Survey on 120/240 volt North American Residential Services

Your points are well founded. The data will be used to determine if a full blown study is called for. Hopefully the people who respond will do so based on their convictions. We will factor in your comments.

I see and concede your point.

When you get close enough to the can to read the label, and you see it says "worms", why do you feel the need to open that can?

A - G - H - 30

North

B-D-H-50

"Guest"

How about 'C' the question isn't right.
If neutral isn't a phase..e.g it's tied to ground/earth it can't be phase shifted relative to anything.

So that's

C, Felis Domesticus G,I, 30

Del anon

Re-read the question. The question is... "is there or is there not a phase shift between the "L1 & Neutral" relative to the "L2 & Neutral".

That is badly worded... If it means a phase shift between L1 and L2 why doesn't it say so?

"L1 & neutral" is a meaningless expression....unless it means the phase difference between 'L1 and neutral'....which as I said before doesn't exist...!

The mentioning of neutral at all is confusing, ambigiguous and irrelevant.

If I really have to spell it out...image I have the two leads from my KrisDel^TM Phaseomatic phase meter each with a croc' clip on the end......

To measure the phase difference between "L1 & Neutral" and "L2 & Neutral" I must connect a croc' clip to each of those two ponts.
How the heck do I connect to "L1 & Neutral" ???? or "L2 & Neutral" ???...
Do you see it is nonsense?

Del

No it is not a "meaningless question". On our system here in North America, we have a potential difference of 120 volts between either of the two lines and the neutral and a potential difference of 240 volts from line to line.

Some people claim, while others do not, that there is a 180 degree phase shift between the two 120 volt systems.

" On our system here in North America, we have a potential difference of 120 volts between either of the two lines and the neutral and a potential difference of 240 volts from line to line."

EXACTLY .... between 2 points L1 & L2

THE MENTION OF NEUTRAL IS IRRELEVANT & CONFUSING

It is like asking what is the difference between.
1&5 and 7&3 ?
It is gobbledegook!

Please read #6 carefully, if you really can't understand the explanations I shall unsubscribe quiety...

Del

I am not asking about L1 to L2. I'm asking about a phase difference between "L1 to the neutral" then from "L2 to the neutral". Perhaps you might want to skip this exercise.

Sorry if I'm being an arse.
I'm not trying to wind you up for the hell of it...there is obviously some missunderstanding of basics somewhere...maybe I'm being thick ... but I think there is no 'phase difference between "L1 to the neutral" ' as you put it.

The phase difference is between L1 and L2... each of which may be measured referenced to any common point.
So to carry out my phase meter (or 'scope) explanation, the meter would have some common connection, like the ground clips on a scope probe...but neutral would not need to be connected at all.

Sorry if I've wound you up or been a pain, cheerio

Del

Del the cat, in the USA the line drop in to the home is 240 ac with a neutral. 3 wires from the pole. The transformer on the pole is a center tap output being fed from one of three phase lines from the power plant.

In the home the circuit breaker panel has the 3 wires in L1 L2 neutral also a ground wire tied to a ground rod. If it is the main panel then the neutral and ground ARE tied (bonded) together. Remote panels have 4 wires back to the main panel and the neutral and ground ARE NOT connected in the remote panel.

I hope this helps.

Now to what the OP is asking; In AC there is only one phase feeding the transformer in so there only one phase out.

Now if you are looking at the AC it self then one half is positive and the other half is negative. But at different times. Even if you used a scope to look at it the peaks would not line up. The positive to negative peaks are 180 degrees out. This is used in AC to DC circuits with Rectifiers.

Sorry for the rambling. And my apology to the OP for discussing this here.

metalSmith's

Hi Del... No you have not wound me up nor are you being an "arse".

I did not want the discussion we are having to take place. I really needed to gauge the "understanding" level of the people who responded. The mere fact we are discussing this at this point, kills the validity of any data I might have been able to collect. That is why I asked for both anonymity and no discussion.

Our 120/240 volt 3 wire residential service used in North America consists of two 120 volt sources. These sources are derived from a common magnetic core driven by a single phase high voltage winding in the utility transformer.

We connect the two windings in series. We call the connection point between the two windings the "neutral" and tie it to ground as our reference.

So... some people call the two power lines "L1" & "L2" while others call them "Phase A" and "Phase B".

The end result is that some people say that the first 120 volt source "L1 TO THE NEUTRAL" is shifted by 180° relative to the the second source, which is "L2 TO THE NEUTRAL".

This, the use of the neutral as our reference point, has contributed to this situation.

Notice I try not to offer an opinion as to which answer is correct, "yes there is a phase shift" or "no there is not a phase shift". I will have to follow JRaef's suggestion and move this effort elsewhere.

If anyone does wish to continue this, please move it to the private message system.

Rick...

Del, in being such a pain, you are pointing out a serious difficulty within the international discussion of electrical practices.

I say ground, you say earth

We use 60Hz, you are 50

I do get the sense that eventually some of the electrical safety differences on how a system gets safely grounded (sorry, earthed to the rest of the world!) will eventually be resolved, but as individuals we do need to open our minds to understand how others understand and describe the issues.

To further cloud the issue, I occasionally get involved with AC grounding, DC negative returns, DC grounding within the same building. Throw in some lightning protection, and there ends up a lot of buried copper for worker safety. It is critical that we all end up on the same page and understand where these electrons end up when things go awry.

I have to agree with Del! There is no "phase difference between either L1-Neut. or L2- Neut. There is only a difference in phase between L1-L2. Neutral is a common (Hence the name NEUTRAL. ie: the definition from Webster-

Main Entry:¹neu·tral Pronunciation: \ˈnü-trəl, ˈnyü- Function:noun Date:15th century

1 : one that is neutral 2 : a neutral color 3 : a position of disengagement (as of gears)

In three phase systems there is a 90 degree shift from L1-L2 and another 90 degree shift from L2- L3. This cancels out the EMF thereby reducing hysteresis and allowing maximum current flow.

Non- eng Electrical tradesman 22yrs. exp

A voltage must always be measured between two points. (There may be considered to be a potential at a point in a field or along a wire, but that potential only has meaning in reference to some other point that is considered zero potential).

Thus the voltage of L1 or L2 is meaningless without defining some point as zero. The only logical zero point for 120V use is neutral, since it is common zero for both phases. In that case, one voltage is the voltage between L1 and neutral (L1-Neut.), and the other voltage is that between L2 and neutral (L2-Neut.), and YES, there IS a phase difference of 180° between those two voltages (L1-Neut. and L2-Neut.)

Likewise a phase shift or phase difference (at least as used in AC power voltages) only has meaning if there are TWO AC voltages. If you measure between L1 and L2, you are measuring a single voltage, so there can be no phase difference.

You must be using a pocket version of Webster! Mine includes adjective definition #7: "in electricity, neither negative nor positive; uncharged" If that doesn't imply zero Volts, then what does it imply?

You say: "In three phase systems there is a 90 degree shift from L1-L2 and another 90 degree shift from L2- L3. This cancels out the EMF thereby reducing hysteresis and allowing maximum current flow." In 22 years, you still haven't learned that the principal advantages of three phase power stem from three equal 120 degree phase shifts, which overlap such that one of the phases is always near peak, so a device can turn on at any instant and have power available at that instant.

I have learned enough to have been licensed as a Journeyman in 4 seperate states.

How many licenses do you hold? have you held?

What is a 'Journeyman' and why do you need a licence??

In the UK we have engineers, technicians and mechanics Where does Journeyman fit in?

John.

after 5 years apprenticeship you test to become a journeyman. Traditionally Journeymen travelled the countryside working under different Masters to develop their trade.

Here in the states we have Electrical Engineers that design the systems, Journeymen who install and repair/ maintain, train apprentices. The license requirement is a way for the local governing body to get more money, with the added benefit that where required the person doing the work is qualified.

E*

*"Electrical" tradesman who has completed training; no longer considered an "apprentice" in the trade union. Note: "E" herein as defined in original post by "North of 60".

Sorry for butting in.

Thanks for the explanation JMM.

It all sounds a bit of a bureaucratic nightmare to me!

We have some daft laws recently passed which means a householder can not fit or modify any electrical wiring in a bathroom with out a certificate of compliance from a qualified inspector... It doesn't matter that you may be a fully trained electrician working in your own house, you would still need to have the inspection done...

Of course most people don't bother, as who is going to enforce it, or even know that you've done the job??

Crazy situation!!

this was me too!

90 degrees?? Seems to me to be 120 degrees in 3 phase...

We had a discussion about this a few months back...

Del, I disagree on this one... If I only connect to L1 and L2, either (A) There is a phase difference between them and I measure a voltage (presumably 240VRMS), or (B) there is no phase difference and I measure close to zero Volts.

But I am a very visually oriented person; I want to SEE the phase difference. To see it, I need to connect the ground of my 'scope (powered through isolation transformer) to neutral, and connect one channel to L1 and the other to L2. When I do, I get the results as Follows:

A-G-H-57

The question has two possible meanings.

If you hook your scope ground to L1 (OK, use an isolation transformer - ruin my fun) and the probe to L2, there is no phase difference.

If you connect the two neutrals (no, I don't know why there are two neutrals - there just are) and then hook the scope ground there, one channel probe to L1 and t'other channel probe to L2, you get a 180° phase shift (just hit the ole A+B) button).

You might consider reposting with a diagram.

But you responded with "B" in your original response to the poll . . . Given your 'scope test, you have just proved it to be "A."

90 degrees out

At my home (and every other one I have checked across the US), all neutrals connect to the same buss bar. There are not two neutrals. Someone mentioned that remote panels had ground and neutral separate. I'm not sure what is meant by that - I've never seen a residence with multiple breaker panels.

dkwarmer and Blink Hello,

What I was talking about in home electrical is; true, most homes only have one circuit panel and the neutral & ground buses ARE tied/bonded together there they are one and the same at that point. There potential should be zero voltage to any thing other than L1 or L2 then it would read 120VAC. of course the potential between L1-L2=240VAC.

The other is sub-panels it could be a retro-fit to an older system,the new system feeding the old or could be an addition needing more space or garage/work shop, or a mobile home, power from the pole to the meter head to a main breaker then 4-wire in to the distribution panel inside.

Like I'd had said to feed the sub-panel the 4-wire cable black/red/white/green go to

black-L1, red-L2, white-neutral, green-ground. The neutral buss and the ground buss should have the tie/bond bar disconnected so the cables carry back to the main panel the neutral and ground separately. The reason is the neutral is to only carry the only the return current from the device. Then the ground only carries the fault current if there is a failure of the device provided it has a ground prong.

By separating the ground and neutral helps to prevent ground loops by having only one common tie point in the main panel.

metalSmith's

Thanks. I had never heard the term ground loop used for powerline AC frequencies, only at much higher ones.

Dick

This is referred to as bonding. Bonding is where the Neutral and ground are electrically bonded to achieve the same difference of potential. Examples:

• the main panel in a home has the neutral and ground bonded.
• If, however, you install a seperate panel in a garage or outbuilding; That neutral would not be bonded to ground.
• This allows for only one return path to ground markedly reducing the chance for an electric shock.

North of 60--

A, E, H, 37+.

Perhaps the wording in the first section should have said "phase difference".

--"anonymous user"

If we call the neutral line 0V, then at 0 degrees, L1 is +120 and L2 is -120. At 90 degrees, all three wires are at 0V. At 180 degrees, L1 is -120 and L2 is 120. That would have to be considered 180 degrees out of phase, wouldn't it? If the (L1 - neutral) signal and the (L2 - neutral) signal were in phase, we wouldn't have 240 V from L1 to L2.

What would the other view be?

In this article, one paragraph reads:

• Power systems in American households and light industry are most often of the split-phase variety, providing so-called 120/240 VAC power. The term "split-phase" merely refers to the split-voltage supply in such a system. In a more general sense, this kind of AC power supply is called single phase because both voltage waveforms are in phase, or in step, with each other.

But just above that statement is this one:

• If we mark the two sources' common connection point (the neutral wire) with the same polarity mark (-), we must express their relative phase shifts as being 180^o apart. Otherwise, we'd be denoting two voltage sources in direct opposition with each other, which would give 0 volts between the two "hot" conductors.

"relative phase shifts". Hmmm. Seems we could say that one is "phase shifted relative to the other by 180 degrees". Or we could say "180 degrees out of phase". If there are two waveforms, there is only one phase shift, (of 180 degrees); there are not two phase shifts that are 180 degrees apart. The waveforms are 180 degrees apart.

I imagine the confusion is exacerbated by the fact that we call the wires of a three phase system "phases", whereas a phase does not really refer to a physical object -- it is a measurement in degrees of rotation.

B, G, H, <1

my answer is B-F/E-H-22

I have been in consumer/Industrial Electronic repair 14+yr

The last 8yrs has been in CEM's systems manufacture and integration and testing.

CEM=Continuous Emission Monitoring

metalSmith's

A-G-H-25

So, here's what I think the problem is. I went to the best visualization I know for checking phases: a lissajous figure. The trouble is that I can't figure out how to connect a scope in the strict meaning of the OP. So, for my two cents, it becomes only a semantic exercise until that is clarified.

North of 60, sorry to so disregard your original instructions, but when you ask engineers...., well

From my way of thinking, The OP mentioned neutral. I think we can all agree that the neutral is connected to ground/earth (and either the center tap of a single winding, or the common point of two equal windings, of the transformer supplying the energy).

The word neutral implies zero Volts. The only way we can have two 120V supplies is for the neutral to be zero. The only way we can get two 120V supplies to add to 240V is if the positive side (at a given instant) of one 120V supply is connected to the negative side (at the same instant) of the other 120V supply.

So for your Lissajous figure, you connect the 'scope's ground to... ground(neutral)! Then you connect vertical to L1 and horizontal to L2, or vice-versa.

I personally prefer to to use the lissajous for observing frequency differences (when reasonable ratios exist), and to observe horizontal displacement of the signals on a chopped dual-trace 'scope for observing phase differences (channel A to L1 and Channel B to L2 or vice-versa).

The only way I could consider the two voltages to be in phase is to make zero be L1, but then we don't have two 120V sources, we have a 120V source between L1 and neutral, and a 240V source between L1 and L2

I agree with every word, comma, and period* in this post. GA I say.

*Although I suppose a period at the end of the post would be a nice touch.

I think using Lissajous figures on an oscillograph to look at phase is an OF thing. When I got my back against a wall and can't think of anything better to do, I often revert to tricks of yesteryear.

I guess the real problem (for me) with this question is what it means to be in phase or 180° out of phase in an electricity system. We call an ordinary transformer single phase, yet the two ends appear to be out of phase relative to a CT. We can't call 240VAC two-phase, so what is it? Does single phase mean out of phase (and, if so, I gotta sneaky question about how a Variac knows how to keep this straight).

I don't know. Do you have a good way to always think about this? I know how to work with the %^@@* stuff - I just don't know how to talk about it.

The only way I could consider the two voltages to be in phase is to make zero be L1, ........

Well, that is not the only way. You could make zero be L2 and follow along with the rest of your argument exactly as before.

Your answer is the best one.

B-D-I-38

A-C-I- 38

Two observations:

1.) For your new survey you might like to distinguish between (or conjoin) electrical engineer and electronic engineer for the UK audience.

I regard myself as an electronic engineer and so answered D not C.

2.) At the top of the page next to the title there is a check box for I want to post anonymously, which nearly everyone ignored.

Having read many of the responses, I must first agree with JRaef, and then with Del.

I think one of the problems you face is that people who have no knowledge of electricity wouldn't know that the wording in question one was good or bad, much less which answer would be right.

Given that, I'm not even going to answer any of them.

By the way, I'm a professional electrical engineer.

"Given that, I'm not even going to answer any of them"

Oh, why not? The correct answer relative to neutral depends thusly:

When Phase "B" mirrors Phase "A"

"A-D-H-30"

When Phase "B" is the reflected image of Phase "A"

"B-D-H-30"

I have solved this riddle. It is the merely the difference between a mirrored composite image and one which passes through a prism.

Explains why it is called "split phase".

I've got a bad case of A-D-H-D-46

And the real answer is: A-C-H-46!

B, D, H, 30 +/-

Anonymous!

Now I will see if I got any of the questions right!

Wow... another thunderstorm.

From start = Question...is it a joke? Somebody needs a Nobel Prize or Ph D in Education? I believe Del sees that way. He (or maybe she - so Pardon Milady!) probably has dozens, hundreds or more of similar pieces, ready to edit e-Pamphlet "Britons about Americans in the Electron World". But if his/her view it is a joke he/she still tried to write something with a sense, to try "a debate in English".

Let me rewrite a story from a Deep South Community College. Y'all could recon it as a penny worth one ( less then 0.01 B. Pound, maybe 1/240 of £).

"At the end of the first semester with the first Lab Experiment in AC Circuits Lab, $99.99 years old Bob the Instructor gave his students a test with question # 13, exactly like the one on the top of this discussion. In the list of multi-choice answers were the same A,B + additionally C answer. C answer was: "None of the above".

Which answer is correct? ....... (fill the blanks)

To prove his point Bob gave his students two sets of oscilloscopes:

1st: dual-channel Fluke with common (COM) for both channels

2nd: two single channel scopes, both with insulated COM.

It took less than 10 minutes to confirm correct answer. Each students started Report's CONCLUSION with words: .................... (fill the blanks).

The End

Gogo La Giraffe"

P.S. Del - I love you man (if woman-oh no- not here!...). You showed me in your question "12v 20AH.." that Euro-Continental people have smaller hour (e.g. 20 Ah in their catalogues) and French Volt is just a v.

P.S.2. I wish I could read here some of the French jokes about Great Britons.

P.S. 3 I gave Very Good/Well note to JRaef. But in my CONCLUSION I would state that the best way to start almost any question I found is in other thread with " Real stupid electrical question.. " which already has over 100 answers. On the other hand my old professor said" There are no stupid questions but there are stupid answers."

>>>>> Strong winds Gentlemen Sailors!>>>>>>

A-G-H-40

A-E-I-20

Trust the American electrical system to be more complicated than it needs to be!

a-d-h-38

Am I the only one here to find this thread rather disturbing?

Most of the engineers on here are from the USA but yet they don't understand what form the electricity supply is in their houses??!!!!!

I am amazed / astounded / astonished / but also very disappointed.

Hi, North of 60.

Just wanted to apologize for my contribution to derailing the intent of your thread. I agreed with JRaef's first post, and in addition had the feeling that identifying oneself (as, for example an EE w/30 years experience... or as "other" with 1 year) would further color the responses beyond the tendency to post in concert with the majority view. I took your post number 8 as a sign that you felt the thread was already derailed, or that there might be a better survey technique.

I think it is a good thread (although the question seems a bit ambiguous), and warrants further discussion, because it appears there is some disagreement regarding the phase relationship of the two 120 volt supplies. It would be interesting to know, I think, if that means that people do not agree on 1. the actual wiring or 2. the meaning of the word "phase" (chemical engineers know what "three phases" mean: solid, liquid, and gas ) 3. the location of the zero reference, or 4. other stuff.

BTW, another problem with conducting the survey here is that you may find that your sample size is much too small to make any conclusion, especially given the number of variables measured. For example, you might not be able to say anything at all about the perceptions of "highly experienced electrical engineers residing in North America" because the sample size of people meeting those three qualifications is much too small. (Also, be aware that most CR4 members are teetering on the brink of insanity, so your survey results would have to have a disclaimer to that effect.)

In your future surveys, perhaps you could have one survey for only experienced EEs and another for only experienced E techs (or something along those lines) and not have respondents identifiable to others in any other way.

Thanks Ken...

B--- E---22

this was me. I was logged in on another comp. sorry.

A-E-H-28

All answers show something strange. According to simple Truth that in Engineering/Physics the only one answer could be True we got A and B as a correct answer from the persons with this education and experience. Strange?

No the answer TVP / # 30 / cited below gives proper opinion about The Question and available only two possible answers A and B:

Well, of course. Remember that I'm both an engineer and a liberal. So, if you ask a question, I give at least four answers:

1) choice "A"

2) choice "B"

3) there's not enough information

4) I don't want to hurt the self-esteem of those who are wrong

Anyway, in the middle of my scope experiment and answer, I realized that I would have answered differently if I had done that first.

I see I must to send this to my Bob the Instructor (if he still teaches). Maybe he will change his multiple choice answers from 3 to 4. By the way his students' CONCLUSION started with "It depends..." - see Gogo La Giraffe's story.

Above Answer 4 rather does not apply to the students, right?

Where we are after almost 60 answers?

After reading all of them I probably see answer 20 to be the most valuable, let me cite part of it:

Well, of course. Remember that I'm both an engineer and a liberal. So, if you ask a question, I give at least four answers:

1) choice "A"

2) choice "B"

3) there's not enough information

4) I don't want to hurt the self-esteem of those who are wrong

Anyway, in the middle of my scope experiment and answer, I realized that I would

have answered differently if I had done that first.

So I should write to my Bob the Instructor (if he still teaches in the South) to maybe correct his test question # 13. His story had his students' CONCLUSION first words: "It depents..."

In this discussion CONCLUSION should start with same words.

This tread should apply to North American electricians/master el./engineers with associate - bachelor - master degrees or maybe only Ph D owners?

Del the CAT brought "refreshing" UK /EU point of view. Somebody mentioned a history of USA / Canada NEC editing. Its changes' history which suppose to follow changes in the el_technology. My questions would be:

Is it true that EU in the end of XIX and beginning of XX century had 110 V ac as a standard? And with increase of loads (Watts & Amps) demand they switched to 220 Vac?

In their, not exactly parallel decision (Internet should be invented then!), N. Americans left standard 110 (frankly moved to 120Vac) with their small appliances when higher power consuming (ranges, dryers, HVAC etc.) created 240V standard that in the new needs of two voltages led to 120/240V, 60 Hz single phase secondary winding in residential house services. And this system has not guaranteed a power per phase balance as well in L1-N/L2-N/L1-L2 sections.

EU/UK residents living mostly in apartment buildings could have only one standard 220 Vac appliances supplied by single phase feeders from 231V secondary transformer windings, with mostly underground (under-earth?) cables grid. Or even having 220/380 Vac 3-phase motors (smaller in size per kW than single phase 230 Vac ones Made in Canada) supplied from 3-phase 400/231 V, 50 Hz.

In the different world on this side of Atlantic home owner + electric company delivering energy via overhead lines saved on installation of small cylindrical single-phase transformers on the wooden poles.

It is good. The experts from both side of Atlantic have still jobs just to adapting designing projects down "by others" and manufacturers keep the monopoles on their regional markets.

Why nobody's drawn the diagram of 120/240 V, 60 Hz service with terminals to connect the scope(s)? It would be less confusion and even insults. North of 60?

In transformers N. Ams have Open Delta and other connections used for three single-phase loads, EUs 3-phase Zig-zag to fight with time-changed 3-phase unbalance.

More cables in EU, more O/H lines in America - in the grids below 50 kV (arbitrary value)

UN cannot make forcible resolutions for EU, UK, US etc.in this matter.

Anybody could add or correct this hi-story? Andy G.? Del the.? .....

Any links?

This was a rather simple request... answer the questions and stay anonymous and offer no explanation.

The questions were built using methodology that addressed MY need.

Question one is binary... either there is a difference in the phase angle (or whatever language you think is appropriate to use to ask the question) between the two 120 volt sources, relative to each other, or, there is not. Period!

About the only change I think I should have made to question #1 is to add a third option for "I don't understand the question and as such, I don't know how to answer it".

This effort is blown and the only usable data it has returned is to validate JRaef's comment at the beginning.

I'm rather disappointed and will look for another venue for this research.

Hello North of 60, This is no insult intended here just jest!

You don't play fair, I'm taking my Questions and going somewhere else to play!

Good luck with your test, when you get it set up again and you would like our
input to skew it for you just post a link here.

metalSmith's

Hey, it's not unusable data! Just change the research topic to "can electrical and other engineers follow simple printed instructions to solve simple uncomplicated problems". I think you have enough responses to derive an answer...

Thanks for the chuckle...

Or (it is almost like asking:)

Q: Is Red:

A. White

B. Black

so is it Binary? Yes or No? True or False? On or Off? Smart or Stupid?

We believe this method of explanation (almost stupid) is called AD ABSURDUM.

Trying to fool engineers?

B - E - H - 12

A, F, H, 17

BCH 38