Circuit Tracers: More Than Meets the Eye

Circuit Tracers: More Than Meets the Eye

The classic application for the circuit tracer involves finding which breaker supplies a given 120V load (Photo above). But circuit tracers aren't limited to 120V circuits or simply finding breakers. These devices can also locate neutrals, ground lines, branch circuits, feeders, control wiring, and more. What's a common Code violation that makes your job tougher and more costly to perform? Hint: The

The classic application for the circuit tracer involves finding which breaker supplies a given 120V load (Photo below). But circuit tracers aren't limited to 120V circuits or simply finding breakers. These devices can also locate neutrals, ground lines, branch circuits, feeders, control wiring, and more.

What's a common Code violation that makes your job tougher and more costly to perform? Hint: The same one makes your job more dangerous and more likely to interrupt customer operations. Does the phrase “circuit directory” come to mind? In 110.22, the NEC states, “Each disconnecting means shall be legibly marked to indicate its purpose.”

How many times have you wished someone would've filled out that panelboard circuit directory so you didn't have to go through the process of flipping breakers? In an ideal world, every panelboard would carry a reasonable description of each circuit. And every facility would have up-to-date drawings to verify that directory — rather than disagree with it. But in an ideal world, electrical contractors would make 50% margins on every job and customers would roll out red carpets as your truck pulled up.

The reality is you need a safe, quick, and dependable way to identify the breaker that defines a given circuit — without dropping the load. This is where the circuit tracer has earned its stripes.

But because these devices are so useful for identifying breakers and fuses, many electricians simply haven't looked beyond that to the many other uses for these devices. By not using the full capability of thse devices, you may be letting increased profits and additional revenue pass you by.

More than a breaker finder. There's nothing complex or mystical about using a circuit tracer. Typically, you can use one right out of the box. The simplest circuit tracer arrangement consists of two components. You plug a sending unit into a receptacle and run a detection probe over individual breakers until you find the right one. A circuit tracing kit may include additional accessories, such as a signal generator that you clip into a circuit — this is useful for devices that are hard-wired (vs. devices that plug in). Of course, certain cautions apply (“Circuit Tracer Safety” below).

What possible uses can you have for this instrument other than determining which breaker supplies a given device? Consider these possibilities.

Tracing wires. How many times have you tried to follow wiring by visually tracing the raceway it's in? It's not easy, is it? Using a circuit tracer, you can eliminate this time-consuming, error-prone approach. Wire tracing is more useful than you may think. And don't forget: you can trace wires in walls, ceilings, raceways, cable trays, and other locations — even underground.

Locating insulation leakage. Your customer's network is down, due to signal loss in a major cable. You could repair this and quickly restore the system if you could identify where the insulation is damaged. But how do you locate the insulation leakage?

You could send someone to your home office to find the one TDR your company owns. And then call in Joe — who knows how to use the TDR — from a job 30 miles away so he can find the short. But that extra wait will most likely make your customer unhappy.

It's much faster to use a circuit tracer to pinpoint where a cable has a leakage to ground (high or low resistance). To do this, you will probably need a power source other than the transmitter that comes with the unit. The manual for your particular unit should tell you how to do this. You could, for example, use half a dozen 9V batteries to get 54V for this purpose. For power cables, a 54V insulation test is insufficient — use an instrument suitable to the task (e.g., a megohmmeter).

Locating shorts to ground. A breaker trips and the facilities manager tells you it won't reset. If that breaker supplies the feeder for the three 400-hp motors that run the plant air compressors, you don't have long before production starts screaming. So how do you find the fault?

You could try “sectionalizing” the feeder wiring. To do this, you divide the wires into successively smaller sections to isolate the fault. But this is a time-consuming method that potentially requires a great deal of cutting and splicing. Other techniques work better if you have the expertise and the equipment to perform them.

But if you have a properly rated circuit tracer, you can quickly pinpoint the fault. You clip on your transmitter at the breaker, per the instructions in the manual (this may require you to take power from an adjacent, energized breaker). Then you walk the raceway down with the detector until the signal disappears and you find the ground fault location.

Locating dead circuits. Suppose a customer asks you to remove unused cabling from a plenum. Your crew heads out there with customer drawings and rips out all of the unused wires and cables. Just as your foreman is telling you how great things are going, the customer is frantically calling your cell phone because their new 10GB Ethernet network has just failed. You look at your drawings. There's no 10GB Ethernet there. What is the customer talking about? That's exactly the problem. Documentation and actual installation can differ dramatically — and often do.

But if you use your circuit tracer, you can mark up the customer's drawings to show the actual wiring. While such a documentation upgrade will help you do your job, it could also be valuable to the customer, so you could offer it as an upsell. But be sure to consider selling this work before you actually do it.

As with any test instrument, the circuit tracer has its limitations. But it also has advantages that can allow you to make better use of constricted resources such as troubleshooting capacity and labor hours (“The River Walk Case Study” below). That means not only more potential revenue, but higher profits as well.

Lamendola is an electrical consultant, writer, and proprietor of Codebookcity.

Sidebar: Circuit Tracer Safety

Circuit tracers come in a variety of ratings. And, like DMMs, they come in a variety of quality levels. Don't use a cheap DIY version for your industrial or commercial work — it simply lacks the safety features a professional quality unit offers. A DIY homeowner may want to trace down two or three circuits, and then stick the instrument in a toolbox to be forgotten. On the other hand, you may need to check hundreds of circuits in a Class III location. The extra money you fork over for a unit of suitable quality will keep you safe. The bottom line is make sure the unit you're using is rated for the voltage at which you'll be working.

Sidebar: The River Walk Case Study

Like the Alamo, the River Walk is a popular attraction in San Antonio. First electrified in the ‘60s, the site recently developed serious maintenance issues. Part of the process of resolving those issues was documenting 40 years of undocumented changes amid dozens of electrical panels in many locations. Many of the wires were buried, some went under the river, and some ran along the bottoms of the bridges.

The city brought in Central Electric, a local electrical contracting company, to trace all circuit paths and bring their drawings up to date. Co-owner Chris Martinez personally oversaw the project, and to ensure its success, he assigned 23-year veteran Steve Mitchell.

Initially, Mitchell and apprentice David Garcia used the “flip the breaker” method and a pair of radios. This quickly proved to be inefficient — and, in some cases, futile. Based on previous experience with circuit tracers, Martinez and Garcia knew they needed instrumentation they didn't have. Martinez contacted a manufacturer for guidance. Intrigued by the implications for their ongoing R&D efforts, the manufacturer sent four people — including the product manager and an R&D engineer — to the site, along with new test equipment.

Mitchell and Garcia had already documented the location of each outlet and traced half of them back to their respective breakers. Armed with the new test equipment, they quickly traced each of the remaining outlets back to its panel and breaker.

But then they found some breakers had no known loads associated with them. So they worked backward from these breakers, walking the wires down with a large circuit tracer. Some fed streetlights and other loads that didn't fit the electrical schematic, complicating maintenance. They even discovered that one panel was fed from a source at a remote site.

But as well as this worked, you don't always need a circuit tracer. For example, Mitchell and Garcia were able to map out half of the circuits in just a few days using their original technique. But those were the easy ones. Using the circuit tracers, they mapped out the “impossible” half in one day.

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