250.64(C)(3) in NEC2005

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iowadean

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In section 250.64(C)(3) in the 2005 NEC, a dimension is given for a busbar - 1/4 inch by 2 inches.
Does this refer to a busbar typically found in a residential panel that is 1/4 inch wide and at least 2 inches long or the type that might be found in commercial switching gear where the busbar is 1/4 inch thick, 2 inches wide and as long as needed to make the necessary connections?
If you know, please submit a code change to make this section a little clearer.
 
Re: 250.64(C)(3) in NEC2005

Originally posted by iowadean:
...
If you know, please submit a code change to make this section a little clearer.
Click to expand...
If you know how you would like it reworded, please post it as a proposal on our 2008 Proposals Forum.

That being said, the reasonable interpretation is the cross-section dimensions of the bus.
 
Re: 250.64(C)(3) in NEC2005

The 1/4" X 2" is a value given to establish the minimum size of a busbar that may be used to interconnect bonding jumpers from the various electrodes that are required to form the premises grounding electrode system of 250.50. Part III.

Actually it is the equivalent of a 636 kCmil conductor.

Convert inches to mils
250
2000
Find sq. mils 250 x 2000 = 500,000 Sq Mils

Acmil = A mil Sq / .7854

500,000 / .7854 = 636,618 Cir Mils.

The intent is for this bus to be located anywhere acceptable to make the connections for the bonding jumpers.

Charlie
 
Re: 250.64(C)(3) in NEC2005

I'm still confused. I just attended a code change meeting and the opinions in the room were pretty well split over what these dimensions are referring to. This confusion is fueled in part by the illustration on page 97 of the "Analysis of Changes" book that I got at the Western Section meeting of the IAEI. It shows a equipment grounding bar similar to what might be found in a residential panel. It would have a cross section of 1/4 inch by 2 inches if you cut it in half lengthwise.
 
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