The Reliability Files

Thru-Panel Voltage Detection Makes Sense With NFPA 70E & CSA Z462

EP Editorial Staff | January 13, 2011


Workplace electrical safety has found its way into every facet of our electrical world. Maintenance departments struggle to keep equipment running while staying compliant with NFPA 70E/CSA Z462 standards.

As a result, they look for smarter, safer and more productive ways to keep machines operational. Enter thru-door voltage detection.

Keeping personnel away from live voltage is foundational to electrical safety. More important, electrical safety demands a precise answer to the question, “Is there voltage?” Thru-panel voltage detectors go a long way in providing the crucial first answer to this overarching question, while a voltmeter provides personnel with a second, redundant answer. Thru-door voltage detectors provide much needed “visibility” of voltage from outside the enclosure without exposing personnel to the hazard. Not surprisingly, companies using thru-panel voltage detection on their equipment have found this concept to be overwhelmingly embraced by all levels of maintenance and reliability professionals.

Here are two key benefits offered by thru-door voltage detection. More benefits can be found at


Increased Productivity and Safety with Mechanical LOTO…
Workers must isolate electrical energy when performing mechanical LOTO (lockout/tagout) procedures. Externally mounted voltage detectors provide a means of checking voltage inside an electrical panel safely—from outside the panel. Without them, a mechanic performing mechanical LOTO would be required to work in tandem with an electrician, who, using a voltmeter would physically verify voltage inside an electrical panel. In this case, the electrician is exposed to voltage. With thru-door voltage detectors, the mechanic can single-handedly check for zero electrical energy without any exposure to voltage.

Reduced Voltage Exposure and Arc Flash Risk with Electrical LOTO…
Voltage is the common denominator in an electrical accident or an arc flash. No voltage means no accident, no arc flash. Electricians performing electrical LOTO with an installed thru-panel voltage detector reduce their own risk because they are able to pre-check the internal voltage state without opening the enclosure. Next, they open the panel to replicate a zero energy reading with their voltmeter as per NFPA 70E 120.1.(5). Because of the lessened risk of voltage exposure with an installed thru-panel voltage detector, some conclude that once the panel is open, the need for personal protection equipment (PPE) is also reduced. Whether or not you agree with this, voltage detectors remain a low-cost, redundant voltage verification tool that reduces arc-flash risk, increases safety and enhances productivity—all for an installed cost of $150.

Return On Investment
Those who work in the automation world need electrical safety. NFPA 70E and CSA Z462 are vital elements in providing safe work environments. Before thru-door voltage checking, companies had to sacrifice productivity for the sake of safety. Now, by incorporating thru-panel voltage detectors, employees working on machines can do so with confidence.

Philip Allen is president of Grace Engineered Products. He believes increased electrical safety and productivity are natural byproducts when exposure to voltage is reduced or eliminated. For more information on thru-panel voltage detection, please visit

Grace Engineered Products
Davenport, IA

For more info, enter 260 at




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