2011 Changes to the NEC – 240.4

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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.

240.4(B)(1) Overcurrent Devices Rated 800 Amperes or Less

The allowance for the next higher standard overcurrent device has been revised for consistency.

240.4 Protection of Conductors.

(B) Overcurrent Devices Rated 800A or Less. The next higher standard rating of overcurrent device listed in 240.6 (above the ampacity of the ungrounded conductors being protected) is permitted, provided all of the following conditions are met:

(1) The conductors aren’t part of a branch circuit supplying more than one receptacle for cord-and-plug-connected loads.

(2) The ampacity of a conductor, after the application of ambient temperature correction [310.15(B)(2)(a)], conductor bundling adjustment [310.15(B)(3)(a)], or both, doesn’t correspond with the standard rating of a fuse or circuit breaker in 240.6(A).

(3) The overcurrent device rating doesn’t exceed 800A.

Example: A 400A overcurrent device can protect 500 kcmil conductors, where each conductor has an ampacity of 380A at 75°C, in accordance with Table 310.15(B)(16).

Figure 240-1 (Click on image to enlarge)

Author’s Comment: This “next size up” rule doesn’t apply to feeder tap conductors [240.21(B)] or transformer secondary conductors [240.21(C)].

ANALYSIS: This subsection was changed to provide consistency with 210.19(A)(2), which applies to conductors supplying more than one receptacle. This change more clearly establishes the intent of this section, and eliminates a subtle conflict between these two sections.

 

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