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

I don't think it really matters whether we're calling the 120 VAC lines coming into our house "single phase power" or two separate phases. Or, precisely what to call it certainly doesn't warrant the amount of time being spent arguing over what to call it.
What matters is that we understand how the wiring in our houses (including the electrical panel) works, and I don't think that part was ever in question.
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nestork

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On Sunday, November 24, 2013 1:05:43 AM UTC-5, nestork wrote:

It does warrant a response when you have some people here saying that anyone that says the you have two legs, two phases, 180 deg out of phase, "know very little or just enough to confuse themselves". And the village idiot questioning my degree in electrical engineering. I take offense to that. I've provided a link to an IEEE peer reviewed paper presented at a conference of power engineers.
"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. Further, the standard 120 /240 secondary is different from the two phase primary system in that the s econdary phases are separated by 180 degrees instead of three phases separa ted by 120 degrees. "
That's from an unimpeachable source, the IEEE. I've also provided links to eqpt manufacturers, etc.
The other side, nothing but flapping gums.

That is correct. But when you start baseless personal attacks and are incapable of even defining the word "phase", then what do you expect?
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John, we all understand that, but since the two 120 VAC sine waves coming into the house are 180 degrees out of phase with each other, it's natural to think of it as two phase power. Maybe it's not, but thinking of it that way helps us understand our house's electrical panel and the wiring coming out of it, and that's really the goal for most DIY'ers.
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nestork

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On 11/23/2013 7:12 PM, snipped-for-privacy@optonline.net wrote:

"singlephase" distribution transformer connection as single phase because from the primary side of the transformer these connections are single phase and in the case of standard 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. Which 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 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 secondary phases are separated by 180 degrees instead of three phases separated by 120 degrees."

Aristotle says that 4,126 angels can dance on the head of a pin.
Confucious says that incoming power in the USA in the twenty first century will be single phase.
Jesus said if thy brother offend thee, and strike thee on the phase, turn the other cheek.
Billy Graham says he's getting old, but that does not phase me very much.
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Christopher A. Young
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On 11/23/13 4:37 PM, John G wrote:

Well, what we think of as single phase isn't. It's actually two phase. Trader 4 posted a link to an IEEE paper in another thread. Here: http://tinyurl.com/lpwq82z I work with irrigation which mostly relies on three phase power. We sometimes tap power off grain bin sites which many times have "single" phase 240. We'll use a transformer to produce 480 and add a phase converter for the third phase. The converter adds one phase to the two already there to run three phase motors. It never occurred to me to think of "single" phase as actually two phase until Trader posted the link. It has to be or phase converters wouldn't make our irrigation systems run. Granted, none of this probably matters to Joe Homeowner wiring a garage light or a stove.
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On Saturday, November 23, 2013 7:56:02 PM UTC-5, Dean Hoffman wrote:

r

Thank you. Good to see someone looked at the link and realizes what it says.
That link is from the highest credibility source you could possibly get, but aaddresses the very core of the issue:
"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. Further, the standard 120 /240 secondary is different from the two phase primary system in that the s econdary phases are separated by 180 degrees instead of three phases separa ted by 120 degrees."
I supplied other links to references from electrical eqpt manufacturers tha t clearly show and describe 2 phases, 180 deg out of phase with each other as well:
http://www.behlman.com/applications/AC%20basics.pdf
http://www.samlexamerica.com/support/documents/WhitePaper-120240VACSingleSp litPhaseandMultiWireBranchCircuits.pdf
So far, the other side has no references.

I'm still waiting for the definition of the meaning of phase from those that deny that the two hot legs on a split phase 240/120V service are 180 deg out of phase with each other. That is what started all this. They appear to be hung up on the fact that it's derived from a single primary phase. How it's derived doesn't change what you get, what you can see on a scope, how it drives a load, etc. You brought up an example of generating an additional phase via a transformer. Earlier I brought up another, very common example too, open delta three phase.
For most 3 phase loads, 3 transformers are used to step down from the primaries. They have 3 transformers, one connected to each of the 3 utility primary phases. So far, I think everyone agrees with that. Three phases in, three phases out. Now, for light 3 phase loads, to save the cost of an additional transformer, by using a center tap transformer, the utility can supply 3 PHASE POWER, using only two transformers, connected to only TWO of the utility primaries. The utility calls that 3 phase power. The customer calls it 3 phase, the 3 phase motors run on it, you can see 3 phases on a scope. Yet it's derived from only TWO of the utility primary phases. Two phases in, three phases out. Following the arguments of those on the other side, then that should only be called two phase power. Yet there it is, 3 phase.
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On 11/23/2013 5:37 PM, John G wrote:

Wish I could remember the details. And the people on this list are glad that I can't. But, I remember hearing one time, how the theologians of earlier generations used to write commentaries on this or that. Commentary on the parable of this or that. One theologian wrote a summation of the gospel, in such simple terms he figured it would be the do all and end all, of writings. Shortly after he published it, a lot of people wrote commen- taries on his summary.
Nestork did excellent job of shutting down the thread, and then someone has to get in one last word. And, others will write commentaries on Stormin Mormon and his religious take on the matter. Sigh.
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Christopher A. Young
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On Sat, 23 Nov 2013 16:09:26 -0500, someone wrote:

Why are all three of mine insulated?
http://farm3.staticflickr.com/2886/10915925156_0e21cf1404_o.gif
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On Mon, 25 Nov 2013 08:21:10 +0000 (UTC), Danny D'Amico

First of all, in North America, the typical p[ower supply is NOT 2 phase. It is center tapped single phase. You have a line1, a line2 and a neutral - the neutral being shared between the two lines. If the load is ballanced between the 2 "sides" there is no current in the neutral. The neutral is regerenced to ground for safety reasons.
In early reural electrification in the USA, single wire distribution was used - using "earth return" It worked, but was fraught with problems, and is virtually unheard of today..
Today's power distribution is 3 phase - with each phase feeding a separate distribution transformer - which has a center tapped secondary for residential power. 3 phase is supplied for industry and some multi-unit residential buildings which run 120/208 instead of 120/240. This is because 3 phase power is 120 degrees phase to phase. because the generating system IS 3 phase, there can not be 2 "phases" 180 degrees apart.
Line1 and Line2 are generally red and black, with the neutral white and safety ground bare or green
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You might as well forget trying to explain that in most of the US the power comes in to the house as a split single phase. Also that unlike a car and much of the electronics where the frame/ground is often part of the circuit, the AC power does not use the ground for anything but safety and not one return leg. There are a couple on here that will never get it.
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On Monday, November 25, 2013 4:26:14 PM UTC-5, Ralph Mowery wrote:

er

I don't see anyone here denying that it's called "split-phase". The transformer splits a single PRIMARY phase. What generally happens when you split something? Do you still have just one? What's at issue is that you have two legs that are 180 degrees out of phase with each other. That simple true statement is where all the diagreement began. You can see two voltage waveforms 180 deg out of phase on a scope. If they were not out of phase by 180 deg, you would not get 240V. Here, from two electrical eqpt manufacturers that talk about two phases, 180 deg out of phase:
http://www.samlexamerica.com/support/documents/WhitePaper-120240VACSingleSp litPhaseandMultiWireBranchCircuits.pdf
http://www.behlman.com/applications/AC%20basics.pdf
And the IEEE clearly agrees that there are in fact two phases present. From a paper presented at a recent IEEE power engineering conference:
"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. Further, the standard 120 /240 secondary is different from the two phase primary system in that the s econdary phases are separated by 180 degrees instead of three phases separa ted by 120 degrees."
Are IEEE power engineers and electrical eqpt manufacturers wrong?
I'm still waiting for someone on the other side of this to give their definition of "phase" and why if one can see two phases on a scope, there are not in fact two phases present.
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On Monday, November 25, 2013 3:10:28 PM UTC-5, snipped-for-privacy@snyder.on.ca wrote:

nning to the house.

The bare wire is the ground wire.

out of phase so the difference between them is 240 volts."

Tell that to my lying scope. You put the two hot legs of the split-phase service on a scope and what do you see? Two phases that differ by 180 degrees. If they didn't differ by 180 degrees, you would not have 240V. It's every bit as real as seeing 3 phases on a scope that are 120 deg seperate.
White papers/app notes from two electrical eqpt manufacturers:
http://www.samlexamerica.com/support/documents/WhitePaper-120240VACSingleSp litPhaseandMultiWireBranchCircuits.pdf
http://www.behlman.com/applications/AC%20basics.pdf
IEEE peer reviewed paper delivered at a recent power engineering conference :
"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. Further, the standard 120 /240 secondary is different from the two phase primary system in that the s econdary phases are separated by 180 degrees instead of three phases separa ted by 120 degrees. "
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On 11/25/2013 05:25 PM, snipped-for-privacy@optonline.net wrote:

How many phases does your oscilloscope show when you put the probe *reference clip* on L1 and the probe *tip* on L2? (Mine shows a single-phase sin wave)
What is the peak to peak voltage when you put the probe *reference clip* on L1 and the probe *tip* on L2?
What is the RMS voltage when you put the probe *reference clip* on L1 and the probe *tip* on L2?
For whatever it's worth, my single-phase central air unit is powered only by L1, L2. The neutral is not used.
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On Monday, November 25, 2013 6:08:36 PM UTC-5, seamus wrote:

ence clip* on L1 and the probe *tip* on L2?

You're never going to see a phase difference looking at just one waveform. There can only be a phase difference between two or more waveforms. Hook the scope to L1, L2, with the neutral as the reference point.

on L1 and the probe *tip* on L2?

the probe *tip* on L2?

by L1, L2. The neutral is not used.
Which doesn't change the fact that you have two 120V legs which are 180 deg out of phase with each other.
Did you see reference to the IEEE paper, delivered at a power engineering conference, that directly addresses the issue? Think the author is just a confused nut? Google "Kersting, W.H." and look at all the dozens of IEEE papers he's written if you have any doubts as to his credentials.
"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. Further, the standard 120 /240 secondary is different from the two phase primary system in that the s econdary phases are separated by 180 degrees instead of three phases separa ted by 120 degrees. "
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seamus formulated on Tuesday :

If you put the reference clip of your scope on either L1 or L2 and you have not somehow floated (removed the ground from your scope) it will likely be the smokey end of the skope and maybe you.
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John G

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On Mon, 25 Nov 2013 14:25:59 -0800, snipped-for-privacy@optonline.net wrote:

These are typical of the breakers in my panel.
My panel was installed by a licensed master electrician. The panel passed inspection.
The breakers are not listed for 2 phase service, only single or 3 phase.
Who should I sue for installing a panel not listed for 2 phase service? The electrician? Electrical inspector? Siemens?
And last but not least, where do I find 2 phase breakers?
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On Monday, November 25, 2013 6:44:17 PM UTC-5, Carson Vos wrote:

I never said I would call the service 2 phase. It's not referred to as that in the industry. There is no disagreement that what comes into the panel originates from one phase of the electrical distribution system. It's like white tissues being called Kleenex. That doesn't change the fact that they are white, soft, tissues, does it?
I'm still waiting for someone on the other side of this to give your definition of the term phase. In electrical engineering, the most basic usage is the relationship between two periodic waveforms, expressed in degrees. If I see two waveforms that are different in phase, be it 120 deg, 90 deg or 180 deg, then there are two phases present and it can be viewed that way.
And what do you say to the fact that you have a very credible, experienced power engineer delivering a paper before the IEEE conf of power engineers that agrees that you have two phases present?
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On Mon, 25 Nov 2013 16:44:45 -0800, snipped-for-privacy@optonline.net wrote:

Well thank God we finally agree it is single phase service.
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On Monday, November 25, 2013 8:36:34 PM UTC-5, Carson Vos wrote:

Again, the disagreement started when the simple statement was made that the two hot legs on a 240v/120v service are 180 deg OUT OF PHASE WITH EACH OTHER. That is absolutely true. The discussion was *not* about what it's called. And technically, it's called a "split-phase service".
I'm still waiting for even one of you alleged experts to give us your definition of "phase" in electrical engineering.
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Um, those are typical ITE style (Siemens subsidiary or bought out IIRC) with a tie handle. The difference is that what you have is a one piece unit, using two single-pole breakers, riveted together at the factory. However, those tie handles may be purchased and it is legal to install them on two separate single pole breakers. I still hate the set-up since in theory when one breaker trips the tie handle trips the other breaker. In theory *cough*. Actually, this version works better than some of the other designs I have seen.
I think you would have a hard time finding a two-phase breaker. Especially one for a 5-wire system. Though, in theory, a single pole breaker could be used for each hot leg of a 3-wire system installed in a single-phase panel. One would have to figure out the math for the magnetic trip portion of the breaker, or only have a current trip. Amperage by any power source is the same, period. Fuses work, too.
(removing tongue from check)
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