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

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On Saturday, November 16, 2013 6:20:01 PM UTC-5, snipped-for-privacy@attt.bizz wrote:

And those two legs are in fact 180 deg out of phase with each other. That is the statement you disagree with, but it's true. Hook up a scope and look.

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On Saturday, November 16, 2013 4:28:26 PM UTC-5, Mark Lloyd wrote:

I agree. They are hung up on the fact that in an electrical power distribution system, it isn't referred to as two phase. But it is called "split phase", and when you split something, well it seems you wind up with more than just one.
I would not call the electrical service two phase, as I think someone here might have, but in fact you do have two AC waveforms present that are 180 deg out of phase with each other.
You could make the more general case of a "box" that you put a sine wave into and get various sine waves out of. They can each be described in terms of their frequency, amplitude, and phase relationships to the original and each other. You could have one, two, three, 10 different phases, all derived from one input. Are they going to say that if one of them is 180 deg out of phase with the input, that it's not correct to say that? You can only call it the "opposite"? Good grief!

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On 11/16/2013 3:28 PM, Mark Lloyd wrote:

http://en.wikipedia.org/wiki/Split_phase "A split-phase electricity distribution system is a three-wire single-phase distribution system."
Everyone working with power will call this a single-phase system.
Talking about 2 phases tends to confuse things. People working with power are not likely to talk about 2 phases in what is clearly a single phase system. I have most often heard the 2 different hots referred to as "legs".
A "phase" that is always simply the negative of the other "phase" (the same as 180 degrees out of phase) is meaningless.
Talking about phase relationships is entirely reasonable.

There is a specifically defined 2-phase system. It is not 180 degrees apart.
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On Sunday, November 17, 2013 1:16:58 PM UTC-5, bud-- wrote:

You left out what follows:
"The two halves are 180 degrees apart with respect to center point."

It's also split phase. When you split something, do you still only have one? Cite me an example.

Only if you don't understand the issues.
People working with

It's no more meaningless than a phase difference of 120 deg, 90 deg or any other difference. It is what it is. If you didn't have a 180 deg difference, you couldn't support 120V and 240V with those 3 wires.

And that was what started this when it was stated that the two hots on a 240V circuit have a 180 deg phase difference. It of course is true. You can hook up a scope and see it. But KRW insists that it can't be called a 180 deg phase difference, it has to be called "opposite", which makes no sense.

I agree with that. But again, the post that started all this did not call it a "2 phase system". The observation was simply made that the two hots in a 240V connection are 180 deg out of phase with each other. Actually, I think the poster made the error of saying they were 120 deg apart, but that was quickly corrected.
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No, it's not meaningless. That's what it is. It's off the opposite side of the transformer so *is* a negative.

When there is a phase relationship, it is. In the case of an Edison connection there isn't, between the two legs. They're opposites. If you cut the power to the transformer, both legs will disappear together. There will not be a pi difference. If there is a line distortion, it will appear at the SAME time on both legs, but opposite WRT each other. There will not be a phase difference. Saying there is, is often slang but it just adds confusion, as you point out.
Saying that there are two phases (in an Edison circuit) confuses the issue completely. There simply aren't. There is a reason they're known as "legs", not "phases".

Right. The only useful two-phase system I've seen has them 90degrees apart.
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On Sun, 17 Nov 2013 16:28:22 -0800 (PST), " snipped-for-privacy@optonline.net"

<no more time wasted on the pretend engineer>
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On Sat, 16 Nov 2013 10:50:51 -0800, snipped-for-privacy@optonline.net wrote:

I'm pretty sure I learned, long ago, that they're 120 degrees out of phase with each other.
The reason, IIRC, has to do with the fact that they generate electricity with three coils. And *those* three coils are wound symmetrically (i.e., in a Y or delta) which makes them 120 degrees out of sync.
So, each of the three wires coming out of the power company (which are the three wires on the poles along the street) are 120 degrees out of sync (if I'm correct).
You only get *two* of those wires going into your house. But they're still 120 degrees out of sync (AFAIK).
Besides, if they were 180 degrees out of sync, what would the third wire be on that pole?
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On Sat, 16 Nov 2013 20:04:33 +0000 (UTC), Danny D'Amico

Nope. If you must assign a phase relationship (though it's technically wrong) it would be 180 degrees. The phases in a three-phase system are 120 degrees apart. Remember, a circle is 360 degrees (what happened to metric?).

Yes, the generators are three-phase, as is the distribution system.

So far, so good.

Nope, you only get one, and that one is split in half, using a center-tapped transformer (center goes to ground/neutral).

You only see one of the three. Your neighbor might be 120degrees from you (on another leg of the three phases) but you can't see that.
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On Sat, 16 Nov 2013 17:58:35 -0500, krw wrote:

I was always told that base 60 allowed the Babylonians to divide by the most numbers (1,2,3,4,5,6).
As I understand it, the Babylonians created the 360 degree circle by starting from pie sections.
BASE 16 didn't work for them: a) If you split a pie in half (vertically), you get 2 parts. b) If you split that in half (horizontally), you get 4 parts. c) If you split that yet again in half (with an "X") you get 8 parts. d) If you keep doing that, you get 16 parts e) This goes on depending on when you want to stop.
16 is dividable by 1,2,&4.
But, if you split into 12 parts instead of 16, you can now divide by more things, i.e., you can divide 12 by 1,2,3,4,&6.
If you keep dividing, your 12 becomes 60, and now you can divide by 1,2,3,4,5,&6 (and a few more).
So, the clock, I'm told, became 12 hours and 60 minutes.
How that 60 minutes multiplied by 6 to 360 degrees, I'm told, is just a matter of having better granularity.
So, if I understand what I really didn't understand, base 60 was merely more dividable by things than any other base the Babylonians could come up with.
But, I could be wrong because they came up with the Metric system for a reason ...
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On Mon, 18 Nov 2013 02:16:18 +0000 (UTC), Danny D'Amico

OMG! I thought it was only the US that used a non-French system!

Pi sections? No, it was because 12 (hours), 60(minutes), and 360(degrees) are such a beautiful numbers. They have so many factors.

Where did that come from?

Yep. It's a beautiful number.

Sure, but Pi had nothing to do with it.

A good reason but like anything French, it's certainly not perfect.
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On Thu, 14 Nov 2013 16:47:47 -0500, Ralph Mowery wrote:

I'm not sure HOW static electricity could build up, but, that's the only thing, at the moment, that makes sense to me.
Here's a picture of what the vent hose looks like when it's all in place:
http://farm4.staticflickr.com/3815/10862854513_17c2fe362f_o.gif
Here's a front view:
http://farm4.staticflickr.com/3833/10862855523_8f2c472367_o.gif
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On 11-14-2013, 20:27, Danny D'Amico wrote:

If it only happens when you turn it on, it wouldn't be static build up. That would have dissipated while it was off.
I'm wondering about some kind of misalignment or wearing out in a two-pole switch. If one side of the 240 is energized ten milliseconds before the other, AND that side is shorted to the shell, AND the shell is not grounded but the vent hose _is_, then this could happen.
And that would be dangerous, obviously. Call a pro. Happy Halloween.
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Wes Groleau

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On Thu, 14 Nov 2013 16:47:47 -0500, Ralph Mowery wrote:

Hmmm... There is no *external* 'strap" going to the steel frame of the dryer. Are you saying there should be an *internal* strap that I can look for?
http://farm4.staticflickr.com/3812/10862854943_3bf128caf4_o.gif
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This looks like a 3 wire power cord. You need to unplug the dryer and open up the back where the wire goes in. Look and there will be 3 terminals the power wire hooks to. It will probably be the middle wire that is the neutral and there should be a strap going from there to the frame of the dryer.
While the dryer is open look around for any black or burnt areas near wires or the internal electrical parts.
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On 11/14/2013 8:39 PM, Ralph Mowery wrote:

Three wire cord doesn't have a neutral. Two hots and a ground.
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Christopher A. Young
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Wrong! Two hots and a grounded conductor (neutral/white). These types of plugs are often referred as a 120/240. Meaning that it provides both voltages to the device. The new 4-wire plugs do the same thing, but have a dedicated grounding conductor for fault purposes.
As per code, a grounding conductor shall "never" carry any current unless a fault is present; and the only purpose for carrying this current is to trip the breaker. The other purpose of a grounding conductor is to equalize the potential of attached devices to ground, thereby reducing, but not eliminating, the risk of shock.
(it is possible that the service is 110/220)
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On Thu, 14 Nov 2013 20:39:41 -0500, Ralph Mowery wrote:

Does this look ok from where you sit?
http://farm6.staticflickr.com/5474/10879027305_17cb94ac7e_o.gif
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That green wire needs to be terminated on the center terminal. This will bond the dryer to ground (yes, the neutral). If there is a short you will find out pretty quick.
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I could not tell what the other end of that wire is doing, and assumed that it was not terminated. If, by chance, it is affixed someplace else, make a jumper wire that will go under that screw and terminate it on the center terminal.
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On 11/15/2013 10:05 PM, Danny D'Amico wrote:

Looks fine, on my web browser.
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