NFPA 70 E Table 130.7(c)(9) (a) question

[zog]

Arc flash PPE requirements and boundaries apply when interacting with switchgear, no mention of exposed live parts. All arc flash analysis assume the door or panel will fly open.

The shock protection boundaries (LAB, RAB,PAB) apply when there are exposed live parts.

 

[WDeanN]

I was answering WdeanN who had posted in post #9 that they had already done an analysis but were debating their internal policy of treating "exposed energized parts" differently from nonexposed. . The subject was no longer the arc flash calculation but rather determining the logic or illogic of their policy. . My conclusion was:

?All that stuff makes a difference when a blast occurs.?

David,
The point that I was getting at was when to require wearing AF PPE. In general, we require it when changing the state of a switch or breaker, or when there are exposed, energized parts.

I am personally against applying this to single phase tasks, however. Although the 277 breaker may be in a 480V 3 phase panel (which will be posted) the likely hood of an INDIVIDUAL single phase arc flash event is minimal, and can not be calculated using the current 1584 methods. (Yes, if it is in a panel which has the energy posted, they will be required to dress out to change the state of any breaker in the panel.)

I use the 1584 equations to calculate the energy levels. I do not like using a mixed approach of applying the 70E tables for some equipment, but requiring full PPE for calculated and posted equipment.

 

[coulter]

zog -

Arc flash PPE requirements and boundaries apply when interacting with switchgear, no mention of exposed live parts. ...

I'm not finding this in 70E or 1584. If fact:
70E Article 100 - Definitions:
"Flash protection boundary. An approach limit at a distance from exposed live parts within which a person could receive a second degree burn if an electrical arc flash were to occur."

...All arc flash analysis assume the door or panel will fly open. ...

I will need some help here. I couldn't find anything on this in 70E or 1584.

All of the models are for open air, or a three sided box. Now does that mean the bolted cover blew off or the work was being performed with the dead front off or open? I can't tell. 70E, Table 130.7.C.9.a certainly appears to lend belief that the covers will remain in place. For the equipment the OP is discussing, 480/277 lighting panelboards:
CB operation with covers on is Haz Cat 0
CB operation with covers off is Haz Cat 1

I did check UL 67 on panelboards and as you said, the hinged cover can open, but only up to 60 degrees. And as jim said, the shell can't be distorted such that live parts are exposed.

I got to wonder, if arc fault calcs assume that a bolted dead front is going to be blown off a panel, what use is the PPE when that missle is stuck in one's head?

I suspect I am missing something. Do you have any additional references I could read?

carl

 

[ron]

On a slight diversion, arc resistant SWGR is wonderful, as long as the doors are closed. I understand that if the doors are opened, it performs the same as regular SWGR during and arc fault.

 

[zog]

Coulter,

Look at the 70E handbook for discussions of the doors assumed to fly open. The 2008 70E ROP's has several discussions about doors and the "interaction with switchgear".

you are right about it not being clear in the 70E or 1584, I happen to know several members of these commitees and I get to have discussions several times a year on these topics. Both of your questions are commonly asked questions in my seminars.