Arc Flash Labeling - Feeder Bus Duct

[PE (always learning)]

Hello everyone,

I have a question pertaining to arc flash labeling of feeder bus duct. I have a main distribution panel at 480V that has two 600A breakers. Both breakers feed (2) sets of (3) #350 KCMIL copper that feed over to a 600A bus duct run. My question is how do you provide labeling for the bus duct in this scenario? On previous projects I provided a label every 15-25 feet with the bus duct "worst case" label. The maintenance supervisor is asking for a label at each bus plug, which there are over a hundred on this project. This seems to be time consuming and expensive. If anyone has ever dealt with this issue when doing an arc flash evaluation, please let me know how you provided the labeling.

Best Regards,
Engineer in Training

 

[WA_Sparky]

Proper Labeling

Proper Labeling

Providing a label at every plug is overkill in my opinion. At the end of the day, it's up to the stamping engineer to decide how he wants to do the project. The code is somewhat vague and doesn't mention any specifics for bus ducts. Main purpose and function of these labels are to warn any qualified professional that is required to examine, adjust, service, or perform any maintenance on equipment while its energized, of any potential hazard or risk.

NFPA 70: 110.16 "the markings shall meet requirements in 110.21(b) and shall be located so as to be clearly visible to qualified persons before examination, adjustment, servicing, or perform any maintenance of the equipment".

110.21 just mentions labels need to be permanently fixed and durable.

I had a 7 story building with bus duct running from level 1-7. I only provided one sticker per floor, so anyone working on the equipment could see a big "WARNING" sticker. I don't see how it would be any different than a Main Distribution. You only need one visible sticker not one at each breaker. Our labels cost around $3.50 a pop with our own printer.

If he is not the stamping engineer that approved the calcs and is instructing you where to put them, or the one supplying the stickers, just ask him to show you a code reference. I think 15' spacing would be enough, as long as its clearly visible from all angles .

 

[PE (always learning)]

I agree that providing a label for each bus plug is definitely overkill.

"I think 15' spacing would be enough, as long as its clearly visible from all angles"

Because the bus duct is about 100 feet long, would you apply a new arc flash label with exact incident energy every 15 feet in order to accurately reflect what incident energy is seen at each location. Or would you just provide a "worst case" label with the same incident energy for each piece?

Best Regards

 

[jim dungar]

At the end of the day, it's up to the stamping engineer to decide how he wants to do the project.

Not quite.

it is actually up the employer's Electrical Safe Work Practices program.

 

[paulengr]

Not quite.

it is actually up the employer's Electrical Safe Work Practices program.

Not quite. It’s up to the contract terms if it’s an outside contractor. If the terms say comply with 70E that can mean all kinds of things. Like here’s your arc flash results, a copy of the 70E tables! Here’s your bill.



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