LLB wrote:
Now we have a new Informational note No. 2 that states:
"normal operation of enclosed electrical equipment operating at 600 volts or less, that has been properly installed and maintained by qualified persons is not likely to expose the employee to an electrical hazard.
Does this mean operating a breaker or racking in / out a breaker on new equipment that has been tested and is in good / new condition is not a possible arc flash hazard? I think this new note just added to the confusion.
Opening/closing: Yes. And the installed/maintained part is very easy to answer. See the next major section which details specific detailed requirements for maintenance; specifically 70B and/or NETA MTS. Unfortunately in reality neither of these is very realistic either and needs work, but those are the only two general standards out there I'm aware of. For molded case circuit breakers the "bible" is NEMA AB4 which is available free from NEMA. IEEE Gold Book has extensive data on failure rates and cursory examination shows that with some careful consideration of possible failure modes, dangerous (arcing) failures are at least 10^-4 or 10^-5 or less under those circumstances, which is suffficiently low enough that most risk assessment procedures consider it acceptable risk.
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Doesn't this new note also contradict the on going debate about doors open vs. doors closed. i.e. operation of enclosed equipment... ...properly installed ..... not likely to expose to hazard... etc.
Not at all. It simply document's the 70E Technical Committee's position. The additional notes under the arc flash analysis section plus the section describing required maintenance together clearly indicate the position as to acceptable maintenance practices. Properly installed is pretty straightforward as well since that is described in the NFPA 70 section as well as the requirements in NFPA 70E (coordination, AIC/SCCR, etc.).
