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 Post subject: PPE Selection based on Generic Labels vs. Detailed Labels
PostPosted: Thu Sep 06, 2012 8:06 am 

Joined: Mon Oct 19, 2009 7:42 am
Posts: 30
Several years ago we applied generic arc flash labels on electrial equipment, down to disconnects, in all of our buildings. This was an interim step to comply with the NEC while we completed a formal arc flash analysis.

Our formal arc flash analysis is now complete and we are begining to replace generic labels with the new detailed labels that reflects the calculated incident energy. The scope of our analysis included all of our 120/208 volt panelboards but only included panelboard loads fed by molded case breakers 100 amp and larger and motors 50 Hp and larger. This seems typical for how far down I have seen others limit their analysis. Based on this scope, we still have equipment fed by branch circuits from the 120/208 volt panelboards (i.e. disconnects switches) with generic labels that were not included in the analysis. Typically, we use the NFPA 70E task tables for selecting PPE when there is a generic label on the device.

Based on the analysis, the calculated incident energy at the many of the panelboards is less than 1.2 cal/cm2, which allows us to utilize our standard electrical work clothes, equivalent to that required for HRC 0.

If possible, our workers like to avoid using PPE higher than their normal work clothes, which is understandable especially when it's hot. One of our qualified workers noted, "if I need to do voltage checks at a disconnect switch with a gereric arc flash label, and fed by a 120/208 volt panelboard, using the NFPA 70E tables I would need to use HRC 1 level PPE. If that panelboard has a calculated incident energy less than 1.2 cal/cm2, do I still need to use HRC1 level PPE or can I assume that the incident energy at the disconnect switch will also not be any higher than the incident energy at the panelboard, which then would allow me to revert to normal work clothes equivalent to HRC level 0?"

Anyone have any thoughts on how to answer this? Do we need to expand our analysis beyond our previous scope to eliminate these possible PPE inconsistancies?


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PostPosted: Thu Sep 06, 2012 7:39 pm 
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Joined: Mon Jan 18, 2010 11:35 am
Posts: 525
Location: Wisconsin
You should never assume that a downstream location always has a 'not higher than upstream' Arc Flash Incident Energy (AFIE) level. It is not unusual to find the added conductor impedance lowers the fault current enough that the protective device is slower to operate resulting in a higher AFIE.

IMHO, this rarely happens below 70A but sometimes happens above 200A.


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PostPosted: Mon Sep 10, 2012 8:06 pm 
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Joined: Wed Jun 04, 2008 9:17 am
Posts: 428
Location: Spartanburg, South Carolina
If you do not do a calculation of incident energy, and the equipment doesn't fall into the <240V, <125 kVA exception, then you have to use the task tables. You also have to assure that the fault current and clearing time limits of the task tables are met.

What was the basis of the "generic" labels? What PPE category is on the generic labels?


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PostPosted: Tue Sep 11, 2012 4:55 am 

Joined: Mon Oct 19, 2009 7:42 am
Posts: 30
The generic labels were an attempt to comply with the NEC requirements at the time and an intermediate step while conducting a formal arc hazard analysis. They were a basic arc flash and shock hazard warning label that directed one to the requirements of NFPA 70E and the HRC task tables. There were no PPE categories shown on the label.


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