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 Post subject: Arc Flash Enclosure Size and Bus Configuration Study
PostPosted: Tue Jul 09, 2019 11:17 am 
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Joined: Fri Apr 15, 2011 7:43 am
Posts: 177
Location: Colorado
Has any one done a study of how the enclosure size and/or the configuration actually changes the IE values? Reason I am asking is we work in an industry where we cannot open equipment energized and we cannot get a shut down.

We are trying to figure out how we can still do studies without this information or if we can use some default information. I have client that have not addressed the new requirements but are asking for the 2018 calculations.

Not trying to get around collecting data but trying to figure out how to do studies without required data - sort of like getting utility data.


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 Post subject: Re: Arc Flash Enclosure Size and Bus Configuration Study
PostPosted: Sun Jul 14, 2019 2:28 pm 
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Joined: Mon Sep 17, 2007 5:00 pm
Posts: 1503
Location: Scottsdale, Arizona
Not that this is right or wrong but most so far are going with software defaults which are standard sizes from IEEE 1584. No one measured bus gaps with the 2002 edition even though they could. They went with defaults gaps back then. A similar thing is happening again.

Configuration is another matter. I believe software defaults to VCB which is the same as 2002 (someone let me know if a S/W company is doing something different from this). So if no major changes occur, this will get you closest to previous answers although numbers do go up and down.

Some are evaluating and defining configurations and a few said they will default to the worst case (which makes you feel sorry for the person wearing the PPE)

Since this is an IEEE 1584 question: My usual disclaimer, this is my opinion and not an opinion from IEEE.


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 Post subject: Re: Arc Flash Enclosure Size and Bus Configuration Study
PostPosted: Mon Jul 15, 2019 7:48 am 
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Joined: Tue Oct 26, 2010 5:00 pm
Posts: 188
Location: Maple Valley, WA.
We are using the default bus gap for equipment that is in an enclosure. For outdoor equipment not in an enclosure, we are using the minimum bus bar spacing.

For the enclosure sizes, we are measuring (the best we can) the enclosure sizes. For SWBDs, MCCs, SWGR, and others with multiple compartments, we are using the smallest enclosure.

For bus bar configuration, we are using some of the examples in IEEE 1584 as defaults. We have also developed a list of equipment with default electrode configurations based upon typical equipment.

_________________
Robert Fuhr, P.E.; P.Eng.
PowerStudies


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 Post subject: Re: Arc Flash Enclosure Size and Bus Configuration Study
PostPosted: Mon Jul 15, 2019 8:12 am 
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Joined: Fri Apr 15, 2011 7:43 am
Posts: 177
Location: Colorado
Thank you Jim. This has been a concern of mine since I heard it discussed in the ESW meetings. We are just getting to the point where we are being asked to use the 2018 - 1584. This does fall in-line with your latest Electrical Contractor article.


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 Post subject: Re: Arc Flash Enclosure Size and Bus Configuration Study
PostPosted: Mon Jul 22, 2019 4:46 am 
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Joined: Thu Jul 07, 2011 6:03 am
Posts: 64
Location: Netherlands
It's worth setting up an Excel sheet that calculates CF just to get a feel for it. I made one to help me determine a strategy on what to gather during data collection. In the intermediate incident energy calculation enclosure size turns up as 1/CF so its effect is very straightforward: a CF of 1.10 means a 10% reduction in arc flash energy. The largest difference you'll see is about 25% reduction in LV distribution so it's not something you want to spend a lot of effort on.

My data collection strategy is roughly as follows:

Are *any* compartments less than 20 in by 20 in?
If yes -> use width, height and depth of 20 in
If no -> note the smallest compartment width & height, do not overestimate.
(note that this ignores depth and 'shallow' panels completely, I haven't found a situation where this would be useful to consider)

If applicable, I note enclosure size and electrode configuration separately for incoming panels and the rest of the board. I have a magnetic ruler that I put on the cabinet when taking pictures, that really helps in quickly estimating enclosure sizes. For subdistribution I'll probably start using 20x20x20 inch as a default and only determining if it's HCB or VCBB as enclosure size rarely seems to matter.


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