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Does your facility or your client’s facility have circuit breakers rated 1200 Amp or higher?
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 Post subject: 240.87 Arc Energy Reduction - 2014 National Electrical Code
PostPosted: Sun Jan 26, 2014 8:20 am 
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There was a pretty significant change to the 2014 edition of the National Electrical Code Section 240.87 Arc Energy Reduction. Although the overall concept is similar to the 2011 version, 2011 addressed circuit breakers where there was no instantaneous trip. 2014 has expanded the requirement for ALL circuit breakers 1200 Amps and greater. The primary concern is the possibility of long device clearing times that can lead to larger incident energy levels during an arc flash.

This section now states:


240.87 Arc Energy Reduction. Where the highest continuous current trip setting for which the actual overcurrent device installed in a circuit breaker is rated or can be adjusted is 1200 A or higher, 240.87(A) and (B) shall apply.

(A) Documentation. Documentation shall be available to those authorized to design install, operate, or inspect the installation as to the location of the circuit breaker(s).

(B) Method to Reduce Clearing Time. One of the following or approved equivalent means shall be provided:

(1) Zone-selective interlocking
(2) Differential relaying
(3) Energy-reducing maintenance switching with local status indicator
(4) Energy-reducing active arc flash mitigating system
(5) An approved equivalent means

Here is this week’s question:

Does your facility or your client’s facility have circuit breakers rated (or adjustable) 1200 Amp or higher?
  • Yes
  • No

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PostPosted: Mon Jan 27, 2014 7:54 am 
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Some additional background - -

Some electrical inspectors had trouble enforcing 240.87 in the 2011 code because they typically are not trained to identify when a breaker is or isn't equipped with an instantaneous element. Their request was to modify the code so that an inspector could easily determine if 240.87 applied to a particular breaker.

Under the 2011 code there was also some discussion of what to do with a breaker that is equipped with an instantanous function that could be turned to an OFF position. The statements by the code making panel in the 2014 first draft and second draft reports indicate that having an instantaneous feature but turning it off is not acceptable.

Now a follow-up question - -

If a facility has a LV breaker rated 1200A or higher that is equipped with an instanateous trip feature that is turned on, but none of the methods (1) through (5) above are employed, is the breaker in compliance with 240.87 in the 2014 code?


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PostPosted: Mon Jan 27, 2014 8:26 am 
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jdsmith wrote:
Now a follow-up question - -

If a facility has a LV breaker rated 1200A or higher that is equipped with an instanateous trip feature that is turned on, but none of the methods (1) through (5) above are employed, is the breaker in compliance with 240.87 in the 2014 code?


That is exactly my question - which lead to this post. Thanks for picking up on it quickly.

My interpretation is this new language applies to all breakers 1200 A and higher regardless of whether an instantaneous trip is available.

I took this as using similar logic found in the ground fault requirement for 480Y/277 breakers greater than 1000 A. i.e. looking at a time current curve, there is a large range of currents between the long time pickup - LTP (1200A in this case - 1000A for ground fault) and the instantaneous - IP which can be upwards of 10 times the LTP.

That could be upwards of 12,000 A for 1200 A breakers and even higher for larger breakers before the breaker trips to limit the arc flash duration. There is normally a long time delay in the region between the LTP and IP. For ground fault protection, this was deemed a problem that required GF protection and now it seems the same logic may be applying for arc flash. It seems this area of the breaker's Time Current Curve / operating characteristic is the concern.

Now come the needed exceptions for 2017. If a breaker with a maintenance switch is upstream from a breaker 1200 A or larger (i.e. perhaps a large main breaker), does that upstream breaker with the switch qualify for reducing the arc flash energy of the downstream breaker that are larger than 1200A?

Just my thoughts - feel free to pile on.

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PostPosted: Mon Jan 27, 2014 10:51 am 
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Wow...somehow I missed this in the 2011 Code cycle, and it's pretty significant for what I do. Not that it matters...given the relatively cheap cost I've almost gone to de facto putting in resistance grounding from 1000 A and larger even for 480 V, so additional relaying is very low cost once you have a breaker with a shunt trip.

Even reading the Handbook edition, item #4 has me a big perplexed as to what it is referring to. What is intended by "active arc flash mitigating system"? I can think of several that might be what is intended but it's not clear:
1. Current limiting devices (backup fuses or current limiting breakers).
2. Equipment that meets the "arc resistant switchgear" rating, realizing that these days a lot of equipment is being rated under the ANSI standard even though it does not fall under that standard.
3. Arc flash relays, both the photoreceptive kind and high dI/dt relays.
4. Arc "quenchers"...high speed switches that purposely cause a bolted fault.

Depending on what is meant by "active" it seems like only #4 is what is intended.


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PostPosted: Mon Jan 27, 2014 4:28 pm 
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If you or your client's facility has a 1200 A or higher breaker, it was likely installed under a prior version of the code. Since the NEC is for installation rather than maintenance, the question seems irrelevant for the grandfathered breaker. The relevant question would be regarding plans to add 1200 A or higher breakers.


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PostPosted: Tue Jan 28, 2014 8:44 am 
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stevenal wrote:
If you or your client's facility has a 1200 A or higher breaker, it was likely installed under a prior version of the code. Since the NEC is for installation rather than maintenance, the question seems irrelevant for the grandfathered breaker. The relevant question would be regarding plans to add 1200 A or higher breakers.

The good news is you are quite correct about grandfathering. (Thank goodness) Could you imagine if everything became retroactive in the NEC?

The reason I worded the question like I did is most people would not have any future plans for new additions. I thought asking it this way would help gauge the magnitude of just how common 1200 A breakers are and shine a very bright spot light on the potential future impact of this revised NEC article. (and raise an eyebrow or two about a possible future exception as mentioned in my second post)

Thanks for the comment!

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PostPosted: Tue Jan 28, 2014 11:19 am 
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During the public input stage for the 2014 NEC there was at least one commenter that proposed the instantaneous element be present and set below the arcing current. This would have substantial implications - essentially forcing anyone who installed a 1200A or larger breaker to have an arc flash study performed, although the study could be limited in scope to just the buses immediately downstream of the 1200A or larger breakers.

I tend to agree that there is a big hole here where folks could be forced to implement protection schemes that offer little value since they already have instantaneous elements in the large breaker. Perhaps we could go out on a limb and state that the majority of breakers 1200A and above have instantaneous elements.

Like many "young" code requirements, 240.87 will take a few more code cycles to iron out so that
1) it meets the original objective of the code making panel
2) can be objectively inspected and enforced
3) is technically clean and coherent.

For anyone attending the Electrical Safety Workshop next week, several members of Code Making Panel 10 will be in attendance, as well as several other folks that are very knowledgeable about this 240.87 issue.

For any IEEE members:
The IEEE has a formal process for collecting comments and suggestions for changes to NFPA standards, formulating an IEEE position on an issue, then representing that position on the NFPA code making panels. For additional information on how you can participate in this process feel free to PM me.


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PostPosted: Wed Jan 29, 2014 3:30 pm 

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I'm wondering which manufacturer(s) got this wording changed. I understood if the breaker had no instantaneous but ALL breakers 1200A and above? REALLY??? :mad:

It reminds me of arc fault breakers that were foretold for the 2002 code back in the 1999 edition. They requirement was going to be for bedroom receptacle circuits and then sure enough, 2002 rolls around and they are required for all bedroom circuits not just receptacles and now required almost everywhere in a house and expanding to dorms etc.

Change the code = sell more product.


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PostPosted: Thu Jan 30, 2014 6:35 am 
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C. Marsh wrote:
Change the code = sell more product.

Change the code = sell new products with a premium.
Repeat.


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PostPosted: Mon Feb 17, 2014 9:35 am 
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C. Marsh wrote:
I'm wondering which manufacturer(s) got this wording changed. ...


That's an interesting question. Can this change be traced to a specific comment in the meeting agenda notes? Did this comment include an author or was it anonymous?

http://www.nfpa.org/codes-and-standards/document-information-pages?mode=code&code=70e&tab=nextedition


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PostPosted: Mon Feb 17, 2014 4:37 pm 
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C. Marsh wrote:
I'm wondering which manufacturer(s) got this wording changed. I understood if the breaker had no instantaneous but ALL breakers 1200A and above? REALLY??? :mad:


From my understanding the electrical inspection community pushed for this change. Their viewpoint was that the majority of inspectors are not trained to identify whether a breaker has an instantaneous element and whether that element is set, so they could not properly enforce the text as written in the 2012 code. They wanted a simpler way to determine if 240.87 applied to any particular breaker that they encounter in the field. I am aware of several manufacturers that are also quite upset about this change.

MattB wrote:
That's an interesting question. Can this change be traced to a specific comment in the meeting agenda notes? Did this comment include an author or was it anonymous?


You can review all of the proposals and the Code Making Panel action on the proposal in the "Report on Proposals" and "Report on Comments" documents for the 2014 revision cycle. First, [url='http://www.nfpa.org/codes-and-standards/document-information-pages?mode=code&code=70&tab=docinfo']click this link[/url][url='http://www.nfpa.org/codes-and-standards/document-information-pages?mode=code&code=70&tab=docinfo']then click the link for "Read the archived revision information".[/url]

Alternately, here is a direct [url='http://www.nfpa.org/Assets/files/AboutTheCodes/70/70-A2013-ROP.pdf']link to the ROP[/url], and here is a [url='http://www.nfpa.org/Assets/files/AboutTheCodes/70/70-A2013-ROC.pdf']link to the ROC[/url].


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