220V dryer sparked on startup (3 wire) What to test?

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On Tue, 19 Nov 2013 17:21:26 -0500, Ralph Mowery wrote:

I must apologize for repeatedly asserting that they were connected differently!
I was astounded when I followed the wires, for the first time, and saw this:
http://farm4.staticflickr.com/3713/10951553445_08698c037a_o.gif
Just as you said, we have thick wires and thin wires going to the same spot, and some are green, some are white, some are bare copper, and some are huge aluminum wires, some of which are themselves bare while others are white.
So, if I (finally?) understand it, all these (neutral & ground) wires connect at this one point in the breaker panel, and, from there, they go via that big bare copper wire into the ground (probably just below where the water comes in).
They *also* go straight down into the striped neutral wire which is connected to the nearest transformer.
And, since that neutral is hopefully a better ground, *most* of the current in that circuit will go into the striped black neutral wire.
Do I have it right yet?
Note: On purpose, I won't discuss what's happening between the house and the transformer, because I've read every post in the 180-degree inverted argument, and, well, I probably shouldn't have since they all just confused me to no end.
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On Tuesday, November 19, 2013 5:49:45 PM UTC-5, Danny D'Amico wrote:

Almost. Except the last part about the service neutral being a better ground. It's not that it's a better ground, it's not a ground at all. It's connected to the center tap of the transformer. Current comes out of one leg of the transformer, it's going back to either the other leg or the neutral/center tap.

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On Tuesday, November 19, 2013 5:49:45 PM UTC-5, Danny D'Amico wrote:

This link has an excellent description:
http://www.samlexamerica.com/support/documents/WhitePaper-120240VACSingleSplitPhaseandMultiWireBranchCircuits.pdf
I don't remember who first provided it here, but it covers the subject well.
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That bus bar is where the neutral/ground bond is made. Both grounds and neutrals may be terminated on this bus bar, regardless of size as long as the barrel of the lug they are being placed into supports the wire size. Your sub-panels might have something similar going on, and this is okay, as long as the bus bar is isolated from the metal of the panel enclosures. The bus bars should be on some sort of stand-off in the sub-panels.
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On Tue, 19 Nov 2013 20:40:16 -0600, Nightcrawler® wrote:

That's interesting. I'm trying to think why. I guess they want only one good ground?
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On 11/19/13 9:29 PM, Danny D'Amico wrote:

not just the path of least resistance.
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On Tue, 19 Nov 2013 21:36:55 -0600, Dean Hoffman wrote:

If the neutral bars were connected to the case at the sub panels, there might be resistance between the case of the sub panel and the ground of the main panel.
If there is resistance, there will be a potential.
If that's right, what they want is for the wire from the sub panel neutral bus to be the only connection to the main breaker neutral bus, so that they *know* it is a low resistance path.
Is that right?
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On 11/19/13 9:57 PM, Danny D'Amico wrote:

There will be a parallel circuit between the case of the sub panel and the case of the main panel. It will be in parallel with the hopefully low resistance neutral. A person touching the sub panel will become part of the parallel circuit. He probably won't even notice it if the neutral is ok. He could get a shock if the neutral is compromised for some reason. The code has a special section devoted to livestock buildings and equipment. Critters are grounded better than humans. They'll notice a bit of stray voltage where humans won't. I guess dairies are one place where it's important to keep stray voltage to a minimum. Milk production suffers if things aren't up to Hoyle.
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LOL! And the bubba wiring jobs...
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There is only one earth/ground to neutral connection allowed in a power distribution system unless a new service is established. The ground to neutral bond is only allowed at the point where the service is established. This would require a dedicated ground rod for the panel, and no sharing of grounds/hots/neutrals of other panels. Your meter-main is where the service to your residence is established, and that is where the earth/ground bond is made.
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On Tue, 19 Nov 2013 22:27:52 -0600, Nightcrawler® wrote:

I hadn't realized only one earth ground was allowed, and, that it had to be at the service entrance.
I would have thought the more grounds, the better.
So thanks for advising me on that.
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Maybe I did not write that correctly. You are only allowed to make one earth to neutral "bond" (termination) per service, and this shall be made at the point of service entry (meter-main). All circuits associated with this panel must return to this panel. Sub-panels are not "services", and there is "not" to be a earth to neutral "bond" at these locations. If bonded to ground at these locations, then the ground becomes a current carrying conductor that operates in parallel with the neutral.
As with the meter-main, all circuits that originate from the sub-panel must return to the sub-panel. However, you may install a ground rod for any sub-panel or device, as you wish, as long as it is installed via proper wiring methods and the complimentary earth ground shall not be bonded to the neutral unless the circuit originates from the service entry. A ground rod may be installed, a water pipe bond, a gas pipe or other earth bond may be made without returning to the panel as long as the connection to a device does not interfere with the proper wiring methods from said devices power supply. In industrial settings it is often found that a device will have a ground rod, or two, installed with a large gauge wire terminated on the metal frame of the device. This wire is not "electrically" connected, but is not necessarily isolated from the service ground, at the device, either. Though, sometimes it is.
Modern code requires two ground rods, anyway. You need to learn how to separate what a ground is, and what a neutral is, in your mind. A neutral conductor ideally does not carry current, but this is not an ideal world and it is almost impossible to wire a structure with a perfect balance, at all times, so there will be current on the neutral. Sort of why I think it is stupid that they allowed the "grounded conductor" (the neutral) to be called a neutral. It used to be called "the Common". Calling a current carrying conductor a neutral is like saying fire is water.
The only purpose of the ground wire is to provide a direct shunt path for the circuit breaker in case of a "hot" to chassis fault, and to perform what is called equalizing potential. Meaning that all exposed (even non-exposed) conductive surfaces have the same potential (voltage/charge). Works in theory, but anyone who has gotten a zap at a water faucet knows that systems may fail, after time.
Equalizing potential is the concept that it is not possible to induce electric flow between two points that have the same electric state. This includes static, DC, and AC electricity. Put two wires on the positive of you car battery and touch them together. What happens? Put two single pole circuit breakers in a panel, inline, left to right, sharing the same bus. Wire the breakers together and turn the breakers on. What happens? Get yourself on a high tension line (without getting zapped) and hand over hand along its length, staying 15'+ from any ground or opposing phase. What happens?
Stand next to a high tension tower, say one foot away and have the ground ring somehow fail for this tower. Take a step. What happens?
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On Wed, 20 Nov 2013 11:08:08 -0600, Nightcrawler® wrote:

In trying to better understand the "why" of this, I found on the net this really nice (I think) summary, with clear & obvious pictures:
http://www.hammerzone.com/archives/elect/panel/sub_panel/01/new.htm
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I already stated the "why of it". The ground wire is not supposed to carry current or voltage (be a part of a circuit). By bonding the neutral elsewhere you are making the ground system part of the neutral system going back to the meter-main. Part of the imbalanced current will flow through the neutral, another part will flow through the ground wire. This also will cause some nasty harmonics in your electrical system. A neutral is not allowed to be separated from the power conductors it serves, other than at the termination points, for this reason. Things like this may cause fires. Since the grounding system is not as direct as the power supply ( it may be branched and go almost anywhere) you will never know what kind of harmonics, powered ground loops and such you may create, and, as with neutrals, if you open up a connection in say, a junction box, and are expecting no voltage/current you will get a surprise. It is best just to accept things as they are and suffice it to say, "with good reason."
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On Wed, 20 Nov 2013 19:53:06 -0600, Nightcrawler® wrote:

That one sentence says a lot!
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On Wed, 20 Nov 2013 19:53:06 -0600, Nightcrawler® wrote:

This too is a very interesting observation. I was not aware of this togetherness requirement, but it makes sense.
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On Wed, 20 Nov 2013 19:53:06 -0600, Nightcrawler® wrote:

All these observations are nuggets of gold, in that it's not intuitive that the grounding system is more branched than the neutral system (which isn't branched); but it makes sense once you point it out.
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On Wed, 20 Nov 2013 11:08:08 -0600, Nightcrawler® wrote:

Nothing. No spark, anyway.

I'm not sure how the circuit breakers work because I saw A-B-A-B arrangements in this diagram, so, I know what answer you're looking for, but, I don't really understand how they wire circuit breakers.
http://farm8.staticflickr.com/7292/10955976554_054ba18de1_o.png

Same thing that happens to birds and squirrels. Nothing.

I'm not sure what a "ground ring" is, but, I assume you're saying the tower loses its grounding. But, the lines are insulated from the tower, so, I would think nothing happens - but - again - I'm not sure how it's wired up.
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That is not a Square D panel, but no matter. Not all panels are the same. With your panel it goes A-A, drops down a breaker and goes B-B. This is how you get both hot legs with the breakers that you have. In the example you provided, the circuit breaker would go all the way across the panel and would be rather complex inside for the thing to trip both legs. I have never seen a panel with this set up.

Most likely you would be dead. The static electricity that builds up on those things is so great that the difference in potential in just a few feet is close to what is strung overhead, and possibly more. Think around 100,000+ volts per meter, decreasing the further you are away from the tower. The only reason I brought this up is to emphasize the importance of equalizing potential, and that is one of the jobs of the grounding conductor and subsequent grounding methods within the system, and therefore why the grounding portion of an electrical system is its own entity and should be treated as such.
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On 11-20-2013, 21:12, Nightcrawler® wrote:

If the resistance through your shoe & sock, up your leg, down your other leg, and through your other shoe and sock is low enough compared to that through the earth between your feet, quite likely.
People HAVE died that way, but others have survived. With the right shoes, and enough moisture in the soil, you might not even feel it.
I'm not volunteering for the experiment.
--
Wes Groleau

People would have more leisure time if it weren't
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