I am in the final stages of writing a book titled The Horse Barn. A portion of the book (8,000 words) relates to electrical design and installation.

I am looking for a qualified electrician to check the electrical portion of my manuscript for accuracy, especially concerning safety and legal issues. There would be no monetary compensation, but I will acknowledge the reader in the book.

If anyone is interested or can recommend someone, please contact me at rklimesh@horsekeeping.com. Thank you.

Would you mind posting a couple of paragraphs to give an idea of how this reads at present?

Sure. Here's an exerpt.
Electricity from the local utility company is typically supplied through three overhead or underground wires called service conductors. An electric service or feed consists of two "hot" leads (wires) each carrying 120 volts, and one "neutral" lead. Two hot leads are used together to provide 240 volts when needed. The wires pass through a meter and into the service panel of the building where they connect to metal strips called buss bars (9.1). The neutral wire and another "safety ground" or "green" wire (often bare copper) connect from the service panel to a copper rod driven into the earth. Three wires, hot, neutral, and safety ground make up the connections found in a typical outlet receptacle.
You may wonder why both the safety ground wire and neutral are needed since both ultimately connect to the same ground rod. Actually, the safety ground wire isn't needed as evidenced by the large number of electrical appliances which only use only two (hot and neutral) prongs. But, in electrical equipment which has a safety ground connection (a three pronged plug), the round grounding prong is always connected to any exposed metal parts of the equipment. That way, if an exposed part of the equipment becomes energized due to a wiring fault inside the equipment the safety ground connection causes the hot connection to be directly connected to earth, and the fuse or circuit breaker would shut down power to the circuit. Equipment with two-prong plugs usually has a non-conducting plastic case so errant electricity cannot pass to a person or horse touching the case.

I like that!

That's the perfect name/description for the equipment grounding conductor, much more intuitive! Bravo... You sure you need our help? You're off to a great start there!

Thanks for the kind words. It's good to know I'm on the right track. Since I'm not an electrician, I want to run the info by a professional to make sure I don't mislead readers.

I can see that you wouldn't want me editing it!


Electricity from the local utility company is typically supplied through three or four overhead or underground wires called service conductors.
Sure they run a lot of overhead triplex on a farm. But if you don't want your animals experiencing stray voltage, four are better.

An electric service or feed consists of two "hot" leads (prounounced >leedz< ) (wires) each providing 120 volts, and one "neutral" lead. Two hot leads - which are out of phase to each other - are used together to provide 240 volts where needed. The wires pass through a meter box and into the service panel of the building where they connect to metal strips called buss bars (9.1).

(In some cases, the farm exception, the meter is on a pole and the service splits to the house and barn from there.)

A "safety ground" or "green" wire (often bare copper) connects from the service panel to copper rods (electrodes) driven 8' into the earth.
The neutral wire from the utility is also tied to the safety ground.

Three wires: one hot, a neutral, and a safety ground make up the connections to in a typical outlet receptacle.

You may wonder why both the safety ground wire and neutral are needed since both ultimately connect to the utility's neutral.

The safety ground wire isn't always needed as evidenced by the large number of electrical appliances which only use only two (hot and neutral) prongs. But, in electrical equipment which has a safety ground connection (a three pronged plug), the round grounding prong is always connected to any exposed metal parts of the equipment. That way, if an exposed part of the equipment becomes energized by wiring fault (failure) inside the equipment the safety ground connection causes the hot connection to short circuit without having to follow an unanticipated and potentially lethal path, and the fuse or circuit breaker should shut down power to the circuit.

Equipment with two-prong plugs usually has a non-conducting plastic case so errant electricity should not pass to a person or horse touching the case.

Sorry, I won't do the rest free.

"An electric service or feed consists of two "hot" leads (prounounced >leedz< ) (wires) each providing 120 volts, and one "neutral" lead. Two hot leads - which are out of phase to each other - are used together to provide 240 volts where needed."

Huh? Out of phase? But isn't this single phase? I like this description much better.

A single phase, AC service drop consists of two ungrounded (hot) conductors, with a potential difference of 240 volts nominal between them, and a grounded (neutral) conductor with a potential difference of 120 volts nominal between it and either one of the two ungrounded conductors.

I also have a little trouble with the word "carry" with regard to voltage. I think a more accurate term would be "supply". The conductors are not really carrying voltage, they are carrying an amount of electricity that is measured in amperes that are being supplied or propelled by voltage (electrical pressure).

If we use the old water analogy here with regard to a water hose, the voltage would be compared to the water pressure, and the amperes would be compared to the volume of water in the hose. Using this logic, we could make the statement that "X" PSI of water pressure is supplying the water hose with "Y" gallons of water. The hose does not carry pressure, but rather it carries water, that is being supplied by pressure.

Also, when referring to a nominal voltage such as 120, you cannot really say that an individual conductor supplies 120 volts, it must have another conductor of which to compare this potential difference. For example, "Either one of the ungrounded (hot) conductors has a potential difference of 120 volts between itself, and the neutral conductor". It may have a potential difference of 120 volts to earth ground, but it is also true that it could have a potential difference of 50,000 volts to a passing thundercloud.

Matt



[This message has been edited by Matt M (edited 05-11-2001).]

Here you go guys...
https://www.electrical-contractor.net/ubb/Forum1/HTML/000101.html

The two hot conductors are typically 180 degrees out of phase. This is why you get 240 between the two hots and 120 from each hot to ground. If you got 120v from each hot to ground and 120 from hot to hot it wouldn't make much sense to have a three wire system. There are still a lot of two wire systems which are referred to as single phase--single phase, two wire. On this system, one wire is hot and one is grounded.

As far as the descriptions for the book, as long as you make mention that this is not an electrical training maual and that anyone who is not qualified should seek the skills of a professional electrician, your description is fine.

If they were 180 degrees out of phase, you would have nothing.

Sorry to burst your bubble..

Where's Scott? Hmmm, how would he handle this...



The reality is that the secondary coil in the transformer is center tapped to neutral (grounded conductor) in a 240V single phase system... the center tap splits up the two 120V legs.

Notice that the transformer outside your home is tapped to only one ungrounded high voltage conductor, hence single phase.

First, technically, there is no neutral in a single phase system. The white (or natural grey) wire is called the "grounded conductor". This is not to be confused with the "ground" (green or bare wire) which is called the "equipment grounding conductor".

In a 120/240 Volt Single Phase system, the transformer secondary coil is "center tapped" to ground which defines the grounding conductor's voltage as "zero". The right and left extremes of the secondary coil are the taps for each 120 Volt leg. Voltage from either the right or left tap to the grounded center tap will be 120 Volts or thereabouts. But the voltage between the left and right taps are 240 Volts, not involving the grounded conductor at all.


[This message has been edited by sparky66wv (edited 05-11-2001).]

I should mention that electricians are some of the most nitpicky people on the planet... Comes with the territory!

klim,
I hope we haven't completely scared you off, Scott35 is the moderator of our Electrical Theory section , wait for his reply to this, he has a way of explaining things.

As far as editing, I would, but I'd want Scott, Bill, Steve, Don and Frank to proofread mine! Whew!


[This message has been edited by sparky66wv (edited 05-11-2001).]

Exactly Sparky66!

With respect to the number of phases that a particular system has, for all practical purposes we are really refering to the number of sine waves present. With single phase, we have one sine wave. If we could slow time down and look at the current flow on a single phase circuit, at a point where current is flowing "IN" one of the conductors, you can bet the farm that it is flowing "OUT" the other.

Because we only have two conductors that we can measure a potential difference between, we can only have one single voltage. The amplitude of the voltage is the same throughout the circuit at any point in time.

Conversely, on a 3 phase system we have three seperate sine waves. If we superimpose these sine waves over each other, we would see that each phase is typically 120 degrees out from the next.

Matt

Hi everyone.

In my opinion I think the text is great! There's really no need to throw a bunch of tech info at persons unfamiliar to the whole thing - it scares normal people
We, as electricians, and especially me for example, tend to want endless and complete details conserning our field's technical issues. This is the way we should be!!

The document was, to me, well written and easilly understandable by the general public.
It's just substandard to us sparkys because it lacks tons of detail! [and we've seen that type of system a million times before].

Maybe one thing could be changed - in order to keep confusion down: instead of saying the 240 VAC conductors are 180 degrees out of phase, just say that there's 240 volts between them. Keep it simple on that part so the people can understand and don't get stuck in never-never land thinking about math and theory.
[it also keeps the flames from sparkys like myself, to a minimum ].

Now I'm not too sure if that stuff was in the original text, or just something generated here - sorry!!

Scale of 1-10, I give it 10!

Virgil,

You've nailed that 1 phase system!! Great job!!!

Nothing I could add to this thread that would be any different than what's already here, so I'll continue bouncing around the forum.

P.S. I will be posting a few schematics to the theory area tonight - a couple are on those 6 and 9 phase rectifier transformers shown in the pictures.

Scott SET

Hey Scott, you tryin' to scare away the laymen?



FYI:

6 and 9 phase rectifier transformers are used to convert AC power to DC power more smoothly than three phase rectifier transformers. Case in point: My old TI30 calculator won't run on a 9V wallwart (single phase rectifier transformer in miniature...) due to the poor DC power quality, which demonstrates why these exotic creatures are useful in todays electronic world.

klim;
just a suggestion here, might you consider letting the forum access this 8000 word file?

perhaps an adobe acrobat deal?


like Virgil said, we are kinda knit picky, and you'll get 10x the feedback utilizing a bunch of us

besides, i wanna get to the equopotential plane part.....

Klim,

Personally I like your wording so far including the way you describe getting 240 volts. It should be easily understood by most everyone. I do have a suggestion about changing something though.


I think the word 'earth' should be changed possibly to 'service ground'. It's true that the Hot connection will be connected to earth, but that in itself really won't do anything. What causes the fuse or circuit breaker to shut down is the fact that it is now connected to the neutral coming from the service.

Perhaps someone can explain it better than I, but I feel that it is an important point to be made and it would be best if it was as correct as possible and not perpetuating a popular misnomer.

Are any in agreement?

Bill

Bill;
a strong second here.

but now we would owe klim's book an explanation of why agricultural building need to be overgrounded.

(de plane, de plane Boss.....)

No, sir. I discussed this with Scott35 before. I say that if he can have 9 phases, then I can have two.
Although drawn from one phase, the center tap on the secondary winding splits it into two phases. I called them poles to avoid having to argue with Scott.

But you said nothing of why there are 240 between them. It's not like one is +120 V and the other -120 V.

You just glossed over one technicality and dug into two more.

Yeah, supply/provide/whatever. Carry is for current.

Did you forget to mention that this is a sinusoidal waveform and 120 V is the RMS? No, really, I wasn't trying to overcomplicate it.

I was trying to leave out the details that don't seem important to casual users without saying something wrong.

... like focusing on the importance of the neutral to complete the circuit rather than a ground rod.

My Mom knows first hand of what can happen in a dairy milk parlor. I got 43V RMS from the milking stall to the wet drain after she complained of getting shocked.

So where does this stray (or floating) voltage come from?
The soil/concrete/water/steel acting as a battery?

Bonding the milking stall to the ground bus cured that one... down to 1.5V RMS now...
about 50 years too late for an equipotential plane though... (Jack hammer time?...not me!)

You didn't burst my bubble because I am correct. Scott appears to agree (or he's scared to upset me).

Heh, heh. Well, those two legs are 180 degrees out of phase.

Notice that Scott's 9 phase transformer is tapped on just three phases, hence three phase. Ooops!

Give us a break! We know what we mean. We know the technical terms. This is a horse book were talking about!! Oh, and by the way, there is no such thing as natural grey thermoplastic insulation.

We know. That was explained. Did you read the chapter? Has you user ID been taken over by a newbie?

I agree, although it wouldn't hurt to educat them a little bit by exposing them to a few salient details.

I didn't say that the 240 VAC conductors are 180 degrees out of phase, I just just said out of phase so that the reader would know that they were both 120 V but there was some good reason why together they make 240 V.

Right.

I had a problem with "You may wonder why both the safety ground wire and neutral are needed since both ultimately connect to the same ground rod."

I changed ground rod to utility neutral since that is the key connection to complete the circuit.

Burn Baby Burn!!!

Man, this is supposed to be fun Dude...

Look, your blood pressure is rising.

So you're telling me that when you hook 240V up to an oscilloscope that you will see two independent sine waves 180 degrees apart, or will it look just like a 120V sine wave with twice the amplitude?

Precisely...that would be 180 degrees out of phase and produce 0 volts.

Got to admit you have something there with the 6 and 9 phase thing, although lag was mentioned to be more of a factor there.

Waves 180 degrees apart will cancel each other out assuming everything else is equal. Please do not attempt to change the laws of physics to support your arguments.

Thank you.

BTW, if you had been as observant as you think you are being, you would have noticed that my post explaining 120/240V systems was cut and pasted from another post. Pardon me for not editing out anything redundant.

Once again, thank you.

Oh yes, and I've learned that it is better to let people think you're dumber than you really are rather than the other way around.

Just a thought...

Oh yes, and if I had failed to mention the "natural grey" part, you seem like the type that would have jumped all over that too.

[This message has been edited by sparky66wv (edited 05-12-2001).]

Steve T was the one who said . I was speaking to him as well.

Anything but single phase will require a variable equal to the square root of the number of phases multiplied by the line to ground voltage to achieve the line to line voltages.

Square root of three = 1.73... 120 x 1.73... = 208

Square root of two = 1.41... 120 x 1.41... = 169.7... not 240. So to acheive 120V to neutral on a 2 phase system would require 169.7 Volts line to line.

Please explain how your description fits into this picture. It wouldn't be the first time that I was missing something, and I'll freely admit to being wrong if you are able to convince me as such.

May I suggest that We are now unneccesarily overcomplicating this discussion that Klim had initiated.

Can any disputes over technical details please be taken to the 'Theory' area? And, please try to keep the flames low, The smoke detectors will start going off soon!!


Bill

[This message has been edited by Bill Addiss (edited 05-12-2001).]

Sorry... Yes I am the King of Digress!

Thanks, everyone, for your replies. I do mention in the electrical section of the book, as Steve T. suggested, that this is not an electrical training maual and anyone who is not qualified should seek the skills of a professional electrician.

Sparky, I can't imagine posting 9,000 pages and trying to sort through all the answers and ensuing discussions! I just need one electrician to check the manuscript.

I'd like to keep the book reader-friendly and give readers a basic idea of how electricity works in their barn, and not scare people off with too many technical details.