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2011 Changes to the NEC – 250.104
The following is an instructional page from our 2011 Changes to the NEC Textbook/DVD Package complete with graphics and video where applicable. As part of our on-going effort to provide free resources to help the industry, we will be sending this content as part of a series of newsletters. Each newsletter will feature pages taken directly from our textbooks. This can be a great training resource for your organization!
There are some important features in this text which help to highlight the changes that you should be aware of:
- Each Code section which contains a change includes a summary of the change, followed by a paraphrase of the NEC text affected by the change. Any specific change is denoted by underlined text and in the corresponding chapter color
- Graphics with green borders and 2011 CC icons next to the heading are graphics that contain a 2011 change; graphics without a green border or icon are graphics that support the concept being discussed, but nothing in the graphic was affected by a 2011 Code change.
250.104 Bonding of Piping Systems and Exposed Structural Metals
An Informational Note was added to alert the Code user that other standards are concerned with the bonding of gas piping systems. Additional text was also added to address buildings that don’t have a service.
250.104 Bonding of Piping Systems and Exposed Structural Metal.
(B) Other Metal-Piping Systems. Metal-piping systems such as sprinkler, gas, or air that are likely to become energized must be bonded. The equipment grounding conductor for the circuit that’s likely to energize the piping can serve as the bonding means.
Note: The National Fuel Gas Code, NFPA 54, Section 7.13 contains further information about bonding gas piping.
Author’s Comment: Informational Notes in the NEC are for information purposes only and aren’t enforceable as a requirement of the Code [90.5(C)].
(C) Structural Metal. Exposed structural metal that forms a metal building frame that’s likely to become energized must be bonded to the: Figure 250–80
Figure 250-80
• Service equipment enclosure,
• Service neutral conductor,
• Building/structure disconnecting means for buildings or structures supplied by a feeder or branch circuit,
• Grounding electrode conductor if of sufficient size, or
• Grounding electrode system.
Author’s Comment: This rule doesn’t require the bonding of sheet metal framing members (studs) or the metal skin of a wood frame building.
The bonding jumper must be sized in accordance with Table 250.66, based on the area of the ungrounded supply conductors. The bonding jumper must be copper where within 18 in. of the earth [250.64(A)], securely fastened to the surface on which it’s carried [250.64(B)], and adequately protected if exposed to physical damage [250.64(B)]. In addition, all points of attachment must be accessible, except as permitted in 250.68(A) Ex 2.
(D) Separately Derived Systems. Metal water piping systems and structural metal that forms a building frame must be bonded as required in (D)(1) through (D)(3).
(1) Metal Water Pipe. The nearest available point of the metal water piping system in the area served by a separately derived system must be bonded to the neutral point of the separately derived system where the grounding electrode conductor is connected. Figure 250–81
Figure 250-81
The bonding jumper must be sized in accordance with Table 250.66, based on the area of the largest ungrounded conductor of the derived system.
Ex 2: The metal water piping system is permitted to be bonded to the structural metal building frame if it serves as the grounding electrode [250.52(A)(1)] for the separately derived system. Figure 250–82
Figure 250-82
(2) Structural Metal. Exposed structural metal interconnected to form the building frame must be bonded to the neutral point of each separately derived system where the grounding electrode conductor is connected.
The bonding jumper must be sized in accordance with Table 250.66, based on the area of the largest ungrounded conductors of the derived system.
Ex 1: Bonding to the separately derived system isn’t required if the metal structural frame serves as the grounding electrode [250.52(A)(2)] for the separately derived system.
ANALYSIS: Previous editions of the Code required that structural metal likely to become energized be bonded to the service equipment enclosure. This doesn’t provide clear guidance in those cases when the building or structure is supplied by a feeder or branch circuit. This revision makes it clear that the structural metal (if likely to become energized) is to be bonded to the disconnecting means of the building or structure, regardless of the type of circuit feeding the premises.
An editorial change was also made to clarify that the point of bonding must be accessible except as permitted for fireproofed structural metal by 250.68(A) Ex 2.
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2011 NEC Changes DVD Package |
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Don't let the scale of the code changes intimidate you, this package will get you up to speed on the most essential 2011 NEC changes quickly. The book is well-organized, easy to follow, and the full-color illustrations bring the material to life. The DVDs bring together a group of experts from the field to discuss the changes and how they apply in the real-world.
This program includes the following items:
- Changes to the NEC 2011 Textbook
- Changes to the NEC 2011 DVD 1 & 2 includes Articles 90 - 810
Product Code: 11CCDVD
Price: $198.00
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