That sounds good, Paul. Thanks. 
Chris, I tried to take that course- it’s an online course- and got this:
From: Quality Education Group, Inc.
Sent: Wednesday, November 06, 2013 5:20 PM
To: kenton@internachi.org
Subject: Re: Oregon Online Registration
Kenton,
Sorry, but we do not sell courses to our competitors. We have voided your credit card payment, thus it will not show up on your credit card statement.
Dolores Hinchell
Gee I wonder is that legal to do, sounds to me like discrimination .
You might want to talk to the NACHI lawyer… Roy
Thus the reason I never take courses from Steve. QEG is local and based here in Illinois. Kind of surprised though cause he is a nice guy and I’ve never known him to have a beef with us Nachi folk…
hmmm…
First time I’ve ever contacted them.
It’s an online course, you can’t really prevent anyone from taking it. You can refuse to accept their credit card or give them access to the course, but how are they going to stop me from using a friend’s computer and credit card?
I suspect that they don’t have information about electrical that on one else has, and it’s illegal to use copyrighted work anyway, so I don’t see the problem, but I’m not going to worry about it.
Why?
I guess you used your “Nachi Card”.
Or else your name is known nationwide in the home inspector world. :mrgreen:
It’s a little ironic they don’t “sell to competitors”; then have have this on their site:
“Our online distance learning program allows you to earn your CE credit hours and MRC’s through home study courses whenever you want. All classes are accepted by ASHI,NAHI and iNACHI](http://www.nachi.org/). We offer home inspection pre-license training through our affiliate, Inspection Certification Associates.”
I don’t think I’m quite there. :mrgreen::mrgreen:
They saw my email signature.
I meant to say Worldwide.
I was a little confused by the original question because of the mention of “floating neutral”. After reading through some of the other replies, I realized that the question was about grounding and bonding methods, not a floating neutral. Others have done a good job of explaining why panels are bonded and grounded the way they are. I don’t have much to add to what others have said.
It is worth noting, however, that there is no “floating neutral” in a residential split-phase system. The neutral is always solidly grounded. Floating (including resistance) grounds are employed in certain applications for very specific reasons. A floating neutral would no longer be a neutral if it were floating. In other words, the terms “floating” and “neutral” are (in practice) mutually exclusive. In a practical application, a ground can float but a neutral cannot.
I covered the topic in great detail back in 2007 and 2008 in several of the the monthly online InterNACHI classes I used to do. I don’t know if any transcripts of the classes still exist. The last I knew, Hank was the curator of the transcripts.
The neutral in a properly assembled residential electrical system is always solidly grounded. Multiple connections between the grounded (aka neutral) and grounding conductors will result in potential (Voltage) between the conductors at various points.
I don’t want to get too technical but it is important to understand that electricity behaves differently at different Voltages and frequencies and with different waveforms. Not all faults are sinusoidal and may include harmonics.
Two electrical paths with the same resistance can have very big differences in impedance during a fault. An indirect lighting strike is a good example of a condition in which very large potentials could exist between two electrically conductive paths of similar resistance.
Therefore, the goal is to limit the number of ground references (paths to ground). Ideally, there would only be one ground reference.
The attached diagram is from IEEE Standard 142-2007:
Thanks George I am not able to explain things as well as some others are that was what I was trying to get across in post 19.
Many electricians have trouble with theory so trying to explain to a non electrician it becomes even harder .
There is a nominal 120V potential between the ungrounded conductor and the grounded conductor. The grounded conductor is connected to the center of the secondary winding of the transformer and to Earth.
In a perfect world, there would be no measurable potential between any two grounded conductors, any two grounding conductors, any grounded conductor and any grounding conductor, or any grounded conductor or grounding conductor and Earth. That would be the ideal but as a practical matter, there will always be a potential between any two reference points. For that matter, there will be a potential between any two points even if they are not connected to an electrical source but that is a topic for a more advanced discussion. The goal is to get that potential as close to zero as is practical.
To say that electricity is trying to return to its source is only partially correct. Electricians are often taught the “return to source” concept because it is more accurate than to say that it is trying to return to its source than to say that the electricity is trying to flow to Earth. Neither statement, however, is entirely correct. I wrote an article explaining this a few years ago. I’ll try to find it and I’ll post a link to it if I can find it.
Regardless of how we look at where the electricity is trying to go, the source under consideration is not the place where the electricity was generated. The source in a typical residential service is going to be the center tap of the secondary winding of the transformer. The transformer is usually going to be within a couple of hundred feet.
This is a good example of why I like to explain how electricity works rather than recite codes. Once you understand how electricity behaves, it is much easier to understand the codes.
You are on the right track with your thinking. This is where relying on electrical codes can do more to cause confusion that to make things clearer. The likelihood of having a problem where the panels are only a foot apart is extraordinarily slim. Having two electrical panels that are 20 or 30 feet apart is much more serious than two panels that are only a foot apart. At the same time, having two panels 20 or 30 feet apart is also more of a problem than two panels that are a mile apart. Codes try to keep it as simple and as practical as possible.
There is direct current (DC) and alternating current (AC)
Let’s look at the DC first. Think of a long tube and a handful of ping pong balls. The tube is completely full of these balls and we decide to put another ball in the pipe. The second we add one more to the tube one comes out the other end. The conductor is full of electrons and the second we add one more to the conductor one comes out the other end. With an electrical circuit the conductor goes from the source and returns to the source so when one electron leaves the source the conductor leaves one at the other side of the source.
With AC we are using a magnetic field to align those electrons first in one direction and then 1/120 of a second we swap them 180 degrees in the other direction. Again this conductor is made of atoms which is full of electrons and once the circuit is closed one electron enters the path and one leaves the path. When we have 6.25 times 10 carried to the sixteenth power of these electrons passing a point for a period of one second we have one amp of current flowing.
This generated AC current flows from the generator to the primary coils of a transformer and back to the generator. Magnetic induction then creates an AC current in the secondary of the transformer that then goes through our electrical systems and back to the secondary of the transformer.
It doesn’t matter if we are working with a battery (DC) or if we are working with our single phase panels in our home (AC), every electron that leaves the source must be replaced by an electron to that source. This is accomplished by the conductors; we must always have two connected to the load, one supplying and one returning. Break either one and current stops flowing. Yes just like salmon they must go home.
With our 120/240 volt single phase panels in our homes we have one 240 volt phase to work with. With a two cell flashlight we have one 3 volt source to work with. With the flashlight if one needed to one could center tap the two cells and use one battery for a volt and a half. With our homes we take a center tap from the single 240 volt source so we can use 120 volts. In our homes this center tap is connected to earth. When we take a voltage reading we will be reading what the voltage potential is above earth. From one side of the transformer to the center tap we will read ~120 volts above earths potential and should we read from both ends of the source we will see a potential of ~240 volts above earths potential.
The utility company also connects this center tap to earth as well as their high voltage grounded (neutral) conductor. This is easy to see with a pole mounted transformer as the copper conductor will be run down the side of the pole. The utility as well as the electrician connects to earth for four reasons and for these four reasons only. It has nothing to do with neither how safe the system will be nor how the system works. The four reasons are as follows; 1) lightning, 2) line surges which can be caused by lightning several hundred miles away or the switching of grids, 3) unintentional contact with higher voltage lines, notice that the higher the voltage the higher on the pole the conductors are, 4) and to keep everything stable under normal operation, remember that earth is nothing more than a big magnet and solar flares caused those magnetic lines to bend just as in a generator.
If we use the standard set by the NEC we can see just how much current will flow through an earth electrode such as ground rods. We shall connect from a 15 amp breaker directly to an eight foot rod. Using ohm’s law we would divide the resistance into the voltage; 120 volts divided by 25 ohms will equal 4.8 amps. This is not enough current to cause the 15 amp breaker to trip.
Now let’s use the unintentional contact when an ice storm causes the high voltage line to break and fall across our service drop. On average the voltage on the primary side of the transformer is 7200 volts. 7200 divided by 25 equals 288 amps. Let’s take a 200 amp service at 240 volts and if it were loaded to 200 amps it would be drawing about 48000 watts. 48000 watts divided by 7200 volts will equate to about 6.6 amps and most transformers that supply only one home will be protected by a five amp fuse which will open quickly at 288 amps of load.
[FONT=Times New Roman]When the voltage or amount of pressure gets high enough to push current through earth back to the secondary side of the transformer the fuse at the transformer will open protecting our electrical systems. The connection to earth has nothing to do with how our systems operate. It is the bonding of the equipment grounding conductor of our branch circuits to the neutral of our service equipment that affords safety to our systems but when we start bonding these at different places in the system we are causing problems instead of hindering them. [/FONT]
My concern was to make sure members really know the difference between Grounding and Bonding. The original post left me concerned that more clarification may be needed…however many have jumped in and have gotten very technical…again as a purist on G and B…just wanted to make sure the average member really knows the differences is all.
You are the man my friend
No No my friend…You are the Man! I just walk in the shadows;)
I’ve given up, it’s too frustrating. I very plainly asked about a floating neutral. Does that relate to grounding and bonding. yes. No I’m told that there is AC and DC. Really. wow. And the ping pong balls.
You know, never mind.
Think of this thread as a boat, rocketing toward the bottom of the ocean.
I look at “sub panels” the way Jeff Pope does, as just another receptacle. You wouldn’t bond the neutral and ground at a receptacle, would you? But again, I don’t know why. I would say its because the neutral is carrying a current and the ground normally isn’t. But don’t ask me.
Also, I find it absurd that some school that advertises that its courses are approved by InterNACHI for continuing education, won’t sell Kenton access to their courses because they view InterNACHI as a competitor. Kenton (our roofing expert) is just trying to learn more about electricity. In response, I’ve instructed our education department to make a list of all the courses they offer, to create our own mirrored but improved versions of all of them, to open them up to anyone for free, and to keep them free forever.
Paul, in-between our two post is the man. Did you read what he said, free