Circuit mapping is a relatively new strategy that eliminates the need to manually trace end-to-end connections. Instead, the circuit mapping tool uses a transmitter that connects to the panel and sends a signal to each branch circuit. The receiver uses digital signal processing and displays each corresponding circuit by number, even if there isn’t a direct electrical contact, and it works on energized and de-energized circuits. This makes it easier to identify which circuit is connected to each transmitter lead.
The beauty of circuit mapping technology is that it can create an accurate circuit map without disrupting the power, which can be especially valuable when wiring a medical center, data center or some other building where consistent power is critical.
Circuit mapping also saves time and money. Field studies estimate the time required to trace circuits can by reduced six-fold using circuit mapping. If you assume that labor costs average $38 per hour, you could be looking at substantial savings.
Circuit Mapping Best Practices
Once you have your circuit map, it’s important to follow best practices to ensure circuit labels are compliant and useful in the future—when someone else needs to rewire the building.
Labels are required for wires, cables and circuit breakers, as well as Arc Flash and Safety labels. Cables, for example, need to be identified with permanently affixed identification labels. Labels are usually heat-shrink tubes, vinyl wire wraps, flag labels. The labels themselves should meet UL969 specifications for legibility, defacement and adhesion.
The colors required for cable labels are spelled out in ANSI Z535. NEC 408.4(A) also states that every circuit in the panel has to be clearly identified and distinguishable from other circuits in the panel. The panel wiring also should be marked with color-coded labels (NEC210.5(C)(3)) with documentation identifying each color. Of course, all labels need to be rugged, smudge proof and resist fading. The ANSI/ITI 606-B standard provides guidelines for proper identifications of individual and bundled telecommunications wire and cables, faceplates, patch panels, cabinets, racks and other wiring.
With all the additional wiring in today’s buildings for telecommunications, networks, building automation and other applications, cable management can be particularly challenging. NEC standards are only designed to meet safety requirements so you have to go beyond the NEC code to properly identify wiring. For electrical wiring, NEC 408.4(A) prohibits labeling of circuits that describe transient conditions of occupancy, such as “John’s office”. Because of this, consider creating a naming and numbering system that follows a logical hierarchy.
Once the wiring is labeled and complete, it needs to be tested and fully documented. Create a legend that matches the wire labeling convention and be sure to describe the wiring in sufficient detail to accommodate future upgrades; troubleshooting; and moves, adds and changes (MACs).
If there was a common cable identification standard that all would adhere to, the job would be easy. However, standards change, and installers have their own quirks and methodologies. With any electrical retrofit, you inherit the wiring system of the original builder or the previous contractor. Your goal should be to clean up past mistakes and leave a clearly labeled wiring system that is easy to maintain and upgrade. To do it efficiently, start with the circuit mapping tools that simplify wire tracing and create a wire labeling convention that is easy to follow and document.
PHOTOS: Tasco Inc.