Article 525.11

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robertwilber

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I went to a training meeting the other evening and am in conflict with the presenter and many attendees of the program.
The position taken by most parties is that 525.11 says that the 12-foot spacing requirement applies to the location of the power sources.
I claim that they misunderstand the writing, and that the 12-foot spacing relates to the proximity of the equipment SUPPLIED by the various power sources.
To my understanding of the article as written, the purpose is to require that any two structures or rides that are within 12 feet of each other require that the power sources be bonded together, whether these sources were 10 feet or 100 feet apart. This view is supported by a forum entry I found from 2006.
The parties I disagreed with insist that the rule means merely that power supplies located within 12 feet of each other need to be bonded together. I find this suggestion ludicrous.
 
robertwilber said:
I went to a training meeting the other evening and am in conflict with the presenter and many attendees of the program.
The position taken by most parties is that 525.11 says that the 12-foot spacing requirement applies to the location of the power sources.
I claim that they misunderstand the writing, and that the 12-foot spacing relates to the proximity of the equipment SUPPLIED by the various power sources.
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This thread just led me to some interesting reading. One of the CMP-members that voted in the negative, not wanting to add this text to the 2005 code, even said it was unclear as to 'what had to be 12' apart.'

In reading the ROP (proposal was rejected) and the ROC (proposal was revived by the TCC) I would say you are correct. The intent of the proposal was to get the sources of power bonded together if the rides were 12' apart.

Despite the lack of technical substantiation (how does one generator push electrons seeking a return path back to their source via a different source), and the decrying of the dissenters to this fact, the proposal still ended up accepted as part of the 2005 NEC.

The parties I disagreed with insist that the rule means merely that power supplies located within 12 feet of each other need to be bonded together. I find this suggestion ludicrous.
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Hey, I understand their confusion. At first glance, it looked to me as though they were trying to define an area around each supply around each area for the application of 250.50. Two posts are two structures - how close do two temps have to be to use the same GES?

I originally thought that was the answer too, until I read the ROP/ROC. :)
 
I just went looking through the 2008 cycle, to see if things changed, and they will. Check out the text as of the ROC:

525.11 Multiple Sources of Supply. Where multiple services or separately derived systems, or both, supply portable structures, the equipment grounding conductors of all the sources of supply that serve such structures separated by less than 3.7 m (12 ft) shall be bonded together at the portable structures. The bonding conductor shall be copper and sized in accordance with Table 250.122 based on the largest overcurrent supplying the portable structures, but not smaller than No. 6 AWG.
Panel Statement: The panel is concerned that conductors smaller than No. 6 AWG copper will be subject to physical damage, therefore, a minimum size is defined.
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There were proposals gasping at the lack of technical substantiation (or evidence of a problem) continued in this cycle, but to their credit they did realize that requiring two GES's that could be hundreds of feet apart to be bonded, when there's two rides 10' apart that are actually bringing on the bonding, was retarded. :)

Sometimes I am very suprised at the lack of common sense at this level. Why get a GES involved at all (except as a relief method) if the purpose of a requirement is bonding? It seems to me "connect to the GES" is sometimes a knee-jerk reaction of wording rather than a well thought out and carefully used term.

It's no wonder half the planet doesn't get grounding versus bonding. The saga continues.
 
George, thanks for looking into this. When I read the first post, I thought "this is the '05 code?, I don't remember it in the '02." and "the trainer's version is beyond crazy". Having now looked at the 05, I suppose someone could read it that way.. (Having been on a good number of fair sites, both work and play, the probability of the sources being less that 12' from each other is rather small.)
 
Mike Holts material on 525.11 states "I have no clue what this is supposed to accomplish". Remember the 525 CMPs are not the grounding experts.
 
I think there is a valid issue here. There are multiple paths for current to flow and the intent of this proposal it to make sure there is no way a person can come into contact with two items that are at a different potential. If there is a fault on one, and the EGC path is compromised, then the two items could be at a different potential(not unlikely given the conditon of many carnival setups). The bonding removes this potential.
Don
 
I will say the 2008 requirement is an improvement over the 2005.

The problem I see with this is that an OCPD still will probably not open. Someone touching the faulting ride and a bolted-down trash can could still receive a lethal jolt, the bonding of the two rides together can't help that.

Unless the sources and the rides were bonded together, there would not be an effective redundant return path. I only see another ride being energized - sure, we can touch both at once, but we couldn't touch anything else. Am I off base here?
 
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