Can improper wiring actually cause a fire?

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snipped-for-privacy@spamcop.net wrote:

WHAAAAATTTTT????!!!!!!
Crawl back into your nice, warm, furry faraday cages! Or at least get a clue!
Sorry; couldn't resists; must .. not .. feed .. the .. trolls.. must .. not .. ...
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Pop` wrote:

Your posted email address doesn't seem to work.
Would you care to email your comments to me?
--

FF


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You didn't even get close with either statement. Want to try again?

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Not at all. To see this, one only has to look at AC skin depth. As frequency decreases, skin depth increases. At 60Hz, skin depth is approximately 1/3", deeper than common wiring is in diameter.

AC does not pass through a properly functioning capacitor. Current charges and discharges the plates, giving the appearance of electrons passing through the gap but at no time do they do so.

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CW wrote:

Are we not discussing different aspects of the phenomenon? Isn't skin depth the distance below the surface of the conductor at which the electric field strength drops to some fraction of what it is at the surface of the conductor?
That is not the location of the free electrons that carry the current. They stay on the surface.

Agreed that the electrons per se do not jump across the capacitor. But if you have alternating current on one side of the capacitor you will also have alternating current on the other side. In that (non?)sense the AC jumps across, though the actual electrons do not.
--

FF


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Backpedaling I see.

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CW wrote:

No, I am not.
You, however, seem to be unclear on the concept of skin depth.
Skin depth is a measure of the depth to which the electric field penetrates the material. It is not, as you seem to believe, the depth at which the current flows.
IOW, you're wrong.
--

FF


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snipped-for-privacy@spamcop.net wrote:

Speaking of unclear on the concept... an electric field is simply a field in which work is done on an electric charge -- IOW, where current flows.

You might want to grab yourself a high school physics text and [re]acquaint yourself with a few concepts before you so glibly assure CW that he's mistaken. First, it's *static* charge that resides on the surface of a conductor, *not* electric current. Second, the cloud of free electrons in a metal extends throughout it, rather than being confined to the surface.
Finally, you might want to ask yourself why the NEC-permitted ampacity of conductors below about 4/0 is [roughly] proportional to their cross-sectional area, not their diameter.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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Doug Miller wrote:

In a force field the potential to do work is present, whether work is actually being done or not. Surely you'll agree that the electric field extends beyond the wire into the surrounding air where no current flows.
You do not need current to have an electric field. Light is an example. The skin depth for light is real small.

Wikipedia has good articles on the subject.

OK, you got me there.
I wasn't familiar with the relationship between skin depth and current density. The current density at the center of #12 wire is almost 90% of that at the surface, right?
Last night I was thinking about this and remembered the Hall effect. That would not be possible without current passing through the conductor, rather than along the surface.
NOW, Mr CW can see me backpedaling.

The NEC tables make assumptions about heat-dissipation to the environment and 4/0 down to #8 conductors are typically multi-standed, both of which complicate the issue.
If we look at the DC resistances vs cross sectional areas for #10 and smaller in the table here:
http://en.wikipedia.org/wiki/American_wire_gauge
We see that the resistance is inversely proportionate to the the cross sectional area, confirming your point. In that same range the NEC permitted ampacity goes up on a per/ cross-sectional area basis as the wire size goes down, evidently because the larger surface to volume ratio dissipates heat better.
How about closing an AC circuit through a capacitor? Would you agree that the AC 'passes' through the capacitor even though the electrons do not?
BTW, other than the description at the top of the page, I don't see any difference between NEC 310-19 and NEC 310-18 here: http://www.houwire.com/products/technical/article310_18.html http://www.houwire.com/products/technical/article310_19.html
Are those pages correct?
--

FF


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snipped-for-privacy@spamcop.net wrote:

Yeah, I'll go along with that.

I haven't run the numbers, but that sounds about right, maybe on the low side, even. [snip]

In a sense, anyway -- but I think we're splitting hairs. Certainly if you apply an alternating current to one side of a capacitor, you get an alternating current out of the other side too.

I didn't check every entry, but the first one appears to be correct. The second one is definitely *not* correct: they have erroneously reproduced 310.18 under the heading of 310.19. The two tables are in fact substantially different.

--
Regards,
Doug Miller (alphageek at milmac dot com)
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On Sun, 31 Dec 2006 16:28:12 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:

The hair splitting is in how the phenomenon is described or measured, and it's easily confused by the base terms. In other words, the base term is "Alternating Current" which should describe voltage of a certain frequency.
In the capacitor scenario, the confusion arises because we tend to think of DC and its "flow of electrons." Obviously that flow must come to a stop at an open circuit, i.e. the capacitor. However, in AC, where the electrons only move a relatively short distance (and depending on frequency) before switching direction, the "effect" of electron flow is seen as being across the capacitor.
That "flow" is measured as current, which leads to the precept that AC flows through a capacitor and DC is blocked by it. In truth, however, although you can measure the current flow, and work is actually done, the electrons don't actually cross the capacitor.
--
LRod

Master Woodbutcher and seasoned termite
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On Sat, 30 Dec 2006 14:08:24 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:

Take a good look at a circuit board trace, if skin effect was a major problem most would behave similar to Windows 3.0
Mark (sixoneeight) = 618
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OP: Can improper wiring cause a fire.
Yes.
Next?
I do feel a bit vindicated watching these last 120+ posts about moot points, discussed by a group of full-time arguers, most of those don't have a clue. Now prior to my last run in with a few of these mental giants, I would have taken pleasure in throwing a few bones to these gnarly pups just to see them flip out all over each-other. Chasing tails, drooling, panting, refusing to roll over and LOTS of yapping.
Did anyone see that wicked chropractical move they did on Hussein's neck? I don't know why they bumped him off, he would have made a great commentator on FOX news.
*singing* "Lord loves a hanging that's why he gave us necks"
(Ren & Stimpy)
love,
r
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Did that a long time ago (sixoneeight) = 618
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snipped-for-privacy@fellspt.charm.net () wrote:

electrician or the homeowner.
That provision is in the Code explicitly to prohibit the use of junctions in which solder is the main, or only, thing holding them together.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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The only advantage to soldering house wiring is that expansion and contraction of the wires will not loosen the connection. I have seen one house done this way, it had been the home of an electrician (connection made with wire nut, remove nut solder wires, replace nut, tape with electrical tape, the heat shrink over the nut with RTV sealing the heat shrink). The wiring was also in conduit as is the practice in Chicago, though it could have been romex, being it was Mc Henry county. Definitely a belt and suspenders fellow. Remember to check the connection to your devices and tighten them up. (Not that I do as I say, except at the panel)
Mark (sixoneeight) = 618
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(sixoneeight)@hotmail wrote:

That's not an issue with properly made splices using wire nuts, either. If it were, the Code wouldn't permit them.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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On Mon, 18 Dec 2006 15:50:49 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:

Where in my story did you extrapolate that from.
If the wiring was done during the copper shortage in the 70's with aluminum wire it is a major issue.
Code allowed the use of the aluminum wire too.
Mark (sixoneeight) = 618
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(sixoneeight)@hotmail wrote:

From your reference to avoiding that issue being an "advantage to soldering house wiring".

Only if it was installed improperly. Note, also, that solder wouldn't fix *that* problem...

You should be using the present tense, not the past: Code still does allow the use of aluminum wire. Properly installed aluminum wiring is not hazardous. The problem is that installing it properly is not nearly so easy as installing copper wiring properly. Aluminum wire installed using the same materials and techniques used for copper is dangerous as hell, but aluminum installed using materials and techniques that are appropriate and approved for aluminum is safe enough to satisfy the NFPA.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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On Mon, 18 Dec 2006 16:42:00 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:

Given that most home owners do not know that it also must be maintained over "properly installed". A subdivision in Schaumburg Illinois has an much high than average electrical fire problem due to "properly installed" aluminum wire, so much so that insurers insist that the houses be rewired with copper before a new owner can get insurance or a mortgage.
It is hazardous to the bankers and insurance companies, and Cook county and Chicago no longer allow it for residences. But they still require conduit and wire nuts too.
Chicago the most grounded city in the states.
Mark (sixoneeight) = 618
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