Two-Wire to the Future

Two-wire irrigation technology has existed since the 1970’s in various forms and was initially used on golf courses. The basic concept of a two-wire controller is the irrigation controller uses a single two-wire path to communicate to a decoder or output device and uses the same wire to provide power to each zone valve through the solenoid.  

A traditional controller requires a dedicated wire between the controller and each zone valve connected to the controller.  Each valve must be linked through a common wire that runs back to the controller. This is a reliable and tested method of installing an irrigation system; however, there are several reasons you might consider a two-wire system for your next install: 

• Traditional controller systems can use a lot of wire. As a dedicated wire and common wire are required for each zone or control valve, this can quickly add up, especially in larger systems. A two-wire system can use up to 70% less wire than traditional systems depending on coverage area.  This could mean lower installation and material costs for the same design and performance. 
   
• Long wire runs can be achieved with a two-wire system.  If you’re designing or installing a system that has zone valves a significant distance from the controller, rather than upsizing the station wire to a larger gauge, a two-wire system may be a better option.  Some manufactures can have wire runs of more than 1.5 miles with 14-gauge wire and 6.5 mile runs if you loop the wire.  
   
• Two-wire systems can often communicate back and forth with the decoder or output device with real time operating and diagnostic information. Imagine, rather than spending hours looking for and troubleshooting a cut wire, the controller could identify the damage and direct you to a specific location on the wire path. 
   
• Other than the controller, two-wire systems are fully below ground systems.  This has several benefits including allowing the site to remain undisturbed with no above ground enclosures which can also limit vandalism risk. As everything “downstream” from the controller is below ground, this also limits the risk of water damage.  All the downstream, below-ground components are weatherproof and can be direct buried without worrying about damage. This can be especially useful if the system is being installed in a flood-prone area.
   
• Two-wire systems are very easy to expand.  Rather than having to install a “home run” wire from the new zone valve back to the controller, a two-wire system only requires a connection from the existing two-wire path to add new zone valves (assuming there is capacity in the controller.)

There are some areas to watch out for if you are installing your first two-wire system.  Since two-wire systems may have longer wire runs, the wire path needs to be protected from lightning induced surges. Each manufacturer has a unique specification on the grounding requirements for installation.  In addition to the grounding requirements, the wire splices need to be carefully installed on a two-wire system using direct bury connectors to the manufacturer’s specifications. Since the system is sending both power and communication on the same wire, poor connections can have a detrimental impact on the system operation.  In addition, as two-wire systems are completely below ground, a good installation drawing or “as-built drawing” is essential to maintain the system in the future. 

Two-wire technology continues to improve, and irrigation manufacturers are launching new products in the two-wire market each year. As a result, two-wire systems are becoming more price competitive and are a viable option for many projects from smaller residential installations through large commercial designs.

SiteOne has the knowledge and products to support you as you explore two-wire installations. This category is expected to grow as technology improves; give yourself a competitive edge by learning two-wire irrigation installation now.