RETURN PATH IN LAY-MANS'

[VALZ]

Hello,

I have searched all over this site and the internet for this question to be put in lay-mans’ terms so I can explain it easier to other people. If anyone could help it would be greatly appreciated. The neutral is considered a current carrying conductor, check. Ideal neutral is 0V, check. The neutral is “almost always” bonded to earth. When the “hot” conductor goes through a resistance i.e. light bulb, and there is “extra” voltage that is not being used by R1, it returns safely on the neutral and is dissipated to earth etc…. The question is, if the voltage returns on the BONDED earth neutral why does it not go to a ground fault situation through R1 and back to shut the source breaker off. In other words; If you jump a wire hot to ground you get pop and glow. If the neutral is effectively seeing the same potential as the ground wire “at some point” why does it not pop and glow every time you connect any circuit.

Thank you all for any responses.

 

[ActionDave]

You have it right except for two things.....
The current on the neutral does not go into the earth, it goes back to the transformer.

The equipment ground has to be at the same potential as the neutral for current to flow on it. It is an "extra neutral", but the only time it has any current flowing on it is during a fault and since there are no loads/resistance tons of current flows and trips the breaker.

 

[infinity]

Hello,

The neutral is considered a current carrying conductor, check. Yes

Ideal neutral is 0V, check. Measuring to ground

The neutral is “almost always” bonded to earth. A grounded conductor is required to be grounded which means at some point connected to the earth.

When the “hot” conductor goes through a resistance i.e. light bulb, and there is “extra” voltage that is not being used by R1, it returns safely on the neutral and is dissipated to earth etc…. There is no "extra voltage" and under normal conditions there should be nothing that is dissipated through the earth.

The question is, if the voltage returns on the BONDED earth neutral why does it not go to a ground fault situation through R1 and back to shut the source breaker off. In other words; If you jump a wire hot to ground you get pop and glow. If the neutral is effectively seeing the same potential as the ground wire “at some point” why does it not pop and glow every time you connect any circuit. Because it's connected to a load. If the resistance of the load is low enough the current level may exceed the rating of the OCPD and it will open.

Thank you all for any responses.

I've answered within your post.

 

[iwire]

I will chime in with pointing out with AC the neutral is no more of a return path than the hot conductor.

They both switch functions 60 times a second.

 

[infinity]

I will chime in with pointing out with AC the neutral is no more of a return path than the hot conductor.

They both switch functions 60 times a second.

Good point, one would do best to erase the entire thought of a "return path" from their brain.

 

[mkgrady]

Good point, one would do best to erase the entire thought of a "return path" from their brain.

I struggle to explain to those that want it explained. I'm sometimes asked " if you already have a hot wire, to say a light bulb, why does it also need a neutral? The easy answer seems to be to call it a "return". No idea how to explain it better

 

[GoldDigger]

Independent of the direction of electron movement at any moment of time, I am perfectly happy to designate the hot conductor as supply and the neutral or other grounded conductor as return
If carried to the extreme your position would argue that 120 times a second neither conductor is either supply or return.
An interesting word exercise, but of little practical value, IMHO.

 

[iwire]

Independent of the direction of electron movement at any moment of time, I am perfectly happy to designate the hot conductor as supply and the neutral or other grounded conductor as return

I see no benefit of designating one a supply or return. They are simply circuit conductors, some are grounded some are not.

To each their own.

 

[Haji]

I struggle to explain to those that want it explained. I'm sometimes asked " if you already have a hot wire, to say a light bulb, why does it also need a neutral? The easy answer seems to be to call it a "return". No idea how to explain it better

You may explain with, say, an ammeter. For (RMS) current, phase is the supply conductor and neutral is the return conductor, because if one terminal of the ammeter is connected to phase through a load , current flows when the other terminal is connected to ground. But no current flows when one of its terminal is connected to neutral through a load or not and other to ground.

 

[jaggedben]

What's ironic is that 'return' makes the most sense in DC applications, and in particular electronics, and yet electronics people have a habit of calling the return 'ground.'

:slaphead:

 

[al hildenbrand]

Hello,

Welcome to the Forum!

I have searched all over this site and the internet for this question to be put in lay-mans’ terms so I can explain it easier to other people. If anyone could help it would be greatly appreciated. The neutral is considered a current carrying conductor, check. Ideal neutral is 0V, check. The neutral is “almost always” bonded to earth.

Nicely summarized.

When the “hot” conductor goes through a resistance i.e. light bulb, and there is “extra” voltage that is not being used by R1,

Here's where there are some definitions that need refreshing. " 'extra' voltage that is not being used by R1" must be unpacked and re-stated correctly. Power is used in R1, power that is equal to the voltage from one side of R1 to the other side (the "voltage drop across the load R1") multiplied by the current passing through R1. There is no unused, or "extra", voltage. . . . or power, for that matter. . . . only the power that is used in R1 (it will be electrical energy {power - not voltage} that is turned into light, or heat, or motion, or electronic function).

it returns safely on the neutral and is dissipated to earth etc….

The "extra" voltage, is "the current" (not voltage) and it is NOT dissipated to earth. It, the current, must flow back to the Source it came from, which in a typical residential dwelling, is the secondary winding of the power company transformer that the current left from on the "hot" conductor. The current, returning from R1, will split into a couple currents at the point of the neutral bond to Earth and some of the current will travel in the Earth to the transformer secondary, but most of the current from R1 will travel back to the source, the transformer secondary, on the service drop (or lateral) grounded conductor (neutral).

The question is, if the voltage returns on the BONDED earth neutral why does it not go to a ground fault situation through R1 and back to shut the source breaker off. In other words; If you jump a wire hot to ground you get pop and glow. If the neutral is effectively seeing the same potential as the ground wire “at some point” why does it not pop and glow every time you connect any circuit.

Thank you all for any responses.

Although you state this as your question, back up to the points about voltage, current, and power, first and then reconsider the question. It seems to me you are missing the place and function of current in relation to the change of power from electric energy to other forms of energy.

 

[VALZ]

THANK YOU TO ALL!

THANK YOU TO ALL!

I sincerely appreciate all of your input to this question and how it was broken down. BEST electrical site on the internet hands down!

 

[Strathead]

I struggle to explain to those that want it explained. I'm sometimes asked " if you already have a hot wire, to say a light bulb, why does it also need a neutral? The easy answer seems to be to call it a "return". No idea how to explain it better

I hadn't really thought this before, but as iwire is right, I just though of a better concept for the question you asked. "To complete the loop." Regardless of which direction you go, you have to get back to where you started from.

 

[Strathead]

Hello,

I have searched all over this site and the internet for this question to be put in lay-mans’ terms so I can explain it easier to other people. If anyone could help it would be greatly appreciated. The neutral is considered a current carrying conductor, check. Ideal neutral is 0V, check. The neutral is “almost always” bonded to earth. When the “hot” conductor goes through a resistance i.e. light bulb, and there is “extra” voltage that is not being used by R1, it returns safely on the neutral and is dissipated to earth etc…. The question is, if the voltage returns on the BONDED earth neutral why does it not go to a ground fault situation through R1 and back to shut the source breaker off. In other words; If you jump a wire hot to ground you get pop and glow. If the neutral is effectively seeing the same potential as the ground wire “at some point” why does it not pop and glow every time you connect any circuit.

Thank you all for any responses.

My take:

I think others are avoiding this, but the neutral is only a current carrying conductor sometimes. You can assume that it usually carries some current when current is flowing, but for the sake of gaining expertise, don't say "current carrying conductor" More on this as you grow and learn.

The "extra voltage" touched on by others. Voltage is pressure, either it is used or it isn't. Water is often an easier way for a layman's brain to "see". If you have pressurized water in a large pipe and it splits up to three faucets, each faucet has the same amount of pressure at it, and as long as the pipe size (which equals resistance) is large enough that pressure will relatively equal the supply pressure. After it comes out of the faucet it has no pressure and you can think of the neutral as a drain pipe that returns the water to the source. (as stated this is not accurate, but gives a better visual concept). If you were to put an impeller in the pipe that drives a wheel, for example, but then had the water continue on to another impeller and finally out of a faucet, to return to the source, each impeller, would share some of the pressure, and then the faucet would "use up" the last of the pressure, again zero pressure in the drain. In this Each impeller uses some pressure (equals voltage) determined by it opposition (resistance) to the flow (current) of the water, to move the wheel (work or wattage). More work means more opposition, means more reduction in flow, means a larger portion of the available pressure (again voltage). Reduce the starting pressure, reduce the amount of work each does, but not the share of the pressure that each uses. But in all scenarios, the open faucet still uses the last of the pressure available. This isn't perfect, but it is as close as you can get and still be able to visualize, as water can be seen electron, or holes or waves, whichever theory is currently (no pun intended) in vogue can not be seen. So, no extra voltage.


Last thing for now. A big difference with water, is the basic need (again not entirely factual but good enough) for the system to be "closed". Think of electricity or more accurately one piece or bit of the energy, (i.e. electron) as needing to start at one point, travel wherever it is going to go, and then finding its way BACK to the starting point. With the proverbial kick in the butt from the generator (as in item that generates). Ideally the electron will find its way back on the wire paths we intend it to use, but when that path is not available, we want to give the electron the ability to get back anyway, otherwise it will just sit there until you or someone else, completes that path between it and the source it has to get back to. Then you become the path. That is the sole reason we have grounding. So that the electrons can get back without causing damage to other equipment and people. That "extra" path isn't needed for the electricity to operate and in fact is not done sometimes. Specifically on military vessels, where they would rather have voltage potential and weapons that still work and the possibility that a sailor gets electrocuted than a tripped breaker that means the torpedo won't fire. In those cases they have warning lights that notify of the problem instead.

 

[kwired]

My take:

I think others are avoiding this, but the neutral is only a current carrying conductor sometimes. You can assume that it usually carries some current when current is flowing, but for the sake of gaining expertise, don't say "current carrying conductor" More on this as you grow and learn.

The "extra voltage" touched on by others. Voltage is pressure, either it is used or it isn't. Water is often an easier way for a layman's brain to "see". If you have pressurized water in a large pipe and it splits up to three faucets, each faucet has the same amount of pressure at it, and as long as the pipe size (which equals resistance) is large enough that pressure will relatively equal the supply pressure. After it comes out of the faucet it has no pressure and you can think of the neutral as a drain pipe that returns the water to the source. (as stated this is not accurate, but gives a better visual concept). If you were to put an impeller in the pipe that drives a wheel, for example, but then had the water continue on to another impeller and finally out of a faucet, to return to the source, each impeller, would share some of the pressure, and then the faucet would "use up" the last of the pressure, again zero pressure in the drain. In this Each impeller uses some pressure (equals voltage) determined by it opposition (resistance) to the flow (current) of the water, to move the wheel (work or wattage). More work means more opposition, means more reduction in flow, means a larger portion of the available pressure (again voltage). Reduce the starting pressure, reduce the amount of work each does, but not the share of the pressure that each uses. But in all scenarios, the open faucet still uses the last of the pressure available. This isn't perfect, but it is as close as you can get and still be able to visualize, as water can be seen electron, or holes or waves, whichever theory is currently (no pun intended) in vogue can not be seen. So, no extra voltage.


Last thing for now. A big difference with water, is the basic need (again not entirely factual but good enough) for the system to be "closed". Think of electricity or more accurately one piece or bit of the energy, (i.e. electron) as needing to start at one point, travel wherever it is going to go, and then finding its way BACK to the starting point. With the proverbial kick in the butt from the generator (as in item that generates). Ideally the electron will find its way back on the wire paths we intend it to use, but when that path is not available, we want to give the electron the ability to get back anyway, otherwise it will just sit there until you or someone else, completes that path between it and the source it has to get back to. Then you become the path. That is the sole reason we have grounding. So that the electrons can get back without causing damage to other equipment and people. That "extra" path isn't needed for the electricity to operate and in fact is not done sometimes. Specifically on military vessels, where they would rather have voltage potential and weapons that still work and the possibility that a sailor gets electrocuted than a tripped breaker that means the torpedo won't fire. In those cases they have warning lights that notify of the problem instead.

A better analogy then a typical domestic water system may be a hydraulic power system where the media is directly recirculated within the system.

One problem that is still different though is leakage to outside of the system. I guess the equipment ground is sort of a drip pan to collect what leaks, but is designed to collect what can be delivered to it as well as to return it to the source with minimal resistance to flow.

 

[Strathead]

A better analogy then a typical domestic water system may be a hydraulic power system where the media is directly recirculated within the system.

One problem that is still different though is leakage to outside of the system. I guess the equipment ground is sort of a drip pan to collect what leaks, but is designed to collect what can be delivered to it as well as to return it to the source with minimal resistance to flow.

Good point. Nothing is perfect for example there is still some pressure (voltage equal) on the return for hydraulic and almost none in electrical. Even as I type this I know that nitpicky says that all wire has resistance so there is some voltage being accounted for on the return path.

 

[tom baker]

One of the reasons we don't understand G&B is the use of lay-mans terms. the code terms are specific and for the most part OK
Example
I need to pull a ground
The receptacle is not grounded
what size ground for a 200 amp service

Mike Holt once said "what color is it and what does it do?"

Whats not OK is the term EGC. But that's a different story.

 

[ActionDave]

Whats not OK is the term EGC. But that's a different story.

I can think of no better term than Equipment Grounding Conductor. If I use it you know exactly what I am talking about.

 

[jumper]

I can think of no better term than Equipment Grounding Conductor. If I use it you know exactly what I am talking about.

I like Equipment Bonding Conductor a whole lot better, but it is already taken.

 

[big john]

I struggle to explain to those that want it explained. I'm sometimes asked " if you already have a hot wire, to say a light bulb, why does it also need a neutral? The easy answer seems to be to call it a "return". No idea how to explain it better

The best example I know to give is to explain that you can have a 120V ungrounded transformer: In that case there is no "neutral" and yet the bulb still works just the same.

All that happens when you ground one conductor is you are putting it at the same potential when measured against the earth and painting it white. It still works the same way it did before.

I think the NEC would be a world better if we removed every reference to and iteration of the word "ground." Stick with "earthed" and "bonded."