How do you label arc-resistant switchgear? Table 130.7(C)(9) shows Cat 0 for operations with the doors closed, but if you've done an IE analysis, you're not supposed to use Table 130.7(C)(9). The IE analysis does not consider whether or not the switchgear is arc-resistant.

If you calculate an IE of 5 cal/cm², do you need Cat 2* or 5 cal/cm² rated PPE to operate a breaker or is Cat 0 adequate?

Good question, we all know once you do the analysis that is your hazard level and you are not supposed to revert back to a lower HRC from the tables, bu tin this case that makes no sense.

I still think the equipment needs a label with the Ei for other operations but for operating the gear with the enclosures bolted up in this case a HRC 0 makes sense. Interested to see other ideas on this one.

That's a great one! I don't think there is an offical answer / interpretation like so many other things. However, I'm thinking along Zog's line of reasoning. Label the equipment because there could still be live exposed work at some point - voltage testing or whatever.

Racking and operation would be the proverbial "interaction" with doors closed which is a bit of a judgement call and in this case the "Arc-Resistant" classification would enter into the call.

Document the rationale in your policy and label it HRC 0. Its another undefined nuance subject to interpretation. Just document your method and keep it consistent.

Thanks for the replies. I think I'll recommend Cat 0 for closed door operations and use the calculated IE for open door operations. In this MV metal-clad switchgear, you have to open a door to get to the draw-out breaker. The manufacturer states:

The breaker compartment doesn't have high-voltage components, but I'm inclined to treat racking the breaker as not protected by the arc-resistant design and use the calculated IE for this operation. Other operations with the breaker compartment door open should be OK with Cat 0, however. What do you think? There are controls, meters, and relays mounted on the breaker compartment door. Another possibility would be to limit Cat 0 operations to those with the breaker in disconnected or fully withdrawn position so that working on the controls can't result in a breaker operation while energized.

I met with the VP of a large switchgear company many years ago when arc resistant switchgear was begining to make inroads into design. He gave me the the "cooks tour" of their facility and showed me their MV Switchgear design.

It was specifically designed so you could rack in using Category 0 PPE which was the whole point of the equipment. I think I would ask your supplier about your specific situation to see if they can give you better clarification. It seems odd you would have arc rated gear that you can not rack in without dressing up to arc rated protection based on the Ei.

You are correct however, when in doubt, be conservative - in this case use the calculated Ei until you know for sure.

Arc rated gear that does not allow for closed door racking? That makes no sense.

OK Zog, you can say it in fewer words than me

I took jghrist's comment to mean that you have open the door to remove, draw-out, the breaker from the cubicle, not necessarily to rack-out the breaker from the stabs. I would agree with Zog and Brainfiller that you have totally defeated the purpose of havging the expense associated with arc-rated gear if you have to open the enclosure to perform racking tasks.

OK, that makes sense. So the question becomes would opening a door on MV switchgear with no exposed live parts (Besides control voltages) due to the shutters and pulling a breaker from the disconnected or removed position out to the floor be considered an "interaction" that may produce an arc flash hazard.

At our facility we do not concider that as an interaction. However, before we open the breaker cubicle the techs go around to back of the gear, remove the covers, check for voltage and apply grounds (while in appropriate PEE). Once that is done they remove their PPE and then proceed to remove the breaker from the cubicle.

You are correct, the breaker must be opened and racked to the disconnect/test position before opening the door. At this point, any arcing that could occur would be in a separate compartment from the breaker compartment.

Category 0 should be adequate even in the breaker compartment.

I would agree, but I wonder how OSHA would interpret that. I think we need a poll!!

The bigger problem I see with the standards and Arc resistant switch gear is the type of gear specified and the working distance that it is tested to. based upon the IEEE c37.20.7 there are two potential working distances, 1 meter or 3 meter, similair to the IEC. in many cases the actual work activity will be well within that distance (or front of panel since that is where the test is measured from). what is the PPE level within that distance??????? how does one calculate that PPE level at a closer distance. the only assumption I think could be done without testing is to then calculate without the arc resistant credit.

To the point about doors open when racking, all gear is different. the first that needs to be identified is to which method/rating or arc resistant gear is being procured? take a look at the different types within IEEE C37.20.7. not all are the same. We learned this lesson on a China Project with the basic of basic IEC AR gear. the same item applies to their products.

Look you're supposed to do a hazard analysis even with the 2012 edition of 70E. Anyone who has done one knows that you can't just blindly use whatever results that a software program spits out. There are always issues with differences in actual working distances, recognition of when the upstream value applies such as in panelboards and when it doesn't, and so forth. Another example is when equipment is known to be in poor maintenance condition at which point 70E clearly states that any assumptions about whether or not a breaker trips go out the window. None of these can be done in a vacuum. For the same reasons with some kinds of equipment, such as arc resistant switchgear, equipment design and configuration also must be considered.

In summary, you can't just do arc flash hazard analysis, let alone risk analysis, in a vacuum. It is critical to know and understand equipment design to do it correctly.

That being said, there are some complications. Many manufacturers are selling arc resistant low voltage gear. All they are doing is subjecting the equipment to the same test regimine as the ANSI test for medium voltage switchgear. So, is it "arc resistant", or not? I would say it might be, provided that I can see documentation on how it was tested and certified.

The second complication is that the gear only protects against switching operations with the doors closed and latched. This is nice but the poor maintenance worker that still has to undo all the fasteners to open the gear, and receives ZERO additional benefit, is also the very same one that is most likely to be injured. Adding arc resistance adds about 10 to 25% to the price. And it goes after the tasks which are least likely to cause an injury in the first place. I would much rather consider adding high resistance grounding, arc flash relays, maintenance switches, bus differential protection, and so forth. These add between 0 and 25% to the cost but the major difference is that they improve the safety of the equipment for ALL tasks and workers.

I re-read the thread starter and noticed this:


NFPA 70E-2012 removed Cat 2* from the PPE requirements.

Not quite. Category 2 disappeared and 2* remains as what we now call "2". The old standard allowed for some situations where face protection was not needed and others where it is.

Yes, thank you for the clarification as I was not clear in stating that there is a Category 2 in NFPA 70E but rather was trying to highlight that there is no Category 2* in the current version of NFPA 70E