Today's irrigation controllers have become extremely sophisticated,  incorporating computer technology to improve timing and diagnostics.  However, as advanced as the technology becomes, you cannot escape  the necessity to connect the controller to each and every valve  with a bundle of dedicated wire.

And that can turn into a lot of wire. Unless you are installing  valves on a small, regularly shaped piece of land, you can literally  have miles of buried wire. Worse yet, the arrangement of these  wires is usually a disorganized web spread out throughout the  site.

A contributor to this problem is the nature of conventional controllers,  which typically have dedicated wires that connect to each valve  they control. Each controller is equipped with a terminal strip  that has one common wire and one hot wire for each valve. These  hot wires—up to 42 of them (and even more on a few heavy-duty  models), are run out to the individual valves. The common wire,  on the other hand, runs from valve to valve, throughout the array.  In a large installation, there could be well over a mile or so  of wire going to a single valve.

From this . . ......... ....... ..... . .To This

The Short History of 2-Wire
The first attempt to reduce wire was from Paul Cordua, president  of HIT Products, Inc., with a 4-wire system. It consisted of  two wires to carry the power and two wires to carry the signal.  This was in 1966 for agricultural installations.

Perhaps the first attempt to start the 2-wire revolution was  made in about 1975. "It was introduced as the greatest thing  since sliced bread," says George Cook, vice president of  marketing, HIT Products in Lindsay, CA one of the manufacturers  of 2-wire technology in the U.S. The 1975 version of the 2-wire  controller used completely different technology than today's.  This was the Binar system, introduced by Johns Manville. The  system used D/C latching solenoids, a different form of communication  over the 2-wire path. The Binar system had technical problems  and was eventually pulled from the market.

About 12 years ago, an irrigation contractor in Sweden, frustrated  with conventional controllers, partnered with a Danish electronics  firm to develop a more efficient system. They developed a 2-wire  system which has since been successfully marketed worldwide.

Most installations have been in the golf course markets with  over 1500 installations.
HIT Products, Inc. spearheaded 2-wire technology for the commercial  and residential markets and is a leader in the field. They recognized  the potential of 2-wire and developed the Logic 1, a 42-station  controller that uses standard 24-volt A/C valve solenoids, standard  wire and no special connectors.

The Danish company anxious to market a commercial product in  the U.S. was approached by Larry Sarver, who was a golf distributor  and an irrigation contractor. Sarver presented them with a business  plan and for the last three years has been working to develop  Tucor, Inc.
Sarver, with his Danish partners, took the 2-wire technology  used in the golf market and created a line of products aimed  at the commercial and residential markets.

The Story of the Standard Controller
brickclosedThis abundance of wire in conventional controller installations  cause a variety of problems. One of them becomes painfully apparent  when you have an accident with the wire.

Say, for instance that you install an irrigation system and have  a whole network – a spider web – of wire, buried in  the ground. Finally, the time comes to plant the first of a group  of trees. The workers come in with a backhoe and the equipment  makes a nice big hole, perfect for the tree. When the shovel  rises from the hole, looking a lot like a dirty pasta fork, there  hanging from the shovel is a large clump of wires and it's obvious  that half of them are broken!

brickopenThis is one of the worst nightmares for a contractor. Before  any other planting is done, someone must repair each wire. That  requires figuring out which wire goes with which wire, and connecting  them. On sophisticated installations, the wires are color-coded-up  to 42 different color combinations (first find the red-green  stripe with the white circle on it, etc.). However, after two  years underground, those colored wires become all the same color.  The nightmare grows even bigger when you realize you must test  each one.

Recently, another option has come on to the irrigation scene,  which can, among other things, vanquish the prospect of the above  nightmare. Two-wire controllers feature a pair of wires that  run from the controller out to a valve, then from that valve  to the next, and so on. Instead of a web of wires going from  the controller to its valves, two wires travel from the origin,  at the controller, to the last valve in the chain.

Time, Headaches and Money
As you might imagine, the effort to hook up a 2-wire system  is much less than a conventional system. The planning alone becomes  a rather common-sense process.

In the 2-wire world, you take the most direct path to your valves.  Start at the controller and take the wires – a common wire  and a hot wire – to valve #1, then run the same wires from  #1 to #2, and so on, until you reach your last one.

Another nice feature is that the 2-wire technology does not require  using special equipment. The valves are the same as in any other  installation and the wire is the standard irrigation variety  (perhaps a slight bit larger gauge than in a conventional installation).  The waterproof connectors are standard, as are the irrigation  valve solenoids.

Other than the controller, the only special component is the  connector to the valve, called a receiver, that identifies it  as valve #1, #2, #3, etc. Since the price of the controller and  valves in the Hit Products 2-wire system work out to be about  even with conventional controllers, the only difference ends  up being the wire.

This communication technology from the controller to the receivers  makes the 2-wire process different from conventional controller  technology. In HIT's 2-wire system, the controller applies 24  volts to the entire path of wires. The valve stations, each containing  a receiver, have their own unique address.

The controller sends a signal with a sort of telephone number,  in search of a particular valve. If the first receiver has that  telephone number, it closes the switch and allows the 24 volts  to pass through to activate the solenoid.

Tucor has a patented conversion terminal strip, so that existing  conventional systems can be converted to 2-wire. When you add  decoders – Tucor's communication link between the controller  and the valve – in the field, the existing wire path (the  one that contains a multitude of wires) is transformed into a  2-wire system. Once you turn the system on, a communication network  bridges the new and existing system. You may start from any valve  in the existing system and add as many new valves as that controller  will allow.

"Lets say I've got an old landscape," postulates Sarver, "and I want to  put flowerbeds in...but I don't have enough valves and wires.  I can convert it to Tucor's 2-wire system, put Tucor's controller  in place and then I can add as many valves there as I want, without  having to add wire."

Cook says the difference in the amount of wire used can be huge.  "Every job is different, of course, but you can save 80  to 90% of the wire cost and the labor by using the 2-wire system."
Less wire could also mean less trouble. Contractors are often  responsible for the operation and maintenance of every bit of  wire in an installation, and a conventional system can contain  more than 15,000 feet of wire buried in the ground. two-wire  technology significantly reduces this liability, simply by reducing  the amount of wire.

The Logic 1 is the only 2-wire model that HIT currently makes,  but more are in development. Cook says, "We believe in 2-wire  technology. It truly is the technology that will be used as the  standard in the future. It's so easy, it's so straightforward,  it's so cost effective. It is the future! The bigger the job,  the more desirable 2-wire is, because of the scope, the amount  of wire going out to a site."

Sarver is very confident about the future of 2-wire technology.  "Within four to five years," he says, "this will  be the way things are done." Cook agrees, saying that 2-wire  will soon be the standard of the industry, "because there's  every benefit and, quite honestly, no drawback." Cook comments,  "it took fax machines about five years to catch on in this  industry, computers and e-mail are coming along at a much faster  pace. Two-wire systems will be commonplace in the very near future."

Irrigation Goes Hi-Tech
Tucor had an idea to add a modem (a device used on computers  to communicate over telephone lines) to its controller. The Tucor  controller comes with the software that allows you to call up  that controller from anywhere in the world, and turn it on and  off. And for a bit more investment, you can even buy a software  management package that allows you to monitor multiple controllers.

"We were doing a job in Phoenix," remembers Sarver,  "that we couldn't get a phone line to. So, we came in with  cellular phones. We were actually calling the cellular equipment  attached to our controllers – located in the Pittsburgh  office, but we were using a Phoenix cellphone system...and calling  it from Denmark! So, the call went from Denmark to Phoenix, through the  cell network, and through the switched cellular system, all the  way to Pittsburgh, where we remotely operated the controllers."

outside1openHIT's later models will accommodate more stations and have more  outputs at the controller. "You might want to put the controller  in the middle of your site and go out in two directions,"  says Cook. "We'll also have one in a heavy-duty housing,  with pedestal capability."

Conventional controllers will probably continue to dominate the  irrigation landscape, for the short term. The very fact that  almost all current installations have conventional technology  will maintain the status quo for a while. But, the contractor  looking at that backhoe full of broken wires is likely to wonder  whether there's a better way. He may well have found it.

Let's take another look at the backhoe scenario, described  earlier. If the pair of wires is cut somewhere in a 2-wire arrangement,  the whole system would be disabled, following after the point  of the break (if the break occurred between valves #12 and #13,  valves #13 and higher would cease to operate). Would the conventional  controller system not fare as well, or better, than the 2-wire,  since there are individual wires going out to each valve?

Nope. This is because the conventional uses a common wire, which  is connected to every valve, anyway. Once the common wire is  broken, the signal is cut for all remaining valves.
However, the larger issue is, if the common wire is severed in  the conventional system, you'll have a big job finding it. The  advantage of 2-wire in this scenario is that the controller is  able to locate the approximate point of the break. You would  know, for example, that the break is between valves #12 and #13.  You would then need a ground fault detector to pinpoint the exact  point of the break, but you'd have a specific reference point  between those two valves.
Cook maintains that the bigger factor is labor and troubleshooting.  "Let's say they have one plant and they accidentally dig  up 15 wires. It can take hours to repair – if you're really  good. With 2-wires you simply re-connect the two wires and you're  back in business."

The ability to expand and modify your valve configuration is  another big advantage of 2-wire, says Cook. "In a given  job, you may have to run the wires in a sleeve under a road or  other concrete structure. What's cool about this is that you  would just have to have a sleeve that would accommodate two wires  instead of a typical bundle of wires."

"But, let's say there's a change in design and all of a  sudden your customer wants to add some zones. You're using 30  zones and you want to add five," describes Cook. "You'd  have to pull these wires all the way from the controller location  through these sleeves and get out to where the valves are going  to be (and typically, they're the most remote valves). That's  a challenge to have to do."

With the 2-wire system, you need only find the closest two wires  and just tap in from there. Or you can go to the last valve and  add as many as you like (up to 42).