Q&A: Switching Circuit Breakers
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Switching Circuit Breakers

Questions: Various people via e-mail
Answers by: Al Havens, Hugh Hoagland, Lee Hale
Date: February 2013

PPE Information on Switching Circuit Breakers

There are a lot of questions around the appropriate personal protective equipment (PPE) while switching circuit breakers.


Question:

I am curious about your opinion on a theoretical situation. Say, for example, I have a 277/480V, 400A panel which provides power to HID lighting fixtures. Assume that the upstream transformer is the service transformer for the building-it might be on the large side, say 2000kVA. The available bolted fault current might be pretty large (40k-45kA). Would you recommend PPE in this situation, and if so, how much?

Answer:

I am assuming someone performed an arc flash and shock hazard analysis and posted the arc flash incident energy, with other required information, on the panel. I would then evaluate the panel in terms of:

  1. How well has it been maintained? If screws are missing on the front cover, or the panel has its sides and front rusting away, or the panel is falling off its support, or the panel shroud covering the wiring has open blanks where circuit breakers would normally be, etc., then I would recommend that anyone operating any switch on this panel wear PPE that was equal to or greater than the incident energy stated on the panel's label.
  2. If the panel is relatively recent and it is well maintained with none of the conditions listed in items 1 and 2, and installed according to the NEC, there is not likely to be an arc flash hazard with this panel when operating the circuit breakers. Personnel may operate the switches with no PPE. However, my personal recommendation would be to wear clothing that at the least conforms to the 70E's less than or equal to 1.2cal/cm2 section of Annex H, table H.3(b).

Question:

Does it matter whether smaller breakers (say 20A) are switched individually or you are switching the 400A panel all at once?

Answer:

If the panel met the criteria of item 5) above, I would follow the recommendations in items 5) and 6). If I were switching the main 400A circuit breaker for the panel, I would dress up to the incident energy as listed on the label.


Question:

Q: An issue came up recently at a site where I'm working where the company contracted someone to perform an arc flash study. The contractors were observed in an electrical room without any special electrical PPE on and were opening the hinged cover of a panel to expose the operating switch portion of the circuit breakers (the main cover remained in place). My feeling is that this activity falls under "Opening Hinged Covers (to expose bare, energized electrical conductors and circuit parts)" in Table 130.7(C)(15)(a), p. 36, of the 2012 NFPA 70E. The contractors' opinion was that they were not involved in "electrical work" and therefore were not subject to the 70E standard. The argument is that as long as all of the knockouts are in place for the circuit breakers there may be little or no potential to contact bare, energized electrical conductors and circuit parts. However, I have seen many electrical panels in which the knockouts are missing or that cardboard or tape is covering the knockout locations.

Can you render an opinion from your experience as to what type of PPE the contractor should be wearing?

Answer:

I think your concern was well taken. If a person does not know that every knockout and circuit breaker space is covered with appropriate covers (cardboard and tape are not appropriate covers), when they open a hinged door, they may be opening a door that exposes energized circuit parts or conductors. The key issue here is "interacting with electrical equipment" which includes opening hinged doors.

As to what level of arc rated PPE to wear, if there is a label on the panel, I recommend wearing PPE that is equal to or greater than the rating or category listed on the label. If there is no label, I recommend wearing Category 2 or what is listed in NFPA 70E Table H.3(b), greater than 1.2 cal/cm2 and up to 12 cal/cm2.

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