Ground Rod Installation

[T.M.Haja Sahib]

Take any typical service, assuming no grounded metal paths to other structures such as a metal water pipe, and disconnect the neutral under load at any point ahead of the service equipment. Now stand barefooted on a damp concrete floor and touch anything bonded to the service ground and tell me there is no rise in potential, if you survive.

Are you addressing Petersonra through me?

 

[jumper]

Are you addressing Petersonra through me?

 

[kwired]

The reason the neutral is earthed second time is that the neutral should be earthed at multiple points along its route from transformer to the service point to reduce the potential rise at the service equipment enclosures and possible rise at the other equipment enclosures inside the residence,should there be a break in the neutral upstream to the service to the residence.

Are you addressing Petersonra through me?

No I am addressing the idea you presented in the quoted post above that the neutral is earthed to reduce rise in potential should there be a break in the service neutral. If that should happen there will be a rise in potential unless you can achieve virtually zero resistance with your grounding electrode system. Can you find me a grounding electrode system that is capable of zero resistance to earth? Electrode system at transformer location would also have to be zero or you will still have voltage potential.

 

[T.M.Haja Sahib]

No I am addressing the idea you presented in the quoted post above that the neutral is earthed to reduce rise in potential should there be a break in the service neutral. If that should happen there will be a rise in potential unless you can achieve virtually zero resistance with your grounding electrode system. Can you find me a grounding electrode system that is capable of zero resistance to earth? Electrode system at transformer location would also have to be zero or you will still have voltage potential.

But first clarify the why of ''assuming no grounded metal paths to other structures such as a metal water pipe'' in your challenge '' Take any typical service, assuming no grounded metal paths to other structures such as a metal water pipe, and disconnect the neutral under load at any point ahead of the service equipment. Now stand barefooted on a damp concrete floor and touch anything bonded to the service ground and tell me there is no rise in potential, if you survive.''

 

[iwire]

Take any typical service, assuming no grounded metal paths to other structures such as a metal water pipe, and disconnect the neutral under load at any point ahead of the service equipment. Now stand barefooted on a damp concrete floor and touch anything bonded to the service ground and tell me there is no rise in potential, if you survive.''

He will be just as dead if there was an electrode connected in your challenge.

With an open service neutral the voltage will rise to dangerous levels on all bonded metal parts with or without grounding electrodes.

 

[T.M.Haja Sahib]

He will be just as dead if there was an electrode connected in your challenge.

With an open service neutral the voltage will rise to dangerous levels on all bonded metal parts with or without grounding electrodes.

Please let me on what basis you arrived at this remarkable conclusion.

My assertion that reduction of touch voltage on reduction of earth resistance is based on 'Standard hand book for electrical engineers by Fink, published by Mc Graw Hill.

 

[George Stolz]

Drive a ground rod and connect it to a 20A breaker. Assume the ground rod is 25 ohms to earth. The breaker will hold, 4.5 amps will flow, and the rod voltage will be 120V. The earth does not decrease the voltage of the rod.

Now, place a lamp between the breaker and the rod. What is the voltage at the rod? Enough to kill, likely close to 120V.

 

[kwired]

But first clarify the why of ''assuming no grounded metal paths to other structures such as a metal water pipe'' in your challenge '' Take any typical service, assuming no grounded metal paths to other structures such as a metal water pipe, and disconnect the neutral under load at any point ahead of the service equipment. Now stand barefooted on a damp concrete floor and touch anything bonded to the service ground and tell me there is no rise in potential, if you survive.''

I said to assume no metal paths to other structures because if you do have these they will be what does save you from a voltage rise on the neutral and bonded grounding system. If you don't have any metal paths to carry the lost neutral and have to depend solely on the earth to carry it you will have a rise of voltage of the neutral over earth or earthed objects.

If you can not see how this works maybe you should try it, but I would suggest doing it with a controlled method including using a meter to check the voltage at the mentioned touch points instead of placing yourself in danger, and only connect loads to the system you are experimenting with that you are willing to possibly destroy.
Make sure the load on the neutral is unbalanced to insure there is current on the neutral you will be disconnecting. The more balanced the neutral the less severe the problem will be.

 

[T.M.Haja Sahib]

Drive a ground rod and connect it to a 20A breaker. Assume the ground rod is 25 ohms to earth. The breaker will hold, 4.5 amps will flow, and the rod voltage will be 120V. The earth does not decrease the voltage of the rod.

Now, place a lamp between the breaker and the rod. What is the voltage at the rod? Enough to kill, likely close to 120V.

Do me a favor.Please furnish the actual or typical earth resistance value of the neutral grounded at the transformer supplying power to the residence.

 

[T.M.Haja Sahib]

I said to assume no metal paths to other structures because if you do have these they will be what does save you from a voltage rise on the neutral and bonded grounding system.

Why this is so?

 

[kwired]

Why this is so?

They are lower resistance than dirt, and are likely connected to the grounded conductor at another service which is eventually connected to the transformer neutral you are supplied from.

 

[T.M.Haja Sahib]

They are lower resistance than dirt, and are likely connected to the grounded conductor at another service which is eventually connected to the transformer neutral you are supplied from.

The broken neutral via the earthed connection could perform in the same way as above.So something is missing.Please see post no.49.Can you furnish the transformer neutral earth resistance value to proceed further?

 

[Volta]

The broken neutral via the earthed connection could perform in the same way as above.So something is missing.Please see post no.49.Can you furnish the transformer neutral earth resistance value to proceed further?

What is it you are calling the "transformer neutral earth resistance value"?

The resistance to ground of the utility's made electrode?

Who knows? We have to make up a figure. Say 40 ohms...

 

[T.M.Haja Sahib]

What is it you are calling the "transformer neutral earth resistance value"?

The resistance to ground of the utility's made electrode?

Who knows? We have to make up a figure. Say 40 ohms...

See post no.37,the sentence of interest reproduced below.

''However, being as in most residences the transformer is out on a pole, and the neutral is earthed there, ..........''

Shall we take the value of the earth resistance of the neutral of the above transformer to be 40 ohms? or Is it possible for you to check up this value with power supply company people?

 

[Volta]

See post no.37,the sentence of interest reproduced below.

''However, being as in most residences the transformer is out on a pole, and the neutral is earthed there, ..........''

Shall we take the value of the earth resistance of the neutral of the above transformer to be 40 ohms? or Is it possible for you to check up this value with power supply company people?

Huh?

 

[kwired]

The broken neutral via the earthed connection could perform in the same way as above.So something is missing.Please see post no.49.Can you furnish the transformer neutral earth resistance value to proceed further?

Not saying the resistance of the grounding electrode will not matter but even if we assume it to be zero you still have the resistance of the grounding electrode at the service location. Lets say it is 10 ohms which would be considered a very good grounding electrode.

Now lets place a 720 watt 120 volt (20 ohm) resistive load from one line to the open neutral that will seek a path via the 10 ohm grounding electrode. You will have 20(load) plus 10(earth) = 30 ohms of resistance with 120 volts applied. Using Ohms law this gives you a current of 4 amps.

This will give you a voltage drop of 80 volts across the 20 ohm load and a voltage drop of 40 volts across the 10 ohm earth path.

Everything bonded to the grounded service conductor will operate at 40 volts above earth ground. There may not be as much voltage in the area very close to the grounding electrode but that area will be very small especially with only 40 volts of drop. If you were to have direct contact to bare skin across this potential you will feel it.

If you have a water pipe grounding electrode and it is continuous to the neighbors place and is also bonded to their service with a 'good neutral' then its resistance will be very low and will become an alternate path with almost no voltage drop, just like the open neutral conductor would be if it were not open.

 

[T.M.Haja Sahib]

Not saying the resistance of the grounding electrode will not matter but even if we assume it to be zero you still have the resistance of the grounding electrode at the service location. Lets say it is 10 ohms which would be considered a very good grounding electrode.

Now lets place a 720 watt 120 volt (20 ohm) resistive load from one line to the open neutral that will seek a path via the 10 ohm grounding electrode. You will have 20(load) plus 10(earth) = 30 ohms of resistance with 120 volts applied. Using Ohms law this gives you a current of 4 amps.

This will give you a voltage drop of 80 volts across the 20 ohm load and a voltage drop of 40 volts across the 10 ohm earth path.

Everything bonded to the grounded service conductor will operate at 40 volts above earth ground. There may not be as much voltage in the area very close to the grounding electrode but that area will be very small especially with only 40 volts of drop. If you were to have direct contact to bare skin across this potential you will feel it.

If you have a water pipe grounding electrode and it is continuous to the neighbors place and is also bonded to their service with a 'good neutral' then its resistance will be very low and will become an alternate path with almost no voltage drop, just like the open neutral conductor would be if it were not open.

Unfortunately there is mistake in your reasoning.Since the neutral is broken and the earth resistance of the neutral at the residence side is assumed to be zero,everything bonded to the grounded service conductor will operate at 0 volts above earth ground on the residence side.So where is the catch?

 

[T.M.Haja Sahib]

Huh?

 

[iwire]

Please let me on what basis you arrived at this remarkable conclusion.

Basic ohms law.

My assertion that reduction of touch voltage on reduction of earth resistance is based on 'Standard hand book for electrical engineers by Fink, published by Mc Graw Hill.

Your assertion is wrong.

 

[iwire]

Here is a goofy looking but great example of what an electrode cannot accomplish.