Tracer wire is crucial to protecting workers from accidentally disturbing underground utilities, but how do you know what type and size wire is necessary for the job?

Depending on where you are, tracer wire may be spec’d into the general work plans. This means the wire’s gauge and type have already been pre-determined, so there isn’t much wiggle room. In other cases, the project may specify that locator wire must be used but stops short of dictating specifics.

Signals Aren’t an Issue

If you’ve worked with locator wire, you know its purpose is to find underground utilities. However, the process is slightly more complex than that.

To find the wire, a transmitter sends a signal through the tracer wire, which travels through the copper or copper clad steel (CCS) conductor and is picked up by a receiver to trace it. Though some jobs may opt for larger gauge wire during installation, it doesn’t do anything to help the tracer wire signal.

The truth is that when it comes to signals and size, it doesn’t really matter. The signal doesn’t change based on wire size.

Conductivity vs. Signal

When people talk about tracer wire, you might hear something about either conductivity or signal. The two terms are independent of each other, though they both play a role in how the wire performs while doing its job.

Conductivity measures a material’s ability to pass current and depends on gauge size and material.  The larger the wire, the more current it can safely carry without damage. Current is typically associated with electrical applications.

Signals are associated with utility locating and are created when an electrical or electromagnetic current is sent by a transmitter through the cable. They are produced as current passes through the wire, then picked up by a receiver. In the case of tracer wire, the signal is a low AM frequency similar to your car radio.

Strength Impacts Selection

If you’re buying tracer wire for strength, such as copper clad steel, then size and construction 100% matter. Locator wire comes in sizes from #18 AWG to #8 AWG, and as the gauge size increases, so does the break load. Construction of the wire also matters – copper clad steel is stronger than copper conductor and also has a higher break load. Break load, also known as tensile strength, is a term used to describe the force needed to break the line.

In situations where the wire is being laid alongside conduit, pipes, or cabling, a #14 AWG copper conductor works well. For pipe bursting, where a high break load is needed, a #10 AWG stranded copper clad steel cable might be the way to go due to its massive 4,700-pound break load.

Compounds and Flexibility Matter

When choosing the wire you need, know what application it’s used for and the conditions it will live in. Unlike the gauge of the wire, the compounds used in its construction have a greater impact on things like conductivity and general use case.

There are two types of general tracer wire insulations – both fall under the polyethylene (PE) or High Molecular Weight Polyethylene (HMWPE) family. Within the PE or HMWPE family there are two different types of plastics or compounds – depending on the application, one is generally more suitable for use than the other.

Let’s say you have an open-cut situation where the wire will be installed manually. You would likely want an LLDPE solution because the wire is softer and more flexible than HDPE. This is because the polymer chain used to create LLDPE insulation is less rigid, allowing it to flex and move.

Flexibility does have its limitations, though. Directional drilling or pipe bursting jobs require HDPE insulation because of its rigidity, strength, and abrasion resistance.

Although gauge size can impact flexibility, conductor composition also plays a role. Copper conductors are more flexible than copper clad steel ones, but copper only comes in soft or hard (annealed). Copper clad steel is less flexible but has a better variety of options available that can help offset some of the lost flexibility, especially in larger gauges.

And just in case you thought about cutting corners on your project by using THHN wire, Henry Elwyn, National Water and Sewer Sales Leader for Kris-Tech, advises against it.

“NEVER use THHN in place of tracer wire,” Elwyn explained. “THHN is an electrical wire that is not direct burial rated. Unlike tracer wire, THHN uses nylon insulation that isn’t heavy-duty and doesn’t stand up well to underground applications. As a result, the wire’s insulation will likely crack after installation, resulting in eventual damage to the copper conductor and a lost signal.”

Choose Based on Application, Not Size

At the end of the day, gauge size matters – just not in the way you think it does.

Gauge size matters when you need the wire to not break during a critical pipe burst process or horizontal directional drilling operation.

If you’re concerned about not being able to locate your tracer wire, Elwyn says to keep a few things in mind while planning your project:

  • #12 AWG tracer wire is the most common for open-cut installations, but larger gauges may be necessary for more intensive projects
  • Make sure you choose insulation applicable to the environment (LLDPE is designed for maneuverability, and HDPE is meant for abrasion and crush strength)
  • Don’t use THHN as a tracer wire

Not sure what type of locator wire to use for your next underground utility project? Kris-Tech’s team of experts can walk you through the process.

Contact our Tracer Wire team to explore your options and learn how Kris-Tech can make your next installation as smooth as possible. And don’t forget to subscribe to our newsletter!