Originally Posted By: gromicko This post was automatically imported from our archived forum.
Joe Farsetta and I are collaborating on an online electrical course for home inspectors… well actually Joe is doing all the work, I’m just putting together the technical layout. It is designed to walk a home inspector through the electrical portion of a home inspection.
Anyway, I'm worried that the resolution I'm using 499 X 499 pixels isn't good enough. Click the pic below and let me know if you agree that I will have to trade speed for resolution.
Originally Posted By: dverge This post was automatically imported from our archived forum.
Hi Nick; Any idea when the online course might be ready? How long will it take to complete the course? Can it be done in segments? Will there be education credits earned?
Originally Posted By: jfarsetta This post was automatically imported from our archived forum.
Dave,
The course is prety much finshed. Its pretty good, and starts with the discovery of electricity by the Greeks. It progresses through some basic physics, including why some thngs are conductors, while others are insulators. It explains Ohms law, and parallel circuits. It speaks to electrcal panels, sine waves, alternating current, and junction boxes. I think its abut 65 pages long. My head really hurts 
It includes some info on Federal Pacific, and aluminm wiring. It steps a newbie through some of the things to look for durng an inspection. It has a photo segment, which is not in any way supposed to be more than a training excersise in some of the more typical stuff to look for. It contans a checklist outline, a glossary, and a short quiz at the end.
It also speaks to common safety practices.
The bottom line is that this course in no way teaches you everything you need to know. It was developed to fill a void we have. That is, there is no way to stop an unqualified person from performing an inspection. That being said, it is important to try and provide a good foundation of knowledge from which to build. It's purpose is also to get folks THINKING. This, above all else, is the most critical. Everythng needed to be known to be a competent inspector will not come out of a magic box, an instrument, or a textbook. It is acquired knowledge, attained from a variety of means.
It is the first in a series I am writng for Nick. Ths one is open to all. The idea is offer all subsequent on-line courses to NACHI members only. It is not an advanced course, so dont jump all over me. Realize who the target audience is intended to be. If nothing else, the physics and electrical theory portions are interesting, and some of the info may be helpful to all. My own theory is that if you can visualize how something works, and why things happen, you can apply that theory in the inspection process. It helps you to be sharper,and assists you in UNDERSTANDING how things work, and why things can fail. This equates to closer examination of items.
For instance....
An electron is like a pool ball. One ball smacks another, and sends it on its way. Most of the energy transferrs from one ball to the next. Hence, ball#1 stops moving, and ball #2 starts moving. However, some energy is lost in the transfer. In the movement of electrons, what does this lost energy manifest itself as?
Answer, anyone?
Now, think about a #14 wire, conected to a 20amp breaker. Visualize what is going on...
-- Joe Farsetta
Illigitimi Non Carborundum
"Dont let the bastards grind you down..."
Originally Posted By: phinsperger This post was automatically imported from our archived forum.
1) Most of the energy transfer is kenetic to the second ball as joe said.
2) The next amount of energy goes into sound. The smack you hear as the balls hit.
3) The smallest amount of the energy goes in to heat. Friction of the balls on the table, the compression of atoms in the balls as they transfer kentic energy.
Originally Posted By: dvalley This post was automatically imported from our archived forum.
Quote:
Answer, anyone?
Kevin is absolutely correct-o-mungo.
Some of the cue ball's energy was lost to heat when it struck the stationary ball. Some energy is lost in the transfer when one electron strikes another.
Joe also stated...
Quote:
Now, think about a #14 wire, connected to a 20amp breaker. Visualize what is going on...
That's exactly why a wire heats when current flows through it. If too much current flows through a wire (and the breaker is over-fused) overheating will damage the wire, melt the insulation and possibly become a fire hazard.
Originally Posted By: jfarsetta This post was automatically imported from our archived forum.
Okay.
Good answers, and all correct. But, we are experienced nspectors, and much of this is second nature to us. Many are good at understanding how things work, but not WHY.
Then we have Ncky Newguy. Not knocking him, just trying to help him with some of the why's. If they start understanding some of this stuff, they can start to refine their electrical inspection techniques.
The course is designed to provide some basic information. For instance, why does current increase in a household circuit, as the 2nd, 3rd, and 4th lamps (let's say) are turned on?
Okay...
OR THIS ONE:
If a #14 wire had, say 1000 amperes pumped through it, as opposed to, lets say, 240 volts at 30 amps, under a continuous load, not overloading the breaker... Now, picture both cables stapled to a wooden joist. Which would do the most damage, do you suppose, and why?
Okay.... go for it.
-- Joe Farsetta
Illigitimi Non Carborundum
"Dont let the bastards grind you down..."
Originally Posted By: jfarsetta This post was automatically imported from our archived forum.
Todd,
Correct answer. Actually, copper melts at approximately 250 degrees Celcius. In the mean time, with 30 amps grinding through it, everything around that conductor would have burned, whereas the flash would have smoked the conductor right away. Nice one.
But what about the 1st question?
-- Joe Farsetta
Illigitimi Non Carborundum
"Dont let the bastards grind you down..."
Originally Posted By: dvalley This post was automatically imported from our archived forum.
Quote:
But what about the 1st question?
why does current increase in a household circuit, as the 2nd, 3rd, and 4th lamps (let's say) are turned on?
Turning on more lamps in the same circuit increases the voltage and will make more current flow. Current then increases and gets stronger due to more electrons being in motion through a single circuit.
This is where wire sizes and breakers are put through their test.
Originally Posted By: jfarsetta This post was automatically imported from our archived forum.
Incorrect!
Receptacles are wired in parallel. In fact, the entire house is one giant parallal circuit.
Now, every device plugged in has some resistive factor. In parallel circuits, each device added actually REDUCES the resistance of the circuit.
As an example, if a lamp has a resistive valus of 4 ohms, and a second lamp is turned on, in that same circuit, and it also has a value of 4 ohms, then te resistance of the circuit becomes 2 ohms.
The voltage remains CONSTANT at 120 volts.
Ohm's law tells us that if voltave remains constant, and resistance decreass, then current INCREASES.
If you start thinking about this, yu can really begin to understand how breakers relate to each other, and how the panelboard functions. More importantly, WHY homes are wired this way, and how overloads occurr.
This is some of the stuff contaned in the course.
Does anyone know what a valance electron is? 
-- Joe Farsetta
Illigitimi Non Carborundum
"Dont let the bastards grind you down..."
Originally Posted By: jcockerel This post was automatically imported from our archived forum.
In simple terms, valance electrons are the outer most, highest energy level electrons, but it is the outer most sublevel, which holds the valance electrons, and the number of these electrons changes with the transition elements. I will attempt to explain below without going into too much detail. Periodic law, or the manner in which the periodic table is laid out, defines each new row as beginning to add electrons to a different energy level, beginning at the K shell, then going to the L shell and so on. Frequently these levels are numerically indicated as 1, 2, 3, etc. Level 1 only allows at most 2 electrons; level 2 allows 8 electrons, distributed into 2 sub-levels, one containing 2 electrons in a s-sublevel and the other containing 6 electrons in a p-sublevel. In level 3 beginning with the element Na, there are 18 electrons allowed, but one of the sublevels of this level does not begin getting filled until after the element Ca, which has two electrons in its 4th level. This 3d sublevel can hold 10 electrons, and these elements begin the transition series of elements. The additional valance electrons come from the fact that the 3-d sublevel is actually at a slightly higher energy level than the 4-s sublevel. Therefore with the transition elements, the outermost energy sublevel can hold 10 electrons. A completely filled 4th level can hold 32 electrons, and the 5th level can hold 50. Because the electrons in the highest energy level (the ones furthermost away from the nucleus are the valance electrons, the transition elements frequently have valances such up to +3, such as Fe.
Originally Posted By: jfarsetta This post was automatically imported from our archived forum.
Great explanation, though way above what an average HI knows. I was hopng for a simpler explanation, with the impact beng that the more valence electrons, the better the conductor. Copper, for example, has more valence electrons whan, say, wood
This explains the relationships between insulators, semi-conductors, and conductors.
-- Joe Farsetta
Illigitimi Non Carborundum
"Dont let the bastards grind you down..."
Originally Posted By: phinsperger This post was automatically imported from our archived forum.
and the atom of choice to do this to is hydrogen as it is the simplest atom. Cold fusion is a topic that is widely debated even by people who actually know this stuff.
