Send to a Friend View / Add Comments  

Many of you have completed our Online Continuing Education Courses which include video instruction and know this is a very fast way to obtain your CEU credits from the comfort of the chair you're sitting in. For the rest of you we are sending a weekly series of newsletters featuring an instructional page complete with videos.

To view the videos you will need to download the free Real Player Download Real Player plugin for your browser - if you don't already have it. After installing Real Player, you can view the videos by clicking on one of these icons:

  • Click on this icon Hi Res - Cable/DSL to view the video [ 6.9MB ].

Below is the full course page which includes these videos:

[ Challenge Yourself - Take Our FREE Grounding vs. Bonding Exam ]

Grounding versus Bonding — 2005 NEC®
PART I   Hi Res - Cable/DSL        Page 6 of 13


250.4 General Requirements for Grounding and Bonding Continued

(A) Solidly Grounded Systems.

(4) Bonding Conductive Materials to an Effective Ground-Fault Current Path. To remove dangerous voltage from ground faults, electrically conductive metal water piping systems, metal sprinkler piping, metal gas piping, and other metal-piping systems, as well as exposed structural steel members that are likely to become energized, must be bonded to an effective ground-fault current path. Figure 250–21

Author’s Comment: The phrase “likely to become energized” is subject to interpretation by the authority having jurisdiction.

(5) Effective Ground-Fault Current Path. To remove dangerous voltage from ground faults, metal parts of electrical raceways, cables, enclosures, and equipment must be bonded to an effective ground-fault current path with an equipment grounding (bonding) conductor of a type specified in 250.118. Figure 250–22

Author’s Comment: To assure a low-impedance ground-fault current path, all circuit conductors must be grouped together in the same raceway, cable, or trench [300.3(B), 300.5(I), and 300.20(A)]. Figure 250–23

The earth is not considered an effective ground-fault current path.

DANGER: Because the resistance of the earth is so high, very little current returns to the electrical supply source via the earth. If a ground rod is used as the ground-fault current path, the circuit overcurrent protection device will not open and metal parts will remain energized.

For example, the maximum current flow to the power supply from a 120V ground fault to a 25? ground rod would only be 4.8A. Figure 250–24

I = E/R
I = 120V/25?
I = 4.8A

Figure 250–21
Click on Image to Enlarge

Figure 250–22
Click on Image to Enlarge

Figure 250–23
Click on Image to Enlarge

Figure 250–24
Click on Image to Enlarge

04. Grounding versus Bonding Library - DVDs
Grounding and bonding problems are at epidemic levels. Surveys repeatedly show a high percentage of power quality problems are due to poor grounding and bonding. Electrical theory has been applied to this difficult to understand Article, making it easier for students to grasp the concepts of grounding and bonding. Additionally, Mike has color coded the graphics so you can easily differentiate between grounding and bonding. For a limited time, you can order the Entire Grounding versus Bonding Library including the textbook, 2 videos, MP3 Audio CD and the Online Program for this great price. You save over $200!

Product Code: 05GBDVD
MultiMedia: Tape & CDROM & DVD

DVD/CD Return Policy: Unopened sealed DVD's or CD's may be returned within 10 days and we will credit your credit card or issue a refund for the price of the item(s). Opened items may not be returned unless they arrive defective.

Table of Contents
Sample Pages
Sample Graphic
  Send to a Friend View / Add Comments  

Copyright © 2005 Mike Holt Enterprises,Inc.
1-888-NEC-CODE (1-888-632-2633)