Current on Grounded Conductor

[DBoone]

A friend of mine does not believe that the grounded conductor carries current. I have tried to explain to him a several occasions that it does in fact carry current and how the "neutral" on a 2 wire 120v circuit carries the same current as the "hot" but all of my attempts to convince him have not worked. He is set on the thought that the "neutral" does not have any current on it. He says "if it had current on it people would be getting shocked and possibly killed everytime they touched a meter, panel, etc. Even if I put my clamp meter on the "neutral" and showed him that it read current I still believe he would have some explanation. So, seeing as how I'm relatively new to the field and I can't seem to find the proper words to give him a clear understanding, could you professionals put into layman's terms why we do not get a shock from a properly installed "neutral" and what scenarios would cause the "neutral" to become a shock hazard and potential life ender. Thanks!

 

[kwired]

A friend of mine does not believe that the grounded conductor carries current. I have tried to explain to him a several occasions that it does in fact carry current and how the "neutral" on a 2 wire 120v circuit carries the same current as the "hot" but all of my attempts to convince him have not worked. He is set on the thought that the "neutral" does not have any current on it. He says "if it had current on it people would be getting shocked and possibly killed everytime they touched a meter, panel, etc. Even if I put my clamp meter on the "neutral" and showed him that it read current I still believe he would have some explanation. So, seeing as how I'm relatively new to the field and I can't seem to find the proper words to give him a clear understanding, could you professionals put into layman's terms why we do not get a shock from a properly installed "neutral" and what scenarios would cause the "neutral" to become a shock hazard and potential life ender. Thanks!

There is current in that conductor.

Start your explanation/demonstration with this: Open circuit the grounded conductor, current will stop flowing and the load will stop working. You will also measure full voltage from the opened circuit to ground, and will definitely feel shock if you make yourself part of the circuit. Use a simple incandescant lamp as the load and do not use a multiwire circuit, there are other complexities with those, but the concepts of the simple circuit need learned first.

 

[cadpoint]

How's you math? On a multi-wire circuit two hot circuits can share a neutral.

Put a 1500W hair drier on one circuit and a 200W lamp on the other circuit. The shared neutral will carry the imbalance of the two loads.

P=IE 1500/120 =10 Amps

P=IE 200/120= 1.67 Amps

10-1.67=8.33 Amps

 

[suemarkp]

Have him touch the +12V terminal on a car battery while you crank the engine. Lots of current there, no shock. Have him touch a spark plug wire -- lots of voltage there and low current.

There needs to be a certain voltage to ground for you to feel it, and current flow in the wire isn't too relevant. The grounded conductor is typically a few volts above ground, so you don't get shocked. It is not equal to ground because of the voltage drop in the wire. Perhaps measure the N-G voltageon a circuit with a heavy load and compare it to no load, then may be he'll see. That's the voltage drop on the neutral.

 

[kwired]

Have him touch the +12V terminal on a car battery while you crank the engine. Lots of current there, no shock. Have him touch a spark plug wire -- lots of voltage there and low current.

There needs to be a certain voltage to ground for you to feel it, and current flow in the wire isn't too relevant. The grounded conductor is typically a few volts above ground, so you don't get shocked. It is not equal to ground because of the voltage drop in the wire. Perhaps measure the N-G voltageon a circuit with a heavy load and compare it to no load, then may be he'll see. That's the voltage drop on the neutral.

Though what you say is true it is not exactly what the OP's friend is missing out on (yet). He has the impression there is no current flowing on the grounded conductor, and you need to prove there is current flowing here before the concepts you introduced will even begin to sink in.

 

[electrofelon]

You might also point out kirchoffs laws. Using the current law will prove that there is equal current regardless of where in the circuit you are. Then you could use the voltage law and a little sketch to show how the voltage to ground/one side of the circuit decreases continually (but mostly after the load) as you traverse the circuit which will explain why you generally dont get shocked from a grounded conductor.

For a more physical explanation, use the water analogy and ask where those electrons are disappearing to?

 

[97catintenn]

Ask him to explain how a GFCI trips.

 

[kwired]

You might also point out kirchoffs laws. Using the current law will prove that there is equal current regardless of where in the circuit you are. Then you could use the voltage law and a little sketch to show how the voltage to ground/one side of the circuit decreases continually (but mostly after the load) as you traverse the circuit which will explain why you generally dont get shocked from a grounded conductor.

For a more physical explanation, use the water analogy and ask where those electrons are disappearing to?

Yes start with the theory lecture, then move to the lab (my practical application in earlier post) and prove the theory is correct.

Ask him to explain how a GFCI trips.

You have to understand that current is flowing on the neutral first, or the GFCI will always be a mystery, or at least totally misunderstood. There are still many that think a GFCI is some kind of circuit breaker, and have no clue that there are circuit breakers that have extra features (the GFCI circuit breaker).

 

[roger]

To go along with the others explanations show him this simple illustration.

Roger

 

[Lectricbota]

What I have found out with something like this is to start from the basics. People that have no clue about electricity are sometimes shocked that electricity isn't made, that it's just a transfer of energy.
Once they figure out electron flow and things of that nature it becomes a lot clearer.

 

[GoldDigger]

To go along with the others explanations show him this simple illustration.

Roger

The comment about the grounded conductor not being a neutral in the illustration is somewhat misleading, and actually supports a mistaken belief that the reason that it is not a neutral is that it is carrying current.

IIRC the definition of "neutral" is a conductor which has the same voltage difference to all of the phase conductors, regardless of what the potential of that conductor itself it.

It is confusing to try apply that definition to a 120 volt-only service, but what we conventionally refer to as the neutral does have the same potential difference to all (one) of the phase conductors.
By that same argument, though, the hot wire is also a neutral.

In a straight three wire three-phase delta secondary, there is not a neutral wire. From a three phase wye secondary, there is a neutral, even it is not connected to anything.

The fundamental problem in the friend's view of the situation may be that he thinks that you can have a unidirectional flow of current to a load, without any return path, just as you can have water flowing through a hose (the old analogy getting overstressed) without having a closed loop of hose.

 

[roger]

The comment about the grounded conductor not being a neutral in the illustration is somewhat misleading, and actually supports a mistaken belief that the reason that it is not a neutral is that it is carrying current.

Actually the only thing misleading is incorrect definitions. In the illustration you have a series circuit with the same current through out the circuit so there is no imbalanced current on either conductor.

I know what the NEC definition is and in reality a neutral can only exist if there are more than two conductors in a circuit. We can call it a neutral because it is connected to the neutral point of a winding but that is only because someone decided to.

Roger

 

[kwired]

The comment about the grounded conductor not being a neutral in the illustration is somewhat misleading, and actually supports a mistaken belief that the reason that it is not a neutral is that it is carrying current.

IIRC the definition of "neutral" is a conductor which has the same voltage difference to all of the phase conductors, regardless of what the potential of that conductor itself it.

It is confusing to try apply that definition to a 120 volt-only service, but what we conventionally refer to as the neutral does have the same potential difference to all (one) of the phase conductors.
By that same argument, though, the hot wire is also a neutral.

In a straight three wire three-phase delta secondary, there is not a neutral wire. From a three phase wye secondary, there is a neutral, even it is not connected to anything.

The fundamental problem in the friend's view of the situation may be that he thinks that you can have a unidirectional flow of current to a load, without any return path, just as you can have water flowing through a hose (the old analogy getting overstressed) without having a closed loop of hose.

The neutral in that case is neutral to the source not the connected branch circuit. There is nothing neutral in the branch circuit itself.

And if you had an open conductor with electrons pouring out on the ground (like a hose with water) you better watch out where you step, don't want to come into contact with the pile of electrons there, and it is tricky because they are too small to see

 

[charlie b]

Are you sure that your friend is not confusing the grounded conductor with the equipment grounding conductor?

 

[DBoone]

Charlie B, I'm positive he is referring to the grounded conductor. He seems to have his own theory that electrons get excited and alternate directions just on the ungrounded conductor. When I try to explain otherwise he usually says "you're letting some nuts on the Internet make you think there is current on this wire (grounded conductor) and there isn't. Etc etc etc. He also is stuck on the thought that the electrons are trying to go to the ground and not back to the source. Again he has his own theory that once they get to the earth they are satisfied. To the poster that mentioned the GFCI, I've had that same thought myself and the next time I get into a debate with him I am going to bring it up. Thank you all for great responses. I hope to convince him one day and in the mean time I will continue to soak up as much knowledge from you all as I can. Thanks.

 

[petersonra]

I had an electrician one time explain to me that the reason the neutral side of a plug is bigger is because there is more current there.

A guy just yesterday who claims to be some kind of navy electrician told me he always ungrounds his power because it is safer to work on ungrounded power when standing in water.

 

[DBoone]

I forgot to add one thing, whenever we debate it he always goes for the "it's called electrical THEORY, nobody really knows how electricity works"...frustrating.

 

[hardworkingstiff]

I had an electrician one time explain to me that the reason the neutral side of a plug is bigger is because there is more current there.

Wow.

A guy just yesterday who claims to be some kind of navy electrician told me he always ungrounds his power because it is safer to work on ungrounded power when standing in water.

WOW!!!

 

[don_resqcapt19]

...WOW!!!

While not being safe, it is safer to work on ungrounded electrical system while standing in water than to work on grounded electrical systems under the same conditions.

 

[don_resqcapt19]

I forgot to add one thing, whenever we debate it he always goes for the "it's called electrical THEORY, nobody really knows how electricity works"...frustrating.

If it doesn't carry current, ask him why he installs it? If it doesn't carry current the circuit should work fine without it.