NFPA 70E
NFPA 70E
(OP)
I would like to know if the various codes affecting arc flash studies require each and every live electrical panel at a site to be considered.
I work at a federal aviation lab center. Thousands of panels exit here. Some "experts" here are of the opinion that existing power panels are "grandfathered" in.
An arc flash study would not be a trivial undertaking.
Thank you.
I work at a federal aviation lab center. Thousands of panels exit here. Some "experts" here are of the opinion that existing power panels are "grandfathered" in.
An arc flash study would not be a trivial undertaking.
Thank you.






RE: NFPA 70E
OSHA is approaching thru the General Duty clause which states that a place of employment must be free of recognized hazards and arc flash is a recognized hazard. If the hazard can not be eliminated, then the employee must be protected. OSHA is in the process of revising Subpart S to address arc flash using NFPA 70E. In fact, the forward to NFPA 70E states that it is primarily written for OSHA.
Ok, the legal stuff out of the way, on to practical matters. You do not have to do every panel. What I have done is to go as far as 480V power panels and MCC's. For lower voltages, I use the PPE tables in NFPA 70E. Another approach would be to calculate arc flash until you reach a level where below that it is Category 0.
RE: NFPA 70E
Another reference is IEEE-1584 which covers calculation of arc-flash energy. Per this standards, 208/120V systems smaller than 125 kvA do not require calculation because there is very little chance of an arcing fault occuring. Of course, shock hazards obviously still exist. IEEE-1584 does require calculation of arc-flash energy for all 240V (and higher) systems.
As wbd states, the NFPA 70E is different than the NEC - it does not have the force of law through adoption by states and cities. However, OSHA does consider NFPA 70E a "consensus standard". So if you're not in compliance with NFPA 70E, you'll need your own comparable saftey plan or a good reason you're not following it.
RE: NFPA 70E
RE: NFPA 70E
The advantage of doing a study is to find the portions of the system that have enormously high arc-flash energy potential so the appropriate safety precautions can be taken.