25 Ohm Rule

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George Stolz

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Staff member
Do you think they'll reconsider? :D

Here was my reply to their rejection (essentially) of my suggestion to delete the 25 ohm rule (250.56)

There was no technical substantiation in the panel’s comment to support how a second ground rod improves an electrical grounding system. Moving the text around the code does not distract this section’s legion of critics from the fact that 30 ohms of resistance to earth is likely better than two paths of 3,000,000 ohms. If you move it around, we’ll simply see you next cycle. The proposed changes make absolutely no difference in the interpretation or application of the text, add no additional safety to the NEC, and nothing substantive has been changed. I salute the panel’s tenacity in their defense of this relic, hopefully in time it will fade along with the bygone 3-ohm water pipe requirement. I’m younger than most of you, chances are I’ll outlive you, and perhaps the next generation will be able to demonstrate an enhanced ability to add.
 

480sparky

Senior Member
How to Make Friends and Influence Your Enemies, by George Stolz. Available at bookstores everywhere. :D
 

Pierre C Belarge

Senior Member
I think they should require 25 Ohms to be acheived and not allow for the easy way out drive 2 rods and don't worry about it.

I am curious why you think this would make a difference for the average installation, such as houses, small commercial, etc....


How to Make Friends and Influence Your Enemies, by George Stolz. Available at bookstores everywhere. :D

George
I know a few of the CMPs pretty well, they may get a good chuckle from this. :)
 

zog

Senior Member
I am curious why you think this would make a difference for the average installation, such as houses, small commercial, etc....
It dosent at all, I just like pushing Georges button, you know the big red one that says "25 Ohms", I was hoping to get him riled up (and iwire too)
 

iMuse97

Senior Member
George, you have such a nice way of telling educated people that

they did not previously make sense,
do not now make sense,
and will not ever actually make sense,

if the only thing they do is adjust the location of their nonsense. :)
 

TOOL_5150

Senior Member
George, you have such a nice way of telling educated people that

they did not previously make sense,
do not now make sense,
and will not ever actually make sense,

if the only thing they do is adjust the location of their nonsense. :)
LOL very well put!

Here in CA, ground rods are overrated:D

~Matt
 

iwire

Moderator
Staff member
It dosent at all, I just like pushing Georges button, you know the big red one that says "25 Ohms", I was hoping to get him riled up (and iwire too)
Why I ought to ....:mad:



Thats it buddy your out of here ..... it's a life time ban for you!







:grin:
 

George Stolz

Moderator
Staff member
George, you have such a nice way of telling...
I wouldn't say that was a nice way of telling.

I figured they might listen to reason if you tape it to a rock and hit them in the head with it - vinegar might work where sugar failed. :)

I read it aloud to my fiance, her eyes got big and she said, "Are you ever going to have to work with these people ever again?"

"I don't work with them now, they are the people that write the code. They can't really touch me."

"You can burn a lot of bridges with that."

As I see it, they basically reject at least 50% of everything that comes their way that makes sense (grounding & bonding terms, the permissive NEC doctrine, etc), so rain on them. They can feel angry, laugh, or whatever they want. I hope they spend a minute and review their stances on it.
 

charlie b

Moderator
Staff member
I'd like to look up the proposal and the CMP's reason for rejection. Can you give me the proposal number?
 

tom baker

First Chief Moderator
Staff member
What we need to know is why 25 ohms?
I can explain easily why 6 feet and why two ground rods.
But not a clue about 25 ohms.
Knowing why would help determine if the rule is still required.
 

rbalex

Moderator
Staff member
What we need to know is why 25 ohms?
I can explain easily why 6 feet and why two ground rods.
But not a clue about 25 ohms.
Knowing why would help determine if the rule is still required.
I do have a theory; it has nothing to do with safety. It probably has nothing to do with the original reason any longer either.

For well over 50 years CMP5 and its predecessors were dominated by various telecom interests. In the "early days", "grounding" (the actual connection to earth) had a dramatic effect on signal quality. It isn't nearly as big a deal now, but no one knows why it was a big deal originally either - which is why we never get a solid reason for maintaining it. Sorta like 42 circuits max in a panel.

Of course, this is only a theory.
 

bkludecke

Senior Member
I'm working with a colleague on an article to be published in IAEI magazine about this whole 25 ohm thing. All we are finding is dead ends. It first appeared in the NEC in 1917 but there is no substantiation there either.

The other thing that bugs me is that their is no direction as to how the 25 ohms is measured or maintained. 3rd party? Type of measuring equipment? Time of year?
 

charlie b

Moderator
Staff member
I'd like to look up the proposal and the CMP's reason for rejection. Can you give me the proposal number?
Never mind. I found it. It is item 5-169a. I just submitted the following comment:
Supplemental Electrode Required: A rod, pipe or plate electrode shall not by itself comprise an entire grounding electrode system, but rather shall be supplemented . . . .
My substantiation:
The CMP is incorrectly interpreting its own words, in believing that the wording of this proposal does not presently require a rod to be supplemented, even if the rod is but one electrode in a system comprising many other types of electrodes. The wording, both as originally written in 250.56 and as proposed in 250.53, says that if there is a rod, then it gets supplemented. It says nothing about checking for the presence of other types of electrodes before deciding that a supplemental electrode is required.
Without actually saying so, I just invoked ?Charlie?s Rule? on the CMP. :D
 

cadpoint

Senior Member
Charlie’s Rule of Technical Reading

It doesn’t say what you think it says, nor what you remember it to have said, nor what you were told that it says, and certainly not what you want it to say, and if by chance you are its author, it doesn’t say what you intended it to say. Then what does it say? It says what it says. So if you want to know what it says, stop trying to remember what it says, and don’t ask anyone else. Go back and read it, and pay attention as though you were reading it for the first time.
This is for all you playing along at home that haven't read of know of it: "Charlie's Rule"

I started laughing out loud when I read your closing statements , Charlie B...

George:

I have to say that it read to me like a personal response and not a technical response. oh well maybe next code cycle...
 

zog

Senior Member
The other thing that bugs me is that their is no direction as to how the 25 ohms is measured or maintained. 3rd party? Type of measuring equipment? Time of year?

The only relaible method is the 3 or 4 point fall of potential test. Some will argue the clamp on method works but independent studies have shown this method to be questionable at best, mostly due to limited applications and imporper use of the equipment.

So usually a 3rd party is involved, due to lack of equipment and training of those installing such systems. Just driving a 2nd rod seems to be the method of choice to meet this requirement. Cheaper and easier than testing.
 
ROP CMP Comments

ROP CMP Comments

The only relaible method is the 3 or 4 point fall of potential test. Some will argue the clamp on method works but independent studies have shown this method to be questionable at best, mostly due to limited applications and imporper use of the equipment.

So usually a 3rd party is involved, due to lack of equipment and training of those installing such systems. Just driving a 2nd rod seems to be the method of choice to meet this requirement. Cheaper and easier than testing.
Historical Information

The ROP and Panel Comments will include reasons why they agree or disagree with the comments that were submitted.
 
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