Need neutral explanation for dummies

[catfish500 mark]

Can someone, anyone plz plz plz explain the difference between a neutral and a ground and what purpose the neutral serves and how it works without getting so technical that novices like myself cant understand.Some will say its just another ground and some will say it isnt, but if it isnt how can it be tied to the ground in certain situations.Dangit Im so confused, grrrrrrr

 

[Charles (in GA)]

A neutral is a "grounded conductor"

If you look at the transformer on the pole supplying your house, you see it has three wires coming off the side of it, going to your house. Two of the taps, the hots, come off the ends of the transformer secondary windings. If you measure the voltage across these, you get 240v. The center tap is the "neutral" which is known as the "grounded conductor". This tap comes off the middle of the secondary winding of the transformer. It stands to reason, if the entire length of the winding gives you 240v, then half of the winding will give you 120v, which it does. A 120v circuit is created by using one of the hots, and this neutral, the center tap off the winding of the transformer. This neutral is also connected to a ground wire, that runs down the pole and all the way to the bottom of the pole. As it arrives in your house, the neutral is connected to the same terminal that the ground is, which is connected to the ground rods, and possibly water pipes.

The ground circuit is for providing a path for short circuit current to travel back to ground. Current normally does not travel on this ground circuit, even though it is connected to the neutral at the service entrance.

 

[wyliesdiesels]

Hopefully the OP isnt in England or a country other than the US otherwise hes gonna be more confused...

 

[damienga15de]

I always explain electricity like this,

Picture it as a water supply being pumped constantly the live / hot being the flow and the neutral being the return, outlets can be thought of as taps to allow some of the water out of the system,

This works fine until the return / neutral breaks the ground is there as a backup to the neutral

Sent from my GT-I9505 using Tapatalk

 

[catfish500 mark]

Im wanting to know how electricty works and at least have a good general idea of what happens when something goes bad.Anyone such as myself can hook up wires but UNDERSTANDING the concept of current is another.I suppose I have found a new quest in my life and that is to learn about electricty and how it works.When I get this compressor install completed Im gonna make it a mission to learn and understand about this subject.I never knew I liked electricty until the past couple of months and now I cant leave it alone.Thanks for the replies fellas they did help me a bit.

 

[DekeT]

Im wanting to know how electricty works and at least have a good general idea of what happens when something goes bad.Anyone such as myself can hook up wires but UNDERSTANDING the concept of current is another.I suppose I have found a new quest in my life and that is to learn about electricty and how it works.When I get this compressor install completed Im gonna make it a mission to learn and understand about this subject.I never knew I liked electricty until the past couple of months and now I cant leave it alone.Thanks for the replies fellas they did help me a bit.

Physics textbooks are the best source of understanding the concepts of electricity.

 

[David Paul]

Great explanations. I knew how to make the correct connections, now I know why I was doing it.

 

[torqueman2002]

Physics textbooks are the best source of understanding the concepts of electricity.

+1

I have my HS Physics text book and refer to it from time to time.

I also use this book a lot! It was a gift back in the 70's when I bought a craftsman style double house that needed a lot of TLC.

http://www.amazon.com/Readers-Digest-Complete-Yourself-Manual/dp/0895770105/ref=sr_1_4?s=books&ie=UTF8&qid=1416322613&sr=1-4&keywords=readers+digest+home+repair+book
[This is a link to a used book, Amazon also has new updated publications.]

Another great source is this book, I used it when wiring my garage/shop with a sub-panel for 220V for the compressor.

Wiring a House, 4th Edition (For Pros By Pros) Paperback
[Again, there is a newer 5th edition listed by Amazon.]

 

[JohnX14]

I think part of the confusion with the term "neutral" is that many people, even electricians, refer to the ungrounded (white) conductor of a simple 120v circuit as a neutral. As most know, it's not a neutral, it is an ungrounded current carrying conductor. But it's become a slang which can confuses a lot of folks.

 

[Nick Danger]

A neutral is a "grounded conductor"

If you look at the transformer on the pole supplying your house, you see it has three wires coming off the side of it, going to your house. Two of the taps, the hots, come off the ends of the transformer secondary windings. If you measure the voltage across these, you get 240v. The center tap is the "neutral" which is known as the "grounded conductor". This tap comes off the middle of the secondary winding of the transformer. It stands to reason, if the entire length of the winding gives you 240v, then half of the winding will give you 120v, which it does. A 120v circuit is created by using one of the hots, and this neutral, the center tap off the winding of the transformer. This neutral is also connected to a ground wire, that runs down the pole and all the way to the bottom of the pole. As it arrives in your house, the neutral is connected to the same terminal that the ground is, which is connected to the ground rods, and possibly water pipes.

The ground circuit is for providing a path for short circuit current to travel back to ground. Current normally does not travel on this ground circuit, even though it is connected to the neutral at the service entrance.

I'm confused. It sounds like the two hot lines are 180° out of phase. How are they wired to the panel -- one line to the left bank and one line to the right bank? If a 240V breaker is only on one side, how does it deliver the voltage?

 

[catfish500 mark]

At least now I dont feel so bad about not understanding the term neutral, and its function and purpose.I always felt that it was a wire that if a short cccured it would let the electricity go back to the ground rod instead of to the person in contact with the cord or tool.But when I started to learn about subpanels and discovered that the neutral and ground had to be seperated I felt I no longer had a understanding of a neutral, because if the neutral is not connected to the ground what purpose does it serve at this point, or where does the shorted out electricty go since the neutral is no longer grounded.Perhaps Im just making it more difficult than it actually is.I should clarify that Im thinking of a 240 circuit.

 

[danb35]

I'm confused. It sounds like the two hot lines are 180° out of phase.

Correct.

How are they wired to the panel -- one line to the left bank and one line to the right bank?

Nope, the bus bars are designed in such a way that adjacent slots are connected to opposite "legs" (or hot lines). If we take "1" to refer to one leg, and "2" to refer to the other, the slots in a typical panel would be connected like this:

1 2
2 1
1 2
2 1
1 2
2 1

In this way, a 240V breaker connects to both legs.

 

[theoldwizard1]

... neutral is designed to be a "return path" for electricity flow during normal everyday use.

... ground should do nothing under normal use. It is only there to protect you from electrocution if something undesired happens within the circuit

The above is really all the average person needs to know !

 

[Nick Danger]

Correct.

Nope, the bus bars are designed in such a way that adjacent slots are connected to opposite "legs" (or hot lines). If we take "1" to refer to one leg, and "2" to refer to the other, the slots in a typical panel would be connected like this:

1 2
2 1
1 2
2 1
1 2
2 1

In this way, a 240V breaker connects to both legs.

Slaps forehead. Of course. Thanks.

 

[danb35]

At least now I dont feel so bad about not understanding the term neutral, and its function and purpose.I always felt that it was a wire that if a short cccured it would let the electricity go back to the ground rod instead of to the person in contact with the cord or tool.

No, that's the function of the ground (green or bare, what the code calls the "grounding") wire.

 

[catfish500 mark]

The above is really all the average person needs to know !

So is it like a return fuel line on a vehicle, being that the fuel pump is constantly pumping fuel but the engine is using only so much of the fuel so its necessary to have a way of getting the unused fuel back to the fuel tank to be used again when needed?

 

[Nick Danger]

So is it like a return fuel line on a vehicle, being that the fuel pump is constantly pumping fuel but the engine is using only so much of the fuel so its necessary to have a way of getting the unused fuel back to the fuel tank to be used again when needed?

It's more like a water wheel. The water has to flow past the wheel for the wheel for it to work. The electric utility provides the pump that pushes the water back to to the top of the hill.

 

[jkwilson]

Standard US service consists of 3 hots or 3 phases that are separated by 120 degrees from each other in time. Any two can provide 220 service, and any one phase can proved 120 service along with the neutral.

On a 120V 60Hz circuit, the current changes direction 60 times a second. The current in the neutral is the same as the current in the hot. The neutral is connected to the ground at the panel so that the ground wire can serve as an alternate path if a fault occurs in the equipment. Since the ground isn't connected to the neutral at the equipment end, current only flows in the ground if there is a problem.

For 220 only circuits, the second hot is the other part of the path and the neutral isn't used. There are combined 220/120 circuits that use all four wires.

 

[pattenp]

I think part of the confusion with the term "neutral" is that many people, even electricians, refer to the ungrounded (white) conductor of a simple 120v circuit as a neutral. As most know, it's not a neutral, it is an ungrounded current carrying conductor. But it's become a slang which can confuses a lot of folks.

The neutral is a grounded conductor. Ungrounded current carrying conductors are the hots.

 

[catfish500 mark]

I sure wish I had known 30 yrs ago that I was so intriqued about electricty.I guess I may have missed my calling, but the subject of electricty will be one that I will be constantly trying to learn more about from now on.This site is just so informative but its the people on here that make it that way.Thanks again fellas and I hope Im not being too much of a pita (lol).

 

[teamextreme]

This works fine until the return / neutral breaks the ground is there as a backup to the neutral

No, the ground and neutral serve two completely different purposes. The ground is NOT a backup to the neutral, or vise versa.

Ground conductor (green/bare) is for safety to prevent shocks. No current flows through this wire under normal conditions.
Neutral or grounded conductor (white) is the return path for electricity. Current flows through this wire.

 

[sberry]

At least now I dont feel so bad about not understanding the term neutral, and its function and purpose.I always felt that it was a wire that if a short cccured it would let the electricity go back to the ground rod instead of to the person in contact with the cord or tool.But when I started to learn about subpanels and discovered that the neutral and ground had to be seperated I felt I no longer had a understanding of a neutral, because if the neutral is not connected to the ground what purpose does it serve at this point, or where does the shorted out electricty go since the neutral is no longer grounded.Perhaps Im just making it more difficult than it actually is.I should clarify that Im thinking of a 240 circuit.

A fault

I always felt that it was a wire that if a short cccured it would let the electricity go back to the ground rod instead of to the person in contact with the cord or tool

The protection kind of occurs by default. Yes you want a path with low resistance back to the source in this case being the ****** not the earth thru a rod.
But the whole scheme is designed to protect by keeping you at very little potential difference from the ground you are standing on and the equipment. W

 

[sberry]

I don't know of much equipment in diy that takes more than 2 wires to run besides dryer and some ranges?

 

[sberry]

I don't know anything about electricity. It is over my head. Being a wireman and installer is different skill,,, ha

 

[sberry]

This is some of what we were discussing about one of the welding carts in the fab section where a ground wire was being used as a current carrying conductor to run grinders. If there was an interruption of the ground wire at the plug would energize the cart with 120 when the trigger was puled on the grinder.
With insulated grounded conductor the machine simply stops should the plug come half way out or get a loose connection.
I am glad to see the old bonded 3 wire appliances gone.

 

[6768rogues]

I'm confused. It sounds like the two hot lines are 180° out of phase. How are they wired to the panel -- one line to the left bank and one line to the right bank? If a 240V breaker is only on one side, how does it deliver the voltage?

I changed my post because what I posted was not correct. I went back to my text book and reviewed it. It has been a long time since I studied electricity in college and my senior brain had a cramp. Thank you for correcting me.
Subsequent posts address what I said in error and I am glad that I was set straight.

 

[mikehaugen]

In single phase 240 volt residential electricity, the two hot lines are not 180 degrees out of phase. If they were, they would cancel each other out and there would be no power.
They are in the same phase so they are additive, two 120 lines gives 240 volts.

This is not correct. 180 degrees apart means they peak at the same time, just one is positive and one negative 120. They are also both zero at the same time.

 

[mikehaugen]

In single phase 240 volt residential electricity, the two hot lines are not 180 degrees out of phase. If they were, they would cancel each other out and there would be no power.
They are in the same phase so they are additive, two 120 lines gives 240 volts.
In three phase electricity, the three phases are 120 degrees apart. Their resultant power is not additive, it follows a root mean square function. For example, three 277 volt supplies in three phase result in 480 volts.

This is not correct. 180 degrees apart means they peak at the same time, just one is positive and one negative 120. They are also both zero at the same time.

Okay, now I am doubting myself. What you said makes sense. However everything I have ever read describes them as being 180 apart, resulting in 240 difference. Drawings I've seen depict 2 sine waves 180 degrees apart, so now I don't know.

 

[mikehaugen]

Yes, single phase residential wiring that is 120/240 contains two hot lines 180 degrees out of phase with each other. Neither phase ever climbs to more than 120v RMS to ground, but when combined together they create 240v between each other because of the phase offset difference. If it is confusing, think of it more as it actually works. AC is a constant push/pull rather than a constant flow like you see with DC in your car. With normal 120v the electricity pushes with 120v of force (pressure) and then pulls with 120v of force 60 times per second. When you add a second hot wire that is 180 out of phase, they do not cancel but add together. When electricity is pushing in with 120v of force on phase A it is at the same time pulling out with 120v of force on phase B which creates a 240 volt RMS difference that the motor etc.

It might also help to think of the two legs as being opposite polarity at any given time vs thinking of it as them being out of phase with each other.

Also another thing is that when the AC sine curve is in the negative on a regular 120v circuit that uses a hot and neutral, for 50% of the time (when the sine curve is in the negative range) the current is actually flowing from the neutral to the hot! That's how the push-pull back and forth at 60Hz frequency is created.

Okay, this is exactly the way I understood it, but what rogues posted threw me a curveball.

 

[dragonballz]

This is even more confusing if you're an auto-mechanic

 

[RPH]

"Neither phase ever climbs to more than 120v RMS to ground, "
Interesting statement. I work with induction equipment and we take 480 vac rectify it to dc. Average dc bus voltage is 650-690 vdc depending on line.
Care to explain? No transformers involved.
Two numbers that are important in ac equations are 0.707 and 1.414. It involves the rms thing. Peak voltage on 120 vac is about 187 vac, peak to peak is even higher.

 

[wyliesdiesels]

At least now I dont feel so bad about not understanding the term neutral, and its function and purpose.I always felt that it was a wire that if a short cccured it would let the electricity go back to the ground rod instead of to the person in contact with the cord or tool.But when I started to learn about subpanels and discovered that the neutral and ground had to be seperated I felt I no longer had a understanding of a neutral, because if the neutral is not connected to the ground what purpose does it serve at this point, or where does the shorted out electricty go since the neutral is no longer grounded.Perhaps Im just making it more difficult than it actually is.I should clarify that Im thinking of a 240 circuit.

Ground rods have NOTHING to do with ground faults. People commonly confuse EGCs/grounds and grounding electrodes such as rods. Grounding rods are for grounding lightning! EGCs are for protection from ground faults such as when a winding in a motor shorts to the metal housing which when grounded causes the breaker to trip!

 

[chrispyny]

Freddi,

Thanks for your explanation of split phase/3 phase and why i see 240v single phase as opposing waveforms. I ACTUALLY grasp it all now. The part about what reference is used clearly explains 2 opposing waves, and how its all still single phase in the end.

I work on the low voltage side of the house as a telco field technician so -48v dc is vastly different from this stuff but im doing some continuing education at a local community college and this stuff is facinating to me. My only wish is that i could see a transformer in front of me to actually see points of reference. From you explanation, i understand the principle and theory behind it clearly but seeing where on the transformer the power comes off, and where the neutral take off is, would help me visualize better. Thanks again. Something i wondered for some time but never looked into.

 

[wyliesdiesels]

Freddi,

Thanks for your explanation of split phase/3 phase and why i see 240v single phase as opposing waveforms. I ACTUALLY grasp it all now. The part about what reference is used clearly explains 2 opposing waves, and how its all still single phase in the end.

I work on the low voltage side of the house as a telco field technician so -48v dc is vastly different from this stuff but im doing some continuing education at a local community college and this stuff is facinating to me. My only wish is that i could see a transformer in front of me to actually see points of reference. From you explanation, i understand the principle and theory behind it clearly but seeing where on the transformer the power comes off, and where the neutral take off is, would help me visualize better. Thanks again. Something i wondered for some time but never looked into.

the neutral lug on a transformer is "tapped" or connected to the center of the secondary winding/wire. The hot legs are connected to either end of the secondary winding.

 

[kaffine]

Ground rods have NOTHING to do with ground faults. People commonly confuse EGCs/grounds and grounding electrodes such as rods. Grounding rods are for lightning ONLY! EGCs are for protection from ground faults such as when a winding in a motor shorts to the metal housing which when grounded causes the breaker to trip!

Grounding rods are for more than lightning protection. I will agree that they are not part of the EGC protection. EGC needs a low resistance path back to the source in single phase 240V this would be the neutral coming off the transformer. The low resistance path allows the circuit breaker to trip.

The grounding rod are to make sure the voltages are referenced to a nearby ground. Without the ground rod it would be possible for that voltage level to be much greater. Since insulation can break down with high voltages this is required to make sure the voltage differences stay at a safe level.

 

[toplessHO]

ground rods keep the potential the same thruout the system. This is why they are required to be 5 ohms or less.

 

[kaffine]

ground rods keep the potential the same thruout the system. This is why they are required to be 5 ohms or less.

NEC only requires 25 ohms or less if a single rod is used. If you put 2 rods in NEC doesn't care. In practice this means most just opt to install 2 rods and not worry what the resistance actually is.

 

[Norcal]

ground rods keep the potential the same thruout the system. This is why they are required to be 5 ohms or less.

No NEC requirement for 5 Ohms or less.

 

[wyliesdiesels]

Grounding rods are for more than lightning protection. I will agree that they are not part of the EGC protection. EGC needs a low resistance path back to the source in single phase 240V this would be the neutral coming off the transformer. The low resistance path allows the circuit breaker to trip.

The grounding rod are to make sure the voltages are referenced to a nearby ground. Without the ground rod it would be possible for that voltage level to be much greater. Since insulation can break down with high voltages this is required to make sure the voltage differences stay at a safe level.

Yeah i know that. I shouldnt have used the word ONLY..

 

[ollie76]

So....

I've always been curious about what "ground" and not Neutral, actually refers to here. To me, the fact that "ground" is a rod driven into the ground is coincidental. You're using this rod as a connection to what? Another rod (through the rock and soil) at the transformer pole that has a connection to the source? Power is always trying to return to its source correct? Is just doesn't go randomly into the earth when there's a fault.