# How does the typical mains power connect in the USA anyway?

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• posted on November 18, 2013, 1:42 am
Here is a picture of the incoming wires to my main circuit breaker:
http://farm3.staticflickr.com/2886/10915925156_0e21cf1404_o.gif
If we follow those three wires *back* to the nearest transformer, what do they look like (in terms of phase relationship to each other)?
If we follow those three wires *forward* to the first circuit breaker, what do they look like (in terms of connection to the literal earth of the ground)?
Note: This question is an offshoot of a 220v dryer question; but this question is asked to get to the root of *what* it is that is entering the house in the first place.

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<%-name%>
• posted on November 18, 2013, 2:14 am
Danny D'Amico wrote:

Hmmm, Your question has been answered more than once throughout this thread. If still did not get it. You really ought to follow the wires upto the main breaker panel. One note: Gnd and Neutral is connected together but they are not same in functionality in the circuit.

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<%-name%>
• posted on November 18, 2013, 2:44 am
On Mon, 18 Nov 2013 01:42:15 +0000 (UTC), Danny D'Amico

?? They're wires. It looks the same.

It's wires. It looks the same.

The same as it does at the transformer and the dryer.

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<%-name%>
• posted on November 18, 2013, 2:56 am
Danny D'Amico wrote:

Hi, How is your house electric system grounded? I still think your dryer is not grounded well. Measure between the dryer chassis(body) and ground point in Ohm scale on your meter. Do you read zero Ohm or fraction of Ohm? Also you should read zero Ohm between gnd(dryer body) and neutral on your dryer.
If it is all OK, some one else mentioned heating element sagging when hot rubbing on the dryer chassis not enough to kick the breaker but give spark and shock specially when hand is moist(doing washing)
I think this thread is coming to an end.

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<%-name%>
• posted on November 18, 2013, 7:22 am
This web page won't put up my posts if they're more than about 10 or 15 lines long.
Danny:
In the following e-mail address, each letter has been replaced with the letter or symbol to the right of it on a standard Qwerty keyboard.
If you can e-mail me, I'll send you a write-up that answers your question on what goes on both upstream and downstream of your electrical panel.
m l r ; r n s u # o ; p d / m r y
Leave out the spaces and type the letters to the left of the ones shown above to get my correct e-mail address. I put spaces in because if you type the letters r and n without a space between them, it looks like an m, and for this to work, the e-mail address you type has to be exactly correct.
So far as an electrical spark inside the dryer goes, I would look for any wires inside the dryer that are rubbing against the rotating dryer drum. In time, the drum will rub it's way through the insulation, and contact the copper conductor. Then, depending on WHICH wire is rubbing against the drum, you can get a shock from the dryer by touching the drum while it's running, or only when the heating element is heating, or only during the Permanent Press cool down cycle, or whatever. I'd at least make sure that no wires are touching the rotating drum.
--
nestork

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<%-name%>
• posted on November 18, 2013, 1:50 pm
On Monday, November 18, 2013 2:22:35 AM UTC-5, nestork wrote:

Good grief. What's next, NSA level encryption?

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<%-name%>
• posted on November 18, 2013, 2:39 pm
I hate to display ignorance, and I know I should know this.
But maybe somebody can explain.
The power lines are 3 phase, meaning they're 120 degrees out of phase to ea ch other allowing 3 wires to carry what 6 wires should (since they're gener ated by 3 sets of coils at the power plant).
The house is fed by just one of these wires, through a center tap transform er. That transformer sends 3 wires to the house: Neutral, +120 volts, -12 0 volts. Connect the two hots and you get 240, connect either hot to the n eutral and you get 120. Your safety ground is bonded to the neutral and so you should also have 120 from any hot wire to the ground. Neutral is the center tap.
Here's what I'm not getting at the moment. What are the connections to tha t transformer? If it is 3 phase leg to neutral on the primary side, then t he center tap should be above neutral on the secondary (house) side, right? Which would mean that house neutral is NOT at ground level. But I'm pret ty sure it is.

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<%-name%>
• posted on November 18, 2013, 2:48 pm
On Monday, November 18, 2013 9:39:55 AM UTC-5, TimR wrote:

each other allowing 3 wires to carry what 6 wires should (since they're gen erated by 3 sets of coils at the power plant).

The 6 vs three makes no sense.

rmer. That transformer sends 3 wires to the house: Neutral, +120 volts, - 120 volts. Connect the two hots and you get 240, connect either hot to the neutral and you get 120. Your safety ground is bonded to the neutral and so you should also have 120 from any hot wire to the ground. Neutral is th e center tap.

hat transformer? If it is 3 phase leg to neutral on the primary side, then the center tap should be above neutral on the secondary (house) side, righ t? Which would mean that house neutral is NOT at ground level. But I'm pr etty sure it is.
All the neutrals are tied to ground. Why would you expect the neutral on the secondary to not be at ground level? In the strictist sense, if you take a center tap transformer, the secondary side doesn't have to have any relationship to the potential on the primary side. It's can be completely seperate, it's a seperate winding not connected to the primary. What and how you hook it up determines what level anything is referenced to. In the power transformer case, the center tap (neutral) is tied to ground.

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<%-name%>
• posted on November 18, 2013, 3:08 pm
On Monday, November 18, 2013 9:48:27 AM UTC-5, snipped-for-privacy@optonline.net wrote:

that transformer? If it is 3 phase leg to neutral on the primary side, th en the center tap should be above neutral on the secondary (house) side, ri ght? Which would mean that house neutral is NOT at ground level. But I'm pretty sure it is.

Well, you're not seeing the problem. I wish I could draw here.
Your transformer has two wires going in, and three going out.
I don't know what primary is in my neighbor hood, let's say 2400 vac for an example. Which two wires do we use? You only have the choice of leg to l eg, or leg to neutral.
Choose leg to neutral: use a 10 to 1 turns ratio, your secondary will be 2 40 volts line to line. Then center tap it, and you get 120 from each line to center.
BUT: why would center tap be anywhere near neutral?
Choose leg to leg: does the same problem exist?
Once it gets into the house I understand how it works, but on the pole I'm hazy.
By the way you are dead wrong on the 6 wires thing. That part I do remembe r.

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<%-name%>
• posted on November 18, 2013, 4:37 pm
On 11/18/2013 9:08 AM, TimR wrote:

The secondary centertap is the "neutral" because it carries the imballance of the current in the secondary hot wires - the ends of the 240V winding. That is a common definition of a "neutral".
The secondary has no relationship to the primary, it is isolated from the primary.
The secondary relationship to earth depends on how the secondary is connected. The "neutral" (centertap) is earthed at the transformer. The neutral is then also earthed at the building. That limits the maximum voltage in the building with respect to the earth.

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<%-name%>
• posted on November 18, 2013, 5:09 pm
This web site explains it fairly well:
http://tinyurl.com/y4syno6
--
nestork

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<%-name%>
• posted on November 18, 2013, 5:21 pm
On Monday, November 18, 2013 10:08:23 AM UTC-5, TimR wrote:
:

to that transformer? If it is 3 phase leg to neutral on the primary side, then the center tap should be above neutral on the secondary (house) side, right? Which would mean that house neutral is NOT at ground level. But I' m pretty sure it is.

an example. Which two wires do we use? You only have the choice of leg to leg, or leg to neutral.

It's one of the 3 primary phases to primary neutral.

240 volts line to line. Then center tap it, and you get 120 from each lin e to center.

The center tap has no relation in terms of potential difference to anything other than the two ends of the secondary, until you connect it to something. The center is called the neutral and as part of the installation, it's run to the house and also tied to ground. Now the neutral of the transformer is at the same potential as ground.

m hazy.

ber.
You would go from 6 wires to 3 wires in a distributions system if and only if you were to consider the 6 wire system as the only other alternative to deliver power. That is that you have fixed in stone that you're to have a generator with 3 windings, delivering 3 phases via 6 wires to the load. Of course if you start with that, then a balanced 3 phase load reduces the wires in half.
But that isn't the real world. No one would do it that way to begin with. There are other alternatives and even a single phase system can deliver the same power without 2X the wires. 3 phase does use less copper and is better for other reasons as well. But it's not a miracle. The current carrying capability of the conductors is what it is and 3 wires can't suddenly carry the same current as 6. As i recall, the reduction in copper you get with 3 phase is around 25%.

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<%-name%>
• posted on November 18, 2013, 7:01 pm
wrote:

Pick one. It doesn't matter.

Because that's how it's wired. You *DEFINED* it as being 0V and connected it to ground.

No. There is no problem. Remember that transformers isolate. The secondary can be at any voltage you desire it to be, regardless of the primary (within the breakdown limits of the transformer, obviously). You connected one of it's secondary terminals to ground, defining that as 0V. Everything else falls out from there. You could have connected it to 1000V, but that wouldn't be smart. ;-)

There isn't any difference how it's connected there. You may have heard of "Delta" or "Wye" connections. Delta, connects the primary of the transformer between phases. A "Wye" connection would be from phase to ground. In the US, almost all loads are connected as "Wyes" and generators as "Deltas". I'm sure there are exceptions but that's what you'll find on your pole.

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<%-name%>
• posted on November 18, 2013, 9:39 pm
On Monday, November 18, 2013 2:01:42 PM UTC-5, snipped-for-privacy@attt.bizz wrote:

e:

to that transformer? If it is 3 phase leg to neutral on the primary side, then the center tap should be above neutral on the secondary (house) side, right? Which would mean that house neutral is NOT at ground level. But I 'm pretty sure it is.

an example. Which two wires do we use? You only have the choice of leg t o leg, or leg to neutral.

e 240 volts line to line. Then center tap it, and you get 120 from each li ne to center.

'm hazy.

mber.

So you too believe that the same amount of power that's delivered by 3 wire s with 3 phase would require 6 wires, twice the amount of copper to deliver any other way?
Remember when you insisted that it was illegal for employers to help pay for their employees Obamacare? Made an ass out of you on that one.
Remember when you didn't know the difference between how a 4 wire oven and a 3 wire is hooked up? Even with RBM, Bud and I all telling you that you were wrong. Made an ass of you on that one too.
And now we have your insistence that the two legs of a 240V service are not 180 deg out of phase. That no such usage of the wording would ever be used in engineering.
Well, here it is, from the IEEE. A paper delivered at a conference for power systems engineers:
Distribution engineers have treated the standard "singlephase" distribution transformer connection as single phase because from the primary side of th e transformer these connections are single phase and in the case of standar d rural distribution single phase line to ground. However, with the advent of detailed circuit modeling we are beginning to see distribution modeling and analysis being accomplished past the transformer to the secondary. Whic h now brings into focus the reality that standard 120/240 secondary systems are not single phase line to ground systems, instead they are three wire s ystems with two phases and one ground wires. Further, the standard 120/240 secondary is different from the two phase primary system in that the second ary phases are separated by 180 degrees instead of three phases separated b y 120 degrees.
There it is folks, in context, about the very specific point that krw claims is a lie.
Here's the essential cliff notes version, just for you krw:
"Which now brings into focus the reality that standard 120/240 secondary sy stems are not single phase line to ground systems, instead they are three w ire systems with two phases and one ground wires."
That's from an engineering paper presented at an IEEE conference. I suppose they are all idiots, liars, etc too, because they recognize that you have two phases that are 180 deg apart.
But keep digging your fools hole deeper if you like.

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<%-name%>
• posted on November 18, 2013, 11:04 pm
On Mon, 18 Nov 2013 13:39:26 -0800 (PST), " snipped-for-privacy@optonline.net"

<snipped more of the lying sack of shit's lies>

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<%-name%>
• posted on November 18, 2013, 6:54 pm
wrote:

Yes.

Kinda sorta.

Yes.

Well... There are two AC wires that are opposite, yes. If you said they were +120wt and -120wt, you would have a point (w being the angular frequency, or 2*Pi*f and t=time).

Yes.

Assuming no faults and ideal wires, sure.

Yes. ...which is grounded.

Yes. Almost always, though it really doesn't matter.

No. The center tap is grounded at both the transformer and the entrance panel. It *is* ground.

It is. I don't see your problem. You described things pretty well.

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<%-name%>
• posted on November 18, 2013, 7:11 pm
On Monday, November 18, 2013 1:54:55 PM UTC-5, snipped-for-privacy@attt.bizz wrote:

And if you said they were 180 different in phase from each other, relative to the neutral, you would also be correct.
KRW only understands opposites, not phase.

Yes because the two hots are 180 deg out of phase with each other. If they weren't you wouldn't get 240V

The center tap is by definition the neutral. Connecting it to ground ties it to ground potential. It's like if you had a battery in your hand, and someone saying the negative terminal is above earth/ground potential. It makes no sense. It has no realtion to anything when it's not hooked up to anything. Hook the neg end of the battery to ground and now that end is at ground potential.

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<%-name%>
• posted on November 18, 2013, 9:36 pm
Thanks everybody, that was very helpful.

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<%-name%>
• posted on November 18, 2013, 9:52 pm
On Mon, 18 Nov 2013 11:11:06 -0800 (PST), " snipped-for-privacy@optonline.net"

Wrong.

No, unlike the stupid lying ass, Trader, I know the difference. <more lies snipped>

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<%-name%>
• posted on November 18, 2013, 10:36 pm
On Monday, November 18, 2013 4:52:51 PM UTC-5, snipped-for-privacy@attt.bizz wrote:

Here, so everyone can see who's a liar and who knows what they are talking about. From the IEEE (Institute of Electrical and Electronic Engineers), a paper delivered at a rural electric power conference:
"Distribution engineers have treated the standard "singlephase" distributio n transformer connection as single phase because from the primary side of t he transformer these connections are single phase and in the case of standa rd rural distribution single phase line to ground. However, with the advent of detailed circuit modeling we are beginning to see distribution modeling and analysis being accomplished past the transformer to the secondary. Whi ch now brings into focus the reality that standard 120/240 secondary system s are not single phase line to ground systems, instead they are three wire systems with two phases and one ground wires. Further, the standard 120/240 secondary is different from the two phase primary system in that the secon dary phases are separated by 180 degrees instead of three phases separated by 120 degrees. "
Anyone following the discussion can read it and see that the IEEE engineers are saying EXACTLY what I've been saying all along. It couldn't be any more specific and on point. That IEEE paper is 100% in agreement with everything I've said. Of course krw will snip it and ignore it, instead of learning.