The Simplification of Circuit Mapping

When performing any wiring retrofit, all electrical connections and wires need to be traced and properly identified. Electrical codes require connections to be properly labeled, but inevitably there are circuits that have been rewired sometime in the past, are not labeled or are improperly marked. Badly marked circuits not only pose a safety hazard but will delay construction. With retrofits, you are even more likely to run into wiring that predates current building code, so electrical contractors have to be prepared for the unexpected every time they start a new wiring job.

The only way to ensure regulatory compliance and construction safety is with a workable circuit mapping strategy.

The only way to ensure regulatory compliance and construction safety is with a workable circuit mapping strategy.

Depending on the scope of the job, it can take hundreds of man-hours manually tracking each wire to its circuit termination points. When you consider that in construction time really is money, the time wasted in man-hours tracing incorrectly or unmarked circuits adds up quickly and could impact your profits on the job. That’s why you need to have a circuit mapping and identification strategy ready before you begin.

Building Codes and Safety Concerns

Properly labeled wiring is essential for both regulatory compliance and installation safety.

For example, the National Electrical Code (NEC) and the Occupational Safety and Health Administration (OSHA) have clearly defined regulations regarding proper circuit labeling. OSHA 1910.335(b)(1) states, “Safety signs, safety symbols, or accident prevention tags shall be used where necessary to warn employees about electrical hazards which may endanger them … .” NEC 408.4 states, “Every circuit and circuit modification shall be legibly identified as to its clear, evident, and specific purpose or use.” Failure to properly label circuits, even in a building retrofit, could result in expensive fines. OSHA conducted 32,000 inspections in 2016 and found 1,424 electrical wiring violations at thousands of dollars per violation.

Mislabeled breakers in residential, industrial, and commercial buildings also pose a hazard to building management and emergency personnel. To make wiring safer, the NEC amended 408.4 in 2008 to require all panelboards to be labeled to indicate the source of the power supply to minimize the risk working on energized panelboards.

The only way to ensure regulatory compliance and construction safety is with a workable circuit mapping strategy; ideally one that doesn’t take a lot of time and manpower guessing or using outdated, inefficient techniques to identify electrical end points.

Options for Mapping Electrical Circuits

A circuit mapping receiver at a receptacle.

A circuit mapping receiver at a receptacle.


There are multiple ways to trace electrical circuits. The first step is to assess the existing wiring to see if the building already conforms to NEC standards. Do the panelboard circuit directories identify the existing circuits? If so, are the identifications verifiable and correct? How many circuit labels are missing or wrong? After you assess the current circuit labels, you have to test.

One testing methodology is the old trial-and-error method to trace circuit breakers and fuses: You throw the circuit breaker and identify the circuits that are affected. Of course, suddenly dropping the power load could create problems, such as damaging office equipment or shutting off vital systems. What you really need is a safe, fast and reliable way to define the circuit without dropping the load.

You can try the two-man methodology, where you test each circuit using probes at the end point. Of course, this means manually checking every circuit using a transmitter at each branch circuit and using a cell phone or radio to verify connections. It’s inefficient and time-consuming.

Then there is the challenge of creating a comprehensive circuit map of the structure. Most circuit-tracing devices only trace one circuit at a time. You still need to track those end points and gather that information into a wiring diagram.

PHOTOS: Tasco Inc.

About the Author

Steve McCasland
Steve McCasland is president of Tasco Inc., a manufacturer of electrical testing equipment.

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