Arc Flash labels - how many?

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dinos

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I am wondering how many arc flash labels are typically applied to a given piece of equipment.

As an example, for a motor control center which incorporates a main circuit breaker in its assembly, would there be one label on the main cb cubicle based on the arc flash energy available at the line side of the main cb, and then each bucket would have its own label based on the arc flash available at the line side of its feeder cb?

If however the motor control center did not incorporate a main circuit breaker in its assembly, would one arc flash label (placed on the main lug cover for example) suffice or is it necessary to place a label on each bucket as well?

Presumably the MCC situation would be similar to other equipment where protective devices are 'compartmentalized' (ie switchboards, fused switch distribution panels, etc)?

Lastly, for equipment where all of the bus is 'exposed' when the cover/trim is removed (for example a typical branch circuit panel having a main circuit breaker), presumably only one label is necessary based on the arc flash energy available at the line side of the main cb?

Thanks in advance for any guidance
 
dinos said:
I am wondering how many arc flash labels are typically applied to a given piece of equipment.

As an example, for a motor control center which incorporates a main circuit breaker in its assembly, would there be one label on the main cb cubicle based on the arc flash energy available at the line side of the main cb, and then each bucket would have its own label based on the arc flash available at the line side of its feeder cb?
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That is the way it is usually done

dinos said:
If however the motor control center did not incorporate a main circuit breaker in its assembly, would one arc flash label (placed on the main lug cover for example) suffice or is it necessary to place a label on each bucket as well?
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You can use just 1 label but it needs to be clearly visiable from each bucket. Using one label could lead to a legal argurement if something bad happened but meets the intent of the code.

dinos said:
Lastly, for equipment where all of the bus is 'exposed' when the cover/trim is removed (for example a typical branch circuit panel having a main circuit breaker), presumably only one label is necessary based on the arc flash energy available at the line side of the main cb?

Thanks in advance for any guidance
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Yep
 
Location of labels is not addressed by NFPA 70E.

Your electrical Safe Work Practices program should include information on where employees need to look for the arc flash information label for each piece of equipment.

I have never installed labels on each and every bucket of a motor control center. The location I was at yesterday, had us installing labels on the wireway door of each vertical section (so far we have installed more than 10,000 labels for this customer).

In my company's opinion, many, if not most, 600V motor control centers do not have sufficient compartmentalization to prevent a load side arc from propagating to the line side of a main protective device. Our recommendation is to use one value for an entire MCC.
 
jim dungar said:
I have never installed labels on each and every bucket of a motor control center. The location I was at yesterday, had us installing labels on the wireway door of each vertical section (so far we have installed more than 10,000 labels for this customer).
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I feel the pain in that statement, and that is just what I am trying to head off.

While I admire the practice of providing warning labels, the nitty gritty details of where to apply them seems to be rather difficult in practice.

After printing out the labels from our arc-flash software, I try to put myself in the position of understanding how the information is presented on the label so:

a) the person who has to stick them on in the field knows which exactly which equipment to put them on and where on the equipment is the best place for them to go.

b) the person who has to work on the equipment understands how the applied label(s) pertain to the compartment they intend to work in.

To a large extent, how bus names and protective device names are entered in the arc-flash software is crucial to getting them stuck in the right places, but even when I'm being careful with the designations I find that how the information is printed on the label is not always readily understood.
 
dinos said:
To a large extent, how bus names and protective device names are entered in the arc-flash software is crucial to getting them stuck in the right places, but even when I'm being careful with the designations I find that how the information is printed on the label is not always readily understood.
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I found it necessary to quote myself on this point...

There is a world of difference (cost) in applying generic style (e.g. "Arc Flash Hazard - Appropriate PPE Required") warning labels compared to those that specify the actual equipment name and the required level of PPE.
 
We install one calculated label per motor control center, usually in the center of the top wireway. Like Jim stated, in practical terms the incident energy is the same for the whole MCC.

We use one label per about 15 ft of legth of switchgear to ensure that a label is within sight anywhere along the lineup. A small single-ended lineup would get one label, but a 34.5 kV lineup 80 feet long gets a label on each 40 inch wide cubicle. Double ended 480V or 5 kV lineups might get 2-3 labels depending on size. We have outdoor NEMA 7 switchracks as well that are labeled every ten feet on each side of the bus box on top.
 
jim dungar said:
What NEC section tells you where to put the NFPA 70E require labels, and how many to install?
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110.16 talks about "location" which is what you said in your ealier post that I quoted. It says nothing about exactly where to put them and says nothing about how many. You are changing the quote.

As I said earlier 110.16 says the markings need to be clearly visible to any person doing any work on that equipment, including adjustment, servicing, or maintenance. (I am going from memory here, no NEC in front of me but it is along those lines).
 
zog said:
110.16 talks about "location" which is what you said in your ealier post that I quoted. It says nothing about exactly where to put them and says nothing about how many. You are changing the quote.

As I said earlier 110.16 says the markings need to be clearly visible to any person doing any work on that equipment, including adjustment, servicing, or maintenance. (I am going from memory here, no NEC in front of me but it is along those lines).
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110.16 says nothing about where to locate the NFPA 70E label. It does say that the field marking that warns about an arc flash hazard shall be located to be "clearly visible to qualified persons".

So the location and quantity of NFPA 70E labels needs to be part of the company's Electrical Safe Work Practice program.
 
jim dungar said:
110.16 says nothing about where to locate the NFPA 70E label. It does say that the field marking that warns about an arc flash hazard shall be located to be "clearly visible to qualified persons".
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Exactly what I said. And saying it needs to be clearly visible gives the only guideance there is for location.

jim dungar said:
So the location and quantity of NFPA 70E labels needs to be part of the company's Electrical Safe Work Practice program.
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Yep, the peeps need to be trained on where to look for them.
 
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