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 Post subject: IEEE 1584 and Overdutied Breakers
PostPosted: Mon Oct 03, 2016 10:14 am 
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I guess this directed at IEEE 1584 Committee members (Jim) and I know you can't say too much but is overdutied breakers/equipment going to addressed in the new IEEE 1584?

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 Post subject: Re: IEEE 1584 and Overdutied Breakers
PostPosted: Mon Oct 03, 2016 11:30 am 
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There has been some ongoing debate on this topic. I can't speculate what will or won't be in the revised 1584 standard since we don't truly know the contents until it is balloted, the ballot comments addressed, and the document formally published.

There is one school of thought that says protective device duty is adequately covered by other standards, like the NEC, IEEE Violet Book, and IEEE 1584.1. If we attempted to put language about equipment duty in 1584 we could risk a conflict with a future revision of a different standard which could be confusing for the reader. Personally, I understand why folks engaged in arc flash analysis may want guidance on this topic. However from a wider perspective, overdutied equipment is already addressed by NFPA 70-2015 article 110.9. OSHA standards may also explicitly state that overdutied equipment is not permitted, I haven't looked though.

If a protective device is overdutied that information would be relevant input to the risk analysis which should be conducted in accordance with NFPA 70E-2015. Several facilities have used the risk assessment process to develop ideas like these:

- Policies stating operation of overdutied equipment is not permitted until all power sources to the overdutied equipment have been removed.
- Overdutied protective devices are not used in arc flash calculations. The next upstream device (or the 2 second cutoff) are used to calculate thermal energy exposure.
- When overdutied equipment is discovered it is immediately rectified, typical for inexpensive items like molded case breakers or panelboards.
- When overdutied equipment cannot be corrected quickly and inexpensively capital funding requests are submitted to attempt to secure funding to address the issue.


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 Post subject: Re: IEEE 1584 and Overdutied Breakers
PostPosted: Tue Oct 04, 2016 3:14 am 
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JD Smith provided a good answer. The IEEE 1584 Working Group has a set scope that they need to stay within and part of the challenge is sticking to it. Overdutied circuit breakers (and other equipment) is a real concern but it is in various other standards and we don't want duplication to occur - which can ultimately lead to different standards being out of synch when addressing the same topic.


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 Post subject: Re: IEEE 1584 and Overdutied Breakers
PostPosted: Tue Oct 04, 2016 4:10 am 
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Thanks all. The reason I asked is I have been involved in a discussion on another site concerning overdutied breakers and arc flash. I stated that if it is overdutied, it should be ignored in the analysis and the next upstream device not overdutied should be used regardless if the arcing current is below the AIC rating of the breaker.

I have been challenged to cite a standard saying to do that and I tried the fact that it is a NEC violation and the condition of the breaker must be considered. I know there is no hard and fast rule saying use next upstream breaker but it seems like good engineering practice but I was told I am in the minority and this person knows many engineers/firms that do not share that view.

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 Post subject: Re: IEEE 1584 and Overdutied Breakers
PostPosted: Tue Oct 04, 2016 9:30 am 
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wbd wrote:
I stated that if it is overdutied, it should be ignored in the analysis and the next upstream device not overdutied should be used regardless if the arcing current is below the AIC rating of the breaker.

I go along with JDSmith's position that the device being overdutied is considered as part of the Risk Analysis portion of an NFPA-70E study.
I recently reviewed a report which suggested a 'Dangerous' label for a 208V lighting panel supplied from a 45kVA 480-208Y/120 transformer which was being fed by an overdutied breaker. The fault current at the panel was calculated to be 2.23kA @208V, which means the current through the feeder breaker (rated 10kA) would not exceed 1KA

As I thought about your position it struck me, if the device cannot be trusted to clear an arcing fault, then should it also be removed from any selective coordination study?


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 Post subject: Re: IEEE 1584 and Overdutied Breakers
PostPosted: Wed Oct 05, 2016 2:37 pm 
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Two things. The concern is will it trip. With fuses yes but the device may not survive. With breakers arcing faults may trip although not short circuits. So handle each one appropriately. I've also found lots of cases where "conservative" engineering produced nonsensical results. And the short circuit method used can often report over dutied conditions that don't exist with more precise models (ANSI vs. IEC).


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 Post subject: Re: IEEE 1584 and Overdutied Breakers
PostPosted: Wed Oct 05, 2016 4:53 pm 
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A bit more about this.

I asked the question about overdutied devices in 2011. Here is the thread.

http://www.arcflashforum.com/viewtopic.php?f=33&t=1739&hilit=interrupting+rating

On other thing to consider is liability. If you know about it, ignore it and something happens.......


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 Post subject: Re: IEEE 1584 and Overdutied Breakers
PostPosted: Thu Oct 06, 2016 10:43 am 
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wbd wrote:
Thanks all. The reason I asked is I have been involved in a discussion on another site concerning overdutied breakers and arc flash. I stated that if it is overdutied, it should be ignored in the analysis and the next upstream device not overdutied should be used regardless if the arcing current is below the AIC rating of the breaker.


If the current of concern is within the breaker's rating, I fail to see how it can be considered to be overdutied in this situation.


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 Post subject: Re: IEEE 1584 and Overdutied Breakers
PostPosted: Thu Oct 06, 2016 5:53 pm 
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Jim Phillips (brainfiller) wrote:
On other thing to consider is liability. If you know about it, ignore it and something happens.......


I haven't seen anyone saying to 'ignore it'. I believe the issue is what to do with it until it has been replaced.

Position #1) do not allow the device to be used for normal operations (install a do not operate label) and pretend it doesn't exist when calculating AFIE
Position #2) allow the device to be used for normal operations that do not involve a bolted fault.


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 Post subject: Re: IEEE 1584 and Overdutied Breakers
PostPosted: Mon Oct 10, 2016 11:41 am 
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"If the current of concern is within the breaker's rating, I fail to see how it can be considered to be overdutied in this situation."

While I largely agree, that it makes sense.....
I can also see where it can become a "bookkeeping" nightmare, if you take it to logical extremes.
Say the overdutied device is the breaker for a cable riser, with taps at X, Y, and Z. The arcing and bolted faults exceed the riser-feeder rating at X, only the bolted fault exceeds it at Y, and neither exceeds it at Z. You have to keep separate track of each case. Not impossible, but I don't know that any of the software packages do that for you. Then there is the issue of "what do you do for the NEXT level downstream?". If you have full coordination fine, but what if you do not?
I don't think any of the software packages look at coordination on a "conditional" basis.

What about the upstream coordination? perhaps the Riser-feeder and Its main are so badly coordinated that the Main (presumably properly rated) clears all faults over the riser-feeders IC?
In that case do you ignore the feeder-riser for calculations at X, Y, and Z, or just X and Y, just X?


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