All Posts By

Dave Rewitzer, PE

Data Center Miscoordination: A Case Study

By Conduit

The NEC requires over current protective devices (OCPD) to protect cables from overheating and catching fire which is achieved using long-time (LT) breaker settings. The NEC also provides guidance on ground fault (GF) and ground fault delay (GFD) settings. Additional settings on OCPDs include long-time delay (LTD), short-time (SD), short-time delay (STD), and instantaneous (I), which can be adjusted and coordinated to protect personnel and equipment from dangerous fault currents. If the only goal was…

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Green Eggs and Blam!

By Conduit

Prior to the 2018 version, NFPA 70E simply cautioned that “greater emphasis may be necessary with respect to de-energizing” equipment with incident energy (IE) exceeding 40 cal/cm2, “when exposed to electrical hazards.” This nebulous direction was applied within the industry by simply labeling everything over 40 cals as “Dangerous – No PPE Exists.” In its new 2018 version, NFPA 70E eliminated this cautionary language. This may lead some to infer that working on energized equipment…

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