Grounding vs Bonding Online Training

This article was posted 11/30/-0001 and is most likely outdated.

Grounding vs Bonding Online Training 14

September 16, 2005

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 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 to view the video [ 8MB ]

Below is the full course page which includes these videos:

Grounding versus Bonding

PART II.

Page 4 of 13

Sections

250.24 Grounding and Bonding at Service Equipment Continued

(C) Grounded Neutral Conductor Required. Because electric utilities aren’t required to provide an equipment grounding (bonding) conductor to service equipment, a grounded neutral service conductor must be run from the electric utility transformer to each service disconnecting means and it must be bonded to each service disconnecting means as required by 250.24(B) [250.130(A)]. Figures 250–54 and 250–55

Author’s Comment: The grounded neutral service conductor provides the effective ground-fault current path to the power source to ensure that dangerous voltage from a ground fault will be quickly removed by opening the circuit-protection device [250.4(A)(3) and 250.4(A)(5)]. Figure 250–56

DANGER: Because the resistance of the earth, when used as a ground-fault current path is so great, often as much as 500 ohms, very little fault current returns to the power source if it is the only fault-current return path. The result—the circuit overcurrent protection device will not open and clear the ground fault and all metal parts associated with the electrical installation, metal piping, and structural building steel will become and remain energized by circuit voltage. Figure 250–57

Figure 250–54
(Click on image to enlarge)

Figure 250–55
(Click on image to enlarge)

Figure 250–56
(Click on image to enlarge)

Figure 250–57
(Click on image to enlarge)

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
ISBN: N/A
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

Comments

Mike, in reading "Grounding versus Bonding" Part II, the text of 250.24 (C) states that a neutral conductor must be installed from the utility transformer to each service disconnecting means and be bonded to each service disconnecting means.

Please help me understand how this is applied for the connection of service for fire pumps fed directly from the utility transformer. The fire pump is fed with the three phase conductors only.

Is a neutral conductor to be installed to the fire pump automatic transfer switch?

Does the fire pump xfer switch/control panel to be furnished with a neutral bus (to accommodate multiple conductors), a ground bus and a removeable link?

Harvey Wilmoth
Reply to this comment

Services in San Diego where there is a transformer vault in the building and the service is over 2000 amps are required to be fed with bus duct. The neutral in the transformer is bonded to the transformer case and grounded. Then the neutral is also required to be bonded to the ground system in the service. This puts a parallel path for the neutral current on the outside case of the bus duct. I have asked the head inspector about this and they are steadfast about keeping it that way indicating that the bus and transformer should be considered to be utility controlled and outside the building. I don't see this as proper because it still puts objectionable currents on the ground path. It is my contention that the neutral IS bonded to the service disconnect switch by the equipment ground (bus case) going back to the transformer. Is my argument valid?

Thomas Kelly
Reply to this comment

Mike, Why is it that I get an amprage reading on a residence indoor power panel, when all the breakers on the panel are off and there is no load coming out of the bus bar.

Reply to this comment

Add Your Comments to this Newsletter


* Your Name:	Your name will appear under your comments.
* Your Email:	Your email address is not displayed.
* Comments:	This newsletter is closed to new comments. Email Notification Options: Notify me when a reply is posted to this comment Notify me whenever a comment is posted to this newsletter