Hey Electricians... Can you help by proofing this new course?

mcyr · October 12, 2008, 12:34am

Mike I will up you 222;)

mlarson · October 12, 2008, 12:38am

Michael Keaton in Mr. Mom

kshepard · October 12, 2008, 12:42am

Yep, Michael Keaton talking to Martin Mull.

mlarson · October 12, 2008, 12:43am

Ah, I see,

lkage · October 12, 2008, 1:07am

Yes, welcome as a member. I’ve enjoyed your posts. Thank you.

Brian_A.MacNeish · October 12, 2008, 2:01am

Back in the 50’s-60’s, it used to be 110/220 but as households bought and used more electric appliances, installed electric heat and hot water heating appliances, problems of system voltage drop arose in periods of high demand. So they increased the voltage to 120/240 so that in these periods, voltage would not drop below the 110/220 that these appliances need to operate at. When I test the voltage in homes in my area, it’s usually in the 119-120 or 239/240 range.

A question arises though in that the higher extra voltage puts the average power bill up by 2-9% per month!!!

Marc_D.Shunk · October 12, 2008, 2:20am

Uh… no, not at all. Ohm’s law, brother. A kilowatt hour is still a kilowatt hour, no matter what voltage you’re served at. If your household appliances ran on one million volts, and you had a one million volt service, your kilowatt hours consumed would be identical or even ever so slightly less due to efficiencies gained at higher voltages.

mlarson · October 12, 2008, 2:33am

P=E²/R

A resistive load would result in increased kilowatts for the higher voltage.

jtedesco1 · October 12, 2008, 3:25am

jwhitt:

Any thing in red I changed
Anything in blue is my comment concerning the text posted.
Any and all feel free to comment on my statements.

**Terms **
Alternating current is an electric current that reverses its polarity at regular intervals. For example, it would alternate 60 times every second in a 60-cycle system. This type of power is commonly found in homes.
(I find that it is easier for the beginning student to understand the reversing of polarity than thinking of current reversing direction. This reversing leads to confusion as to which conductor is call “hot” and why the neutral is connected to earth when it is supposed to have current changing direction on it. )

**Neutral wire—**The third wire in a three-wire distribution circuit; it is usually white or light gray and is connected to the ground only at the service.
I think that it is important to insure that everyone understands that the neutral can be in contact with a grounding conductor only at the service.

Sort circuit—A connection between hot and neutral wires, hot and grounding wires or two hot wires.
When current stops flowing the path it takes or the circuit conductor have become open. The definition was more toward an open circuit than a short although the end of the sentence did describe a short.

Codes
4th paragraph
In the past, electrical systems could be grounded to the first five feet of the home’s plumbing system. Today, many plumbing systems are no longer constructed of conductive material, but are made of plastic or polyvinyl chloride-based materials. Today, the recommendations for grounding a home electrical system are to use two 8-foot by ⅝-inch copper ground rods. These must be spaced 6 feet apart and be connected by a continuous (unbroken) piece of copper wire (the size of this wire corresponds to the size of the system main). It is also required that the system be grounded to the incoming metal cold water supply line within the first five feet.
Let’s make sure that no one thinks that the metal water line can be used to ground the electrical system by simply hitting it anywhere. The requirement is within the first five feet.

Flow of Electric Current
For electric current to flow, it must travel from a higher to a lower potential voltage. In an electrical system, the hot wires (black or red) are at a higher potential than are the neutral or ground wire (white or green).
Completely delete this sentence as it is totally wrong. Current will always flow on a complete path. There must be a source of voltage and a path for the current to flow. The current is always trying to return to the source which has no high or low potential between itself.

The earth, by virtue of the moisture contained within the soil, serves as a very effective conductor. Therefore, in power transmission, instead of having both the hot and neutral wires carried by the transmission poles, one lead of the generator is connected to the ground, which serves as a conductor. All electrical utility wires are carried by the transmission towers and are considered hot or charged. At the house, or point where the electricity is to be used, the circuit is completed by another connection to the ground.
Again the author has use the earth as part of the return path. This is incorrect. The secondary side of the transformer that is supplying power to a building is in no way connected to the high voltage conductors that supply the primary side of the transformer. The current from the house is trying to return to the secondary side of the transformer through the neutral or in the event of a 240 volt circuit one or the other lines of the circuit.
The power company uses the earth only to clear faults not as a return path for their circuits.
The secondary of the transformer on the pole at each building being served is a separately derived system. It is in no way connected to the primary side.

The electric power utility provides a ground at the secondary side of the transformer. therefore, there is a ground wire in addition to the hot wires within the service drop. In FIGURE 11.1**,** this ground can be seen at the power pole that contains the step-down transformer.
I am not sure what the author is trying to point out with this statement. It is important that the student of this course understand that for the wiring system installed in a building the grounding electrode plays only one of three roles. 1) for lightning 2) power surges. This could be a short between the primary and the secondary of the transformer. 3) in the event one of the high voltage lines breaks and drops down across the service drop.
Using Ohm’s law we can see that in the event of either 2 or 3 the earth could carry enough current to open the overcurrent device on the primary of the transformer which will at most be a 20 amp fuse. (E=IXR) Knowing that the rod is to have 25 ohms or less to ground (250.56) and the primary in most cases is 7200 volts we can see that a total of 288 amps of current flow which would open the primary of the transformer.

In addition to the ground connection provided by the electric utility, every building is required to have an independent ground, called a system ground. The system ground is a connection to ground from one of the current-carrying conductors of the electrical system. System grounding, applied to limit overvoltages in the event of a fault, provides personnel safety, provides a positive means of detecting and isolating ground faults, and improves service reliability. Therefore, the system ground’s main purpose is to protect the electrical system itself –it offers limited protection to the user.
I must say that I just don’t understand how the author of this statement even comes close to being correct.
First it is the neutral of the incoming power that is connected to earth in most installations. Any installation where one of the phase conductors was connect to earth would be outside of any Home Inspector as it would have to be an industrial establishment. It is called a corner grounded system.
Again the grounding electrode serves only one purpose as outlined in 250.4 of the NEC, it is for lightning, power surges and unintentional contact with higher voltage lines.
If there is a ground fault in a properly installed system the overcurrent device will open even if there is no electrode installed at all. I just don’t understand what the author of this was trying to get across as every thing in this paragraph is incorrect.

The system ground serves the same purpose as the power company’s ground. However, it has a lower resistance because it is closer to the building. The equipment ground protects people from potential harm during the use of certain electrical equipment. The system ground should be a continuous wire of low resistance, and of sufficient size to conduct current safely from lightning and overloads.
True the two system grounds serve one of the same purposes but with the utility company their grounds also open faults where as the ground for the building does not. Again Ohm’s Law will prove this E=IxR With 25 ohms and 120 volts there would only be 4.8 amps of current and not enough to open the overcurrent device.
The grounding electrode offers no protection to the user, equipment, system or any other concept of the electrical system except for lightning, surges and contact with higher voltages.

It is my personal opinion that the author of this part of the quiz just doesn’t understand grounding and bonding theirself. This section of the course needs some attention and major changes needs to be make.

[FONT=Arial]Flow Quiz[/FONT]

[FONT=Arial]For electric current to flow, it must travel from…

a higher to a lower potential voltage.
a lower to a higher potential voltage.

Change the choices to 1) different potentials 2) same potentials

It is now time for the race which the wife snuggles close and watches with me. I just don’t want to miss having her sit so close to me and keeping my side warm.
I shall return to look at it some more later.

Edited to say thank you for all the warm welcomes. I can see that I have a lot to learn in a field that I don’t full understand as yet so I am expecting some of you to help guide me through me new adventure.

[/FONT]

Welcome Giuseppe!

Your complaints about what you read as being incorrect, and making suggested corrections should not be directed toward the person who claims to have written this, but to the following:

http://www.cdc.gov/nceh/publications/books/housing/housing.htm

ACKNOWLEDGMENTS

We acknowledge the suggestions, assistance, and review of numerous individuals and organizations that went into the original and current versions of this manual. The revisions to this manual were made by a team of environmental health, housing, and public health professionals led by Professor Joe Beck, Dr. Darryl Barnett, Dr. Gary Brown, Dr. Carolyn Harvey, Professor Worley Johnson, Dr. Steve Konkel, and Professor Charles Treser.

Individuals from the following organizations were involved in the various drafts of this manual:

Department of Housing and Urban Development (HUD), Healthy Homes and Lead Hazard Control,
U.S. Department of Health and Human Services (HHS), Centers for Disease Control and Prevention (CDC), National Center for Environmental Health (NCEH)
National Healthy Homes Training Center and Network
National Association of Housing and Redevelopment Officials
Department of Building, Housing and Zoning; Allentown, Pennsylvania
Code Enforcement Associates; East Orange, New Jersey
Eastern Kentucky University; Richmond, Kentucky
University of Washington; Seattle, Washington
Battelle Memorial Institute; Columbus, Ohio

Specifically, our gratitude goes to the following reviewers:
Dr. David Jacobs, Martin Nee, and Dr. Peter Ashley, HUD; Pat Bohan, East Central University; James Larue, The House Mender Inc.; Ellen Tohn, ERT Associates; Dr. Stephen Margolis, Emory University; and Joseph Ponessa and Rebecca Morley, Healthy Homes Training Center.

A special thank-you for assistance from Carolyn Case-Compton, Habitat for Humanity, 123 East Main Street, Morehead, Kentucky. Pictures of a home under construction are courtesy of Habitat for Humanity and John King, home builder and instructor, Rowan County Technical College, Morehead, Kentucky; and Don W. Johnson, building photographer of Habitat for Humanity.

In addition, a special thank you to the Environmental Health Services Branch and the following staff: CAPT Craig Shepherd and CAPT Michael Herring, Commissioned Corps, U.S. Public Health Service, for their research and review during the editing of this manual. Special thanks also to Pamela S. Wigington and Teresa M. Sims for their hard work preparing this manual for Web publication.

Marc_D.Shunk · October 12, 2008, 4:01am

… of which there are only a couple in a home when compared to the load total.

jwhitt · October 12, 2008, 1:03pm

jtedesco1:

Welcome Giuseppe!

Your complaints about what you read as being incorrect, and making suggested corrections should not be directed toward the person who claims to have written this, but to the following:

http://www.cdc.gov/nceh/publications/books/housing/housing.htm

ACKNOWLEDGMENTS

We acknowledge the suggestions, assistance, and review of numerous individuals and organizations that went into the original and current versions of this manual. The revisions to this manual were made by a team of environmental health, housing, and public health professionals led by Professor Joe Beck, Dr. Darryl Barnett, Dr. Gary Brown, Dr. Carolyn Harvey, Professor Worley Johnson, Dr. Steve Konkel, and Professor Charles Treser.

Individuals from the following organizations were involved in the various drafts of this manual:

Department of Housing and Urban Development (HUD), Healthy Homes and Lead Hazard Control,

U.S. Department of Health and Human Services (HHS), Centers for Disease Control and Prevention (CDC), National Center for Environmental Health (NCEH)

National Healthy Homes Training Center and Network

National Association of Housing and Redevelopment Officials

Department of Building, Housing and Zoning; Allentown, Pennsylvania

Code Enforcement Associates; East Orange, New Jersey

Eastern Kentucky University; Richmond, Kentucky

University of Washington; Seattle, Washington

Battelle Memorial Institute; Columbus, Ohio

Specifically, our gratitude goes to the following reviewers:
Dr. David Jacobs, Martin Nee, and Dr. Peter Ashley, HUD; Pat Bohan, East Central University; James Larue, The House Mender Inc.; Ellen Tohn, ERT Associates; Dr. Stephen Margolis, Emory University; and Joseph Ponessa and Rebecca Morley, Healthy Homes Training Center.

A special thank-you for assistance from Carolyn Case-Compton, Habitat for Humanity, 123 East Main Street, Morehead, Kentucky. Pictures of a home under construction are courtesy of Habitat for Humanity and John King, home builder and instructor, Rowan County Technical College, Morehead, Kentucky; and Don W. Johnson, building photographer of Habitat for Humanity.

In addition, a special thank you to the Environmental Health Services Branch and the following staff: CAPT Craig Shepherd and CAPT Michael Herring, Commissioned Corps, U.S. Public Health Service, for their research and review during the editing of this manual. Special thanks also to Pamela S. Wigington and Teresa M. Sims for their hard work preparing this manual for Web publication.

Joe
Once again you have me confused.

Nick asks that this be commented on and post here in this thread. I thought that he wanted this for continuing education for Home Inspectors.

Are you saying this is something that is going to be used for training material in Iraq?

jtedesco1 · October 12, 2008, 1:14pm

No not for training in IRAQ, you should search the text of this so called new material and see that it comes word for word from the CDC!

Get it now?

jwhitt · October 12, 2008, 2:04pm

We both know that a lot of the material contained within is completly wrong don’t we

jbushart · October 12, 2008, 2:08pm

Wrong…according to…?

Marc_D.Shunk · October 12, 2008, 2:15pm

I think the main objection is to the material being referred to as new or possibly unique to NACHI, and the requisite baiting of electricians to review it, where a membership would be required to do so. From a business standpoint, it was worth a try. Otherwise, it had the appearance of a low class ploy to the thinking man.

jtedesco1 · October 12, 2008, 2:27pm

Joey!

If you are having heartburn about what you see wrong tell the real authors about your problems!

jwhitt · October 12, 2008, 2:47pm

250.4(A)(5) Effective Ground-Fault Current Path. Electrical equipment and wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a low-impedance circuit facilitating the operation of the overcurrent device or ground detector for high-impedance grounded systems. It shall be capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a ground fault may occur to the electrical supply source. The earth shall not be considered as an effective ground-fault current path.

How about the NEC saying that some of the material covered in the text is absolutely incorrect!

The one thing that I have learned about this site is the inability of some to learn. They seem to be stuck is the yesteryear and refuse to budge.

There is a misconception that grounding or connecting to earth some how makes an electrical system safe. This is far from the truth. Bonding at the service is what makes an electrical system safe. The ground rod, water pipe, concrete encased electrode and the other five electrodes in no way makes the system safe, it only protects from;
250.4 General Requirements for Grounding and Bonding.
The following general requirements identify what grounding and bonding of electrical systems are required to accomplish. The prescriptive methods contained in Article 250 shall be followed to comply with the performance requirements of this section.
(A) Grounded Systems.
(1) Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.

It is the bonding of the equipment grounding conductors, service enclosure and grounding electrodes back to the source that protects equipment and personal from current flow;
250.4(A)(5) Effective Ground-Fault Current Path. Electrical equipment and wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a low-impedance circuit facilitating the operation of the overcurrent device or ground detector for high-impedance grounded systems. **It shall be capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a ground fault may occur to the [size=4]ELECTRICAL SUPPLY SOURCE.**The earth shall not be considered as an effective ground-fault current path.[/size]

According to the NEC it is incorrect. Then we have math that we can always fall back on. Ohm’s Law is a math equation and will prove that the earth is not a conductor for lower voltages such as 120/240.

jwhitt · October 12, 2008, 2:50pm

Because it was Nick that ask and not the real authors. Are you saying the material is correct?

jtedesco1 · October 12, 2008, 3:55pm

Sorry you do not understand yet!

Go ahead and waste your time for free, and our time with your comments!

jbushart · October 12, 2008, 3:56pm

I know that electricians limit themselves to this source, but I hope in reviewing HI courses you will take into consideration that the NEC is not the only code out there AND that home inspectors, unlike electricians, are not handcuffed by it.

Because the NEC is silent on certain things…Home Inspectors need not be. Additionally, we will use recent reports published by various agencies as references for conditions that we may feel to be unsafe…that are perfectly fine with NEC (purple wire nut copper pigtails to aluminum conductors comes to mind).

Wrong, according to the NEC, is not necessarily wrong for our purposes.