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Irrigation industry analysts predict that within the next five years, two-wire control systems will be the industry standard for most mid- to large-sized residential and commercial installations in the U.S.
Rapid changes are already taking place and contractors, particularly on the East Coast and Midwest, are converting to two-wire installations for practical reasons:
Two-wire is not a new technology. Attempts to simplify wire runs were made in the 1960s and 70s, primarily for golf courses. However, those early installations used DC current and had a range of problems. In the last 10 years important technical improvements have been made to ensure reliability and to simplify installation and operation.
Two-wire systems have now been developed using AC current and advanced decoder/receiver technology. Two-wire irrigation has become the standard throughout Europe and in many areas of the developed world. In fact, decoder/receivers using Underhill 2-Wire technology have been utilized in more than 100,000 valve installations.
Switching to two-wire doesn?EUR??,,????'?????<
Two-wire controllers use just a single pair of wires that extend from the controller to each valve in the irrigation network. Instead of a maze of wires running to each station, there are just two wires going through the entire system, starting from the controller and running out to the last valve in the network. The two-wire path can be branched in any direction that works best on the site.
The time, effort, wire and other materials needed to install two-wire is considerably less than a conventional system. Just laying out the two-wire is a fairly simply process.
For example, with two-wire you set up the most direct path to the valves. Originating at the controller, you take the two wires ?EUR??,,????'?????<
Each valve decoder/receiver has its own unique address corresponding to the station number. During installation each valve decoder/receiver is programmed in the field with that specific address.
As the controller runs through the program, it sends out a signal, looking for a specific valve?EUR??,,????'?????<
This relay of information from the controller to the decoder/receivers is what makes two-wire technology different from conventional multi-wire systems.
Installing two-wire does not require any special equipment or tools. You can use the same valves that you are familiar with and the same solenoids and waterproof connectors that are on your truck. Even the wire is typical irrigation wire.
The only new components are the ICC decoder module (for the Hunter ICC) or a universal decoder module for all other controllers, along with the universal senders and decoder/receivers at each station.
Any existing commercial controller can easily be entirely (or partly) expanded or converted to two-wire. Let?EUR??,,????'?????< In a conventional installation, you would dig trenches to accommodate the wiring from the controller to the new valves, then extend the common and run a hot wire from each new valve back to the controller. There would be significant costs with labor, wire, valves and additional materials. By expanding with two-wire, you could either install a two-wire path from the controller or select and disconnect hot wires from any two valves and use these two wires to create a two-wire path to the controller without digging any new trenches or running more wire. This is particularly useful when the expanded area is across a parking lot or busy street. If you are expanding a system that was originally converted to two-wire, it?EUR??,,????'?????< Underhill?EUR??,,????'?????< Expanding Commercial Sites Two-wire also gives you the ability for easier system expansions and modifications. What if you need to run wire under a wall at a commercial site? What it a shopping center expands and adds new buildings, parking lots and landscaped areas? With two-wire the solutions are seamless. You can run a small conduit sleeve under the wall pavement with just two wires instead of a large conventional bundle of multi-wire. If you need to add zones at a commercial center, just locate the most convenient two wires and hook in from there. Or go to the last valve in the network and add as many extra stations as necessary (up to 63). You never have to dig in new wire back to the controller.
In a conventional installation, you would dig trenches to accommodate the wiring from the controller to the new valves, then extend the common and run a hot wire from each new valve back to the controller. There would be significant costs with labor, wire, valves and additional materials.
By expanding with two-wire, you could either install a two-wire path from the controller or select and disconnect hot wires from any two valves and use these two wires to create a two-wire path to the controller without digging any new trenches or running more wire. This is particularly useful when the expanded area is across a parking lot or busy street.
If you are expanding a system that was originally converted to two-wire, it?EUR??,,????'?????<
Two-wire also gives you the ability for easier system expansions and modifications. What if you need to run wire under a wall at a commercial site? What it a shopping center expands and adds new buildings, parking lots and landscaped areas?
With two-wire the solutions are seamless. You can run a small conduit sleeve under the wall pavement with just two wires instead of a large conventional bundle of multi-wire. If you need to add zones at a commercial center, just locate the most convenient two wires and hook in from there. Or go to the last valve in the network and add as many extra stations as necessary (up to 63). You never have to dig in new wire back to the controller.
Some contractors prefer to set up an irrigation system in which one decoder/receiver operates two valve stations. In that case, up to 96 valves can be controlled by one 48-station ICC with two decoders per station.
The difference in the amount of wire used in a two-wire system can be substantial. While less wire means less labor (and less trouble if repair work is required), it also means less cost. Some contractors report saving 80 to 90 percent of wire cost and labor when they converted to two-wire.
Installing a two-wire system is uncomplicated and cost effective, especially when a job requires 300 feet of mainline or more. Savings on copper wire is a major advantage, but system expandability and simplified trouble shooting also add up to cost savings.
Most breaks are due to damage caused by trenchers cutting the two-wire path or a poorly tightened wire nut. Let?EUR??,,????'?????< This means that part of the system would be inoperable, starting where the break occurred. If the wires were cut between Valve Station #10 and Station #11, for example, all valves beyond Station #11 would cease operating. Repairing a two-wire path is very easy compared to multi-wire. There are only two wires to reconnect and most decoder systems do not care which way the wires are reconnected. If it is not obvious where there is a break in the two-wire path, use a volt meter to check the voltage about half-way down the path. If there is power at this point, it is obvious the break is in the direction at the end of the two-wire path. Next check the voltage again half-way toward that end of the two-wire path, and then half-way again until the break is found. This series of voltage checks normally takes only a short time.
This means that part of the system would be inoperable, starting where the break occurred. If the wires were cut between Valve Station #10 and Station #11, for example, all valves beyond Station #11 would cease operating.
Repairing a two-wire path is very easy compared to multi-wire. There are only two wires to reconnect and most decoder systems do not care which way the wires are reconnected.
If it is not obvious where there is a break in the two-wire path, use a volt meter to check the voltage about half-way down the path. If there is power at this point, it is obvious the break is in the direction at the end of the two-wire path. Next check the voltage again half-way toward that end of the two-wire path, and then half-way again until the break is found. This series of voltage checks normally takes only a short time.
Using a proven technique which differs from most other decoder systems, grounding is not required along a two-wire path. However, it is recommended that the decoder module is grounded in the controller. Many two-wire decoder modules and decoder/receivers have two-year warranties that include lighting protection, even with direct hits.
Two-wire systems generally offer greater resistance to lightning damage because there is less copper wire in the ground to attract lightning strikes.
Two-wire systems are often utilized during a ?EUR??,,????'?????< The future of two-wire is only going to grow. Contractors who have switched to two-wire have discovered the valuable savings. With the cost of copper wire and labor rising every year, the question is: Can you afford not to be competitive with two-wire? Ed Underhill has worked in the landscape irrigation industry for more than 20 years and is president of Underhill International Corp. in Lake Forest, Calif. The company manufactures two-wire control systems, large turf rotors, FCI Profile nozzles and a range of water-saving equipment for sports fields, golf courses and commercial installations. Additional information about two-wire products and installations is available at www.underhill.us.
The future of two-wire is only going to grow. Contractors who have switched to two-wire have discovered the valuable savings. With the cost of copper wire and labor rising every year, the question is: Can you afford not to be competitive with two-wire?
Ed Underhill has worked in the landscape irrigation industry for more than 20 years and is president of Underhill International Corp. in Lake Forest, Calif. The company manufactures two-wire control systems, large turf rotors, FCI Profile nozzles and a range of water-saving equipment for sports fields, golf courses and commercial installations.
Additional information about two-wire products and installations is available at www.underhill.us.
Francisco Uviña, University of New Mexico
Hardscape Oasis in Litchfield Park
Ash Nochian, Ph.D. Landscape Architect
November 12th, 2025
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