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

[Joseph M. Whitt]

Originally Posted by Mike Whitt

Joe

Being that I am the only Mike that has responded in the thread are you addressing me?

If so please do me a favor and explain yourself a little clearer as I am nothing more than a lowly hillbilly that just don't understand.

Joe
I now understand what you were doing

[Marcel R. Cyr]

Originally Posted by Marc D. Shunk

For continuity's sake, probably so. The voltages called out in that sentence show that the material is probably dated. It's not technically incorrect, but just old nomenclature. In 2008, we'd typically refer to the nominal system voltages as 120 and 240. In the 1960's, we'd have probably been saying 115 and 230.

Mark, would this be correct also;


In the US and Canada, 220 volts, 230 volts, and 240 volts are used interchangeably to describe one voltage range that is used to power larger appliances. Similarly, 110 volts, 115 volts, and 120 volts all refer to the one voltage range that is available through the common electrical outlet. The sources of these seemingly different numbers is as follows:

• The 220 volt and 110 volt designations are older and familiar terminology, but are no longer used in either product design or by electric utilities in the US and Canada.
• The 230 volt and 115 volt terminology comes from equipment design standards. Equipment is commonly designed to operate at 230 or 115 volts plus or minus 10%.
• Electric utilities typically deliver electricity, under standard conditions, at 240 volts and 120 volts plus or minus 5% at the transformer.

When one takes into account that equipment is designed to accept voltage variations of 10% at a minimum and that the electric utility regularly delivers electricity within 5% of their standard, there is a good match between the voltage the electric utility delivers and the voltage equipment was designed to use.

Marcel

[Marcel R. Cyr]

Welcome aboard Mr. Whitt.

Marcel

[Joseph M. Whitt]

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.


Flow Quiz

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.

[Kenton H. Shepard, CMI]

Originally Posted by Marc D. Shunk

For continuity's sake, probably so. The voltages called out in that sentence show that the material is probably dated. It's not technically incorrect, but just old nomenclature. In 2008, we'd typically refer to the nominal system voltages as 120 and 240. In the 1960's, we'd have probably been saying 115 and 230.

On jobs over the years (CA and CO) I always heard 110 and 220.
My understanding is that measured near the transformer, the voltage is 120 at each hot conductor. At the main panel the two bus bars are combined by some breakers to supply 240 volts, but due to some current loss to resistance in the wires between the panel and the transformer on the utility pole, each leg is actuially a little less than 120 volts, and by the time current reaches the outlets furthest from the main panel, the voltage measured at the outlet may have dropped as low as 110 and 220 volts.

right?

[Michael Larson]

220 221 what ever it takes.

[Kenton H. Shepard, CMI]

Originally Posted by mlarson

220 221 what ever it takes.

I always liked Martin Mull.

[Marcel R. Cyr]

Originally Posted by mlarson

220 221 what ever it takes.

Mike I will up you 222

[Michael Larson]

Originally Posted by kshepard

I always liked Martin Mull.

Michael Keaton in Mr. Mom

[Kenton H. Shepard, CMI]

Originally Posted by mlarson

Michael Keaton in Mr. Mom

Yep, Michael Keaton talking to Martin Mull.

[Michael Larson]

Originally Posted by kshepard

Yep, Michael Keaton talking to Martin Mull.

Ah, I see,

[Larry D. Kage]

Originally Posted by mcyr

Welcome aboard Mr. Whitt.

Marcel

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