schweiger.
But they are a tad touchy. Like millennials, two-wire systems are very sensitive.
“The copper wire has to be pristine, like jewelry; it can’t have any dirt on it,” says Mark Twiss, irrigation manager/contractor at D.W. Burr Landscape and Design Inc., Sinsbury, Connecticut. “Even a tiny nick in a wire can cause havoc.”
A conventional system is a lot more forgiving. It can handle a bit of sloppiness in installation, where a two-wire system really can’t. A higher level of craftsmanship is needed.
Quick facts about two-wire
• Always use the manufacturer’s specified wire and connectors.
• Give it some slack — leave extra wire at each t-splice and in the valve box for future servicing and to allow for ground and frost heave.
• Decoders are either AC or DC, and AC and DC solenoids may not be mixed within a controller installation. A decoder system will be either AC or DC latching.
• Ground the system with copper rods every 500 feet and at the end.
• Put the decoders inside the valve boxes and out of the elements.
You’ve heard the expression, “When all else fails, read the instructions?” That’s never truer than it is with two-wire.
“First and foremost, the most important thing is that you follow the manufacturer’s specifications — that’s critical, and they’ll differ with every manufacturer,” says Grenert. “Some require a certain kind of wire versus others. When there are problems, it’s often because you have someone installing a two-wire system the way he’s always been comfortable.”Twiss points out that before two-wire systems, installers used 14-gauge single-strand wire for everything. “Everybody used it and it didn’t matter whose clock it was on. That’s not the case with two-wire. The manufacturer’s specs apply to using the proper wire, the proper connectors and the right installation technique to connect everything.”
By “the right technique,” Twiss means that every manufacturer stresses the need to make sure the wire connections are done properly. “In the old days you would strip your wires, grease them together and put them in the DBYs, and for the most part they worked pretty well,” he says. “The old mechanical rotary 24-to-30-volt systems, you flipped a switch and they either worked or they didn’t. They were very stout and reliable. You could get away with mistakes and the fault could literally take years to show up.”
“But in two-wire decoder-based systems, the wire carries communications signals as well as power, so all of the wire connections have to be done both securely and properly.”
There’s another consequence to not following the manufacturer’s specs. For instance, Tucor wants you to use its own brand of double-jacketed tin-coated copper wire on its two-wire systems. “Just a little side note — if they don’t use our wire, there’s no warranty,” warns Grenert, “and the same is true of every manufacturer.”
Another reason to follow the maker’s specs to the letter — should you need another one — is that everything isn’t completely uniform across all brands. “In the real world there is some intermingling of wire,” Schweiger says. “It doesn’t mean that a system will fail, necessarily. But you’ll have much greater success if you follow the manufacturer’s requirements. A lot of guys found out the hard way that they needed to pay a little bit more attention to the specs.”
As was true for the wire, the same goes for the connectors, sometimes called splices, the little devices that link the solenoids to the system’s wires. The exact ones they want you to use will be specified, too, usually 600-volt-rated waterproof DBRY-6 connectors, with exactly the right kind of waterproofing gel inside, and they’ll come with instructions. “You do need to use the manufacturer’s recommended connectors,” says Schweiger.
Bad connections will create a host of problems. Sometimes they’ll show up quickly and sometimes not for a while. But they will show up.
Other problems are caused by failing to think inside the box. “Anything connected to the two-wire path must be installed inside the valve box, including the decoders,” Grenert stresses. “If they’re left outside, they’re exposed to weather.”
Ground the heck out of it
Grounding is especially vital with two-wire. It won’t keep lightning from striking a system, but if it should get hit, proper grounding will minimize any damage.
Some systems require separate grounding decoders in every valve box; others connect directly to the rods.
“We’ll ground the system right away at the point of connection with a 10-foot rod inserted into the ground 8 feet deep and put a surge protector and decoder on it,” says Twiss. “About 11 feet away from there, we’ll insert a grounding plate approximately 30 inches down. Then we’ll insert more grounding rods every 500 feet or so and another at the end of the line. That creates a kind of grounding umbrella that will protect the system.”
The rods and plate are installed in line with the main decoder wire. Should Zeus throw a lightning bolt at the ground, the surge would be confined to one section between two grounding circuits, meaning that you’d lose two decoders instead of 200.
Back to that pesky valve box — installers have differing opinions as to whether you need to place a grounding rod inside the valve box itself. Again, the safest course is to do what the manufacturer recommends. “Mark Grenert has always told us to do that, so I follow his point of view,” says Twiss.
Pros and cons
A 200-zone conventional system uses lots of wire, and copper isn’t cheap. With less wire used, you save both time and labor.
But one of the reasons two-wire has mainly been used in commercial and some high-end residential applications is its higher cost. Each decoder costs around $150, so whatever you saved on wire can be spent on buying decoders. You’ll also need copper rods and grounding plates. And two-wire controllers tend to be heavier duty and more expensive.
Two-wire has the edge when it comes to retrofitting. You have virtually unlimited flexibility to expand a system, anywhere you want, with no spare wires to run. “If a customer says, ‘I’d like to add two zones over here,’ it’s very easy to do that because you just add another couple of decoders to that wire, as long as your controller’s not full,” says Lyle Oulette, CIC, director of irrigation at Landscape Maintenance Services, Hillsborough, New Jersey.
Troubleshooting is less troublesome, too. “Using cable TV as an analogy, if half the block has its cable out, the problem isn’t at every single house,” says Schweiger. “It’s likely to be one connection, and when that is fixed, all six subscribers will be back up and running.”
Do they save water?
Twiss thinks so. “I have a 65-acre HOA community with multiple points of connection. We put in an ET- (evapotranspiration) based two-wire system, and it saved the community 6.7 million gallons of water valued at $28,000 to $30,000.”
There’s clearly money to be made installing two-wire systems. They open the door to bidding on big commercial projects with high profit potential. But before you venture into this world, “get some training, and have your guys get training as well,” advises Oulette.
Trodding the two-wire path may not be a simple journey, but it can be a road well worth traveling.The author is senior editor of Irrigation & Green Industry magazine and can be reached at email@example.com.
Simpler, cheaper, less fussy two-wire
Hunter Industries, San Marcos, California, has launched a new two-wire irrigation product called EZDS for “easy decoder system.” “It’s a cost-effective two-wire system that isn’t fussy, doesn’t require special anything,” says Dave Shoup, senior product manager, central control systems.
EZDS’ main points of difference include:
• no specified wire
• no specified connectors
• polarity no longer matters
• works on 24 volts
• no special grounding required
• no special power meter required
Shoup says Hunter developed EZDS in response to a frequent contractor request. “They’ve been saying, ‘I have existing wiring already in the ground from a conventional system. I’d like to use that wire to convert the system over to two-wire.’ Now they can.”
The EZDS system will work with the Hunter ICC2 controller and the Hydrowise HCC commercial controller, a Wi-Fi cloud-based control system that it shares a chassis with.
Intended for smaller commercial and high-end residential applications, the new system will accommodate up to 54 stations maximum. “We’re clearly not aiming at mega-giant commercial sites with this product,” says Shoup. “The idea is to broaden the base of the two-wire user pyramid. It opens up a whole new category of installations where a contractor may never have considered using two-wire before.”
There are only two pieces, an output module and a new single-station decoder that is placed one per valve.
No special wire or connectors are specified, but it is suggested that only direct burial-rated wire be used. The gauge of the wire will determine how far you can go with it. “You can use 18-gauge wire that’s left over for up to 900 feet in each direction; 14-gauge wire will get you to about 2,300 feet,” Shoup says.
While the connectors are no longer specified either, installers are urged to use professional-grade waterproof ones.
Another big difference is that no inline surge protection grounding is required. But if you work in a lighting-prone area like Florida, it’s advisable to add a surge arrestor.
The EZDM Output Module currently lists at $299 and the EZ1 decoders at $85 each. “It’s a significant price breakthrough for a name-brand decoder system, and it means the break-even point for two-wire just got way lower,” says Shoup.
Shoup says the EZDS system is not intended to supplant the existing two-wire systems sold by Hunter and other manufacturers, but to provide a lower-cost alternative for sites where two-wire had previously not been cost-effective or feasible.