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 Post subject: The scope of Arc flash study
PostPosted: Mon Nov 19, 2012 2:01 pm 
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Do you provide arc flash label for the equipment such as humidifiers and fans? We normally provide labels for distribution equipment only like panels and MCCs etc., but one of our clients requested extra labels for the equipment they have in the facility. Do you normally include this in your original budget?


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PostPosted: Wed Nov 21, 2012 4:43 am 
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Location: North Carolina
Noah wrote:
Do you provide arc flash label for the equipment such as humidifiers and fans? We normally provide labels for distribution equipment only like panels and MCCs etc., but one of our clients requested extra labels for the equipment they have in the facility. Do you normally include this in your original budget?


NEC only requires it on a certain list of equipment which sounds like what you are describing.

In every bit of arc flash task training I've seen though, there is always a definition of a "cutoff" of some sort where below that point, there is a "default" set of rules to use. Some examples to consider:
1. All incident energy values are less than a fixed value. 1.2, 2, 4, and 8 are all common, depending on the industry.
2. Use the tables in 70E. The bit about trip times is always problematic.
3. Read the upstream label (common for motor peckerheads). Use with caution because sometimes incident energy values can increase.
4. All of the following equipment has the following value ___.often includes all 120 V cord-and-plug equipment. When you get to 208/240 V, the rules tend to be more varied (and there is a legitimate arc flash potential). Even some 480 V equipment may fall into this category if you have fast, small MCCB's protecting the receptacles. I recommend the newer kind that have receptacles with integrated disconnects and dead fronts that trap the plug so that you can't unplug while energized or plug in while energized.


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PostPosted: Mon Nov 26, 2012 10:00 am 
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There are two approaches: 1. Do the minimum required by code, or 2. provide a study that protects the people that we are trying to protect. I typically do the latter and that is what my client want. That being said I do not label everything thing in the plant. My thought process is any equipment that can be readily accessed when energized such as panels, disconnects - anything that can be opened with a few screws. Motors do not fall into this, generally, because they need to be opened and tape removed - much more deliberate. I also look if the device can actually be labeled, a 480V pin/sleeve may be labled - maybe, but a 480V- 15A receptacle probably cannot be labeled.


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PostPosted: Mon Nov 26, 2012 3:14 pm 
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Location: Maple Valley, WA.
We normally provide labels for distribution equipment shown on the one line diagrams or identified during the site visit. This includes control panels, panelboards, MCCs, transformers, Switchboards, substations etc. We will include and model motors greater than 50 HP as recommended by IEEE when performing short circuit studies.

We state in our quote how many pieces of electrical equipment that we will include. If the customer wants more or if we find more equipment (than found when we did the site survey), then we can include it for a cost of $50 to $85 per label. This is stated in our quotation so that there will be no surprises or disagreements.

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


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