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Sec.110.24 #200259 03/26/11 08:11 PM
Joined: Feb 2002
Posts: 2,233
harold endean Offline OP
Let me see if I get this right. I just got my new 2011 NEC Analysis of the 2011 and under sec. 110.24 you are going to be required to field mark the Available Fault Current at the service equipment.
OK, that sounds safe, but do you think it would really work? What will happen if the POCO changes out transformers on the street a week or two later? Will they come into the building and remark the service equipment?

I am not trying to be a bad boy or anything, just trying to play devils advocate and trying to see things through in the real world.

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Re: Sec.110.24 [Re: harold endean] #200270 03/27/11 08:41 AM
Joined: May 2005
Posts: 984
ghost307 Offline
According to the folks who presented this subject at IAEI who were behind that part of 110.24 their intention was only to make the NEC tell you that there could be a hazard. As long as you don't open the covers to work anything live that's all you need.
If you were going to get close to unguarded conductors or bus, then then OSHA regulations would require that you do all the math and post the values on the outside.

There's no way that a calculated value will be valid forever...I'm reworking a place now that was first electrified bask when open-front black slate switchboards were considered cutting edge technology. Somehow I would not blindly trust any values written the original warning labels.
It was kind of amusing when we had folks bidding on the work; one guy saw the old board and refused to believe that all of the power for the whole place came through that 'antique'. He kept looking all over the building for "the real main electrical service".
If he submits the winning bid, this could get interesting very quickly.

Re: Sec.110.24 [Re: harold endean] #200295 03/27/11 08:08 PM
Joined: Apr 2002
Posts: 7,238
HotLine1 Offline

Please don't confuse 110.16 Arc Flash Hazard Warning with 110.24 Available Fault Current labeling and calculations.

Re: Sec.110.24 [Re: harold endean] #200298 03/27/11 10:37 PM
Joined: May 2005
Posts: 984
ghost307 Offline
Sorry, folks.
I misread the original post; but I hear so much from clients about having to calculate and list the arc flash data on equipment that I jumped to the wrong conclusion.
Thanks for catching my error.

Re: Sec.110.24 [Re: harold endean] #200309 03/28/11 10:01 AM
Joined: Apr 2002
Posts: 7,238
HotLine1 Offline
Apology was not necessary; that is a common misconception of the two terms.

There's a thread around somewhere that debated the terminology and differing opinions by a lot of us, myself included.



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