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 Post subject: Which label to print? (ETAP 7.5.2)
PostPosted: Thu Mar 01, 2012 6:34 am 

Joined: Thu Mar 01, 2012 6:30 am
Posts: 6
Im using ETAP 7.5.2... and I have run a few arc flash studies before... still trying to learn as I go along... as I guess its evolving over time...

I just want to be clear on which labels I should print and for what?

Let's say I have a simple layout... Utility source.. to some MCC... to breaker (HMCP) in MCC bucket to a starter to a feeder to a bus to a switch (unfused) then to a pump.

Now ETAP brings up 2 labels... one for the bus thats like Cat 0... and 1 for the breaker which is Cat 4... which label should i put on that specific MCC bucket?

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PostPosted: Fri Mar 02, 2012 7:35 am 
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Location: Connecticut
NFPA70E-2012 has the requirements for labels. Article 130.5 (C), Page 125. I always use the highest cat level when modeling MCC's which is usually the main lug compartment. Unless the MCC line up had bus bar isolation, flash over can happen. Etap 11 has a new feature that allows PD isolation or no isolation. It then looks at the next upstream PD and uses the clearing time to calcualte IE. Etap's label templates can be modified to suit your need.

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PostPosted: Mon Mar 19, 2012 10:23 am 

Joined: Tue Jan 10, 2012 6:11 am
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I do not have much experience with ETAP. But following can give an idea.

Generally an arcflash label denotes the immediate protective device on the line side. (in event of coordination - which acts first on a particular fault). So basically it represents the arc flash energy level released at the device you are operating till the above breaker/relay trips.

In your case, if I assume there is a incomer breaker for the MCC, the label to be pasted on MCC bucket should indicate the case if a fault happens on line side of the breaker or on the bus, and the energy released till the MCC incomer breaker trips.

So if there is no tripping device between your bus and the MCC breaker, both should have same label. (ignoring bus impedance)

I'm not sure what your cat-4 label is for. It could be for the switch on the downstream for which breaker in MCC bucket acts as tripping device. and if so, MCC bucket should have the cat-0 label (for this either MCC incomer should have been the tripping device).

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PostPosted: Mon Apr 16, 2012 7:32 am 
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Joined: Thu Oct 18, 2007 7:10 pm
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Location: NW USA
Not exactly certain of your situation but it seems like the breaker is protecting the bus, and therefor the bus calculates as a lower arc flash exposure.

If the breaker is in a separate enclosure (detached) from the bus you could put the higher exposure label on the breaker and the lower exposure label on the MCC. If the breaker is part of the MCC our practice has been to label the entire MCC as the higher HRC as technically that energy level is available within that structure.

IF the main breaker is within a segregated section of the MCC, you could label that section with the higher exposure and the other sections with the lower HRC, however; their is a slight risk that could confuse folks.

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