HELLO

[frodo6]

Hello sparkies
I have stopped by because i have a slight problem in my house.
I am a master plumber, I have worked with you guys for years,
I hope you would be so kind as to steer me in the right direction.
when my AC kicks on, my lights blink.
From what I know, that aint good.
I have a 200 amp service so that is not the problem
any guesses as to wth is up?

 

[Megawatt]

But when it is grounded how do you prove that it is grounded with a low enough resistance?
How do you know that there is no damage to cables which are hidden?

I take my meter and measure the incoming neutral wire and rods in the ohms setting and usually it’s less than 1 ohm
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I take my meter and measure the incoming neutral wire and rods in the ohms setting and usually it’s less than 1 ohm

We are talking about really no resistance at all

 

[davesparks]

I take my meter and measure the incoming neutral wire and rods in the ohms setting and usually it’s less than 1 ohm
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We are talking about really no resistance at all

How do you measure the rods? Presumably the direct measurement method using another substantial piece of buried metal?

What is the limit of resistance permitted for your grounds in an installation?

For a circuit breaker or fuse to work properly on a fault then the ground must be of low enough resistance.
The higher the resistance of the ground the slower the circuit breaker will react to the fault.
We have rules on how fast we need a circuit breaker to operate, in the UK this is 0.4seconds for final circuits and 5seconds for distribution circuits (there's more to it than this but I'm keeping it simple here)
So we can calculate the maximum ground resistance permitted to achieve the required disconnection time.

From this we can calculate the size of ground needed and also test it after installation to ensure compliance.

You say we are talking about no resistance at all, but that's not true, every conductor has resistance. The resistances are very small, but so are the limits for correct operation of a circuit breaker.
The limits can be well below 1 ohm and so accurate calibrated testers are needed

 

[Megawatt]

How do you measure the rods? Presumably the direct measurement method using another substantial piece of buried metal?

What is the limit of resistance permitted for your grounds in an installation?

For a circuit breaker or fuse to work properly on a fault then the ground must be of low enough resistance.
The higher the resistance of the ground the slower the circuit breaker will react to the fault.
We have rules on how fast we need a circuit breaker to operate, in the UK this is 0.4seconds for final circuits and 5seconds for distribution circuits (there's more to it than this but I'm keeping it simple here)
So we can calculate the maximum ground resistance permitted to achieve the required disconnection time.

From this we can calculate the size of ground needed and also test it after installation to ensure compliance.

You say we are talking about no resistance at all, but that's not true, every conductor has resistance. The resistances are very small, but so are the limits for correct operation of a circuit breaker.
The limits can be well below 1 ohm and so accurate calibrated testers are needed

Dave it is not letting me post my reply but table 250.102(c)(1) is how we size our grounded conductor we don’t have to run all the test that y’all do. Our house breakers are 10 RMS and they trip less than 1 second. The NEC has done all the calculations that you are talking about. We have to go by the book. Maybe this will post

 

[davesparks]

Dave it is not letting me post my reply but table 250.102(c)(1) is how we size our grounded conductor we don’t have to run all the test that y’all do. Our house breakers are 10 RMS and they trip less than 1 second. The NEC has done all the calculations that you are talking about. We have to go by the book. Maybe this will post

What do you mean by 10RMS?

Surely you are taught the theory and science behind the tables in the book? We also have tables for selecting the size of an earth but we also can calculate it instead. The tables often end up with an earth way bigger than it needs to be.

 

[Megawatt]

Dave it is not letting me post my reply but table 250.102(c)(1) is how we size our grounded conductor we don’t have to run all the test that y’all do. Our house breakers are 10 RMS and they trip less than 1 second. The NEC has done all the calculations that you are talking about. We have to go by the book. Maybe this will post

Dave the US and the UK have different rules and as much as I have read about the way y’all have to do things I’m great full to be in the USA. We have to follow the rules set by the NEC

What do you mean by 10RMS?

Surely you are taught the theory and science behind the tables in the book? We also have tables for selecting the size of an earth but we also can calculate it instead. The tables often end up with an earth way bigger than it needs to be.

RMS is the interruption rating of the breaker
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Dave the US and the UK have different rules and as much as I have read about the way y’all have to do things I’m great full to be in the USA. We have to follow the rules set by the NEC

RMS is the interruption rating of the breaker

You stated that your tables give you a size that in your mind is bigger than you need. I believe that when it comes to grounded conductor I think that it should be the same size as the ungrounded conductors
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Dave the US and the UK have different rules and as much as I have read about the way y’all have to do things I’m great full to be in the USA. We have to follow the rules set by the NEC

RMS is the interruption rating of the breaker
[automerge]1568472930[/automerge]

You stated that your tables give you a size that in your mind is bigger than you need. I believe that when it comes to grounded conductor I think that it should be the same size as the ungrounded conductors

Dave I give up I know you are smarter than me when it comes to the theory of electrical

 

[davesparks]

You stated that your tables give you a size that in your mind is bigger than you need. I believe that when it comes to grounded conductor I think that it should be the same size as the ungrounded conductors

It's not bigger in my mind, it is bigger as is proven by science.

Why do you think that it should be the same size? The science doesn't back this up.

 

[Megawatt]

It's not bigger in my mind, it is bigger as is proven by science.

Why do you think that it should be the same size? The science doesn't back this up.

Harmonics- I believe that eventually the grounded conductor will be the same size as ungrounded conductors. I did not go college like you and sometimes the theory is over my head. Why are you pressing this matter so much, you win you are smarter than me

 

[davesparks]

Harmonics- I believe that eventually the grounded conductor will be the same size as ungrounded conductors. I did not go college like you and sometimes the theory is over my head. Why are you pressing this matter so much, you win you are smarter than me

I'm not pressing the matter, just trying to discuss it.

Now I'm getting confused, you moved from ground to grounded which I understand to be two different things in the USA?

I'm talking about earth wires (ground) where the required size is calculated.

I thought that in the USA grounded conductor is what we call the neutral conductor?

 

[Megawatt]

Harmonics- I believe that eventually the grounded conductor will be the same size as ungrounded conductors. I did not go college like you and sometimes the theory is over my head. Why are you pressing this matter so much, you win you are smarter than me

We have gone way off topic of the original thread, which I would get in trouble w

I'm not pressing the matter, just trying to discuss it.

Now I'm getting confused, you moved from ground to grounded which I understand to be two different things in the USA?

I'm talking about earth wires (ground) where the required size is calculated.

I thought that in the USA grounded conductor is what we call the neutral conductor?

You are right the grounded conductor is what we are talking about not the grounding conductor
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I'm not pressing the matter, just trying to discuss it.

Now I'm getting confused, you moved from ground to grounded which I understand to be two different things in the USA?

I'm talking about earth wires (ground) where the required size is calculated.

I thought that in the USA grounded conductor is what we call the neutral conductor?

I read this whole thread today and I don’t see where I stated grounding instead of grounded
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We have gone way off topic of the original thread, which I would get in trouble w

You are right the grounded conductor is what we are talking about not the grounding conductor
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I read this whole thread today and I don’t see where I stated grounding instead of grounded

I feel like lm in school again and this is making me look bad to all the others in this forum

 

[davesparks]

You are right the grounded conductor is what we are talking about not the grounding conductor

I read this whole thread today and I don’t see where I stated grounding instead of grounded

Then I apologise as I may have confused the issue completely.
Its hard to get used to your use of grounded and grounding as the names for two different conductors. Especially when you talk about connecting the grounded conductor to earth rods.

 

[Megawatt]

Then I apologise as I may have confused the issue completely.
Its hard to get used to your use of grounded and grounding as the names for two different conductors. Especially when you talk about connecting the grounded conductor to earth rods.

Dave I have a 9th grade education and I took ac-dc theory but most of it was over my head. I’ve got the upmost respect for you and your knowledge of the electrical system. I guess the way we do things could be confusing but I know my job and it seems like you are going back to Tesla days which I get lost
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Dave the US and the UK have different rules and as much as I have read about the way y’all have to do things I’m great full to be in the USA. We have to follow the rules set by the NEC

RMS is the interruption rating of the breaker
[automerge]1568472930[/automerge]

You stated that your tables give you a size that in your mind is bigger than you need. I believe that when it comes to grounded conductor I think that it should be the same size as the ungrounded conductors

Dave I give up I know you are smarter than me when it comes to the theory of electrical

Dave the US and the UK have different rules and as much as I have read about the way y’all have to do things I’m great full to be in the USA. We have to follow the rules set by the NEC

RMS is the interruption rating of the breaker
[automerge]1568472930[/automerge]

You stated that your tables give you a size that in your mind is bigger than you need. I believe that when it comes to grounded conductor I think that it should be the same size as the ungrounded conductors
[automerge]1568473100[/automerge]

Dave I give up I know you are smarter than me when it comes to the theory of electrical

Dave I misquoted about the 10 RMS it should be 10k RMS interrupting rating