250.20(B)(1)

P

Pinnie

Senior Member
Location
Ohio
Occupation
Commercial Electrician
“(1) If the system can be grounded so that the maximum voltage to ground on the ungrounded conductors does not exceed 150 volts”

This is inaccurate wording. The grounding of the system is not what changes a systems voltage to ground. It is the bonding of the earth to the system that achieves this.
 
Not really inaccurate--the word grounding is overloaded and can mean either bonding or earthing. In this sentence, it means earthing.

Cheers, Wayne
 
Pinnie, please allow me to disagree. The word "ground" and its multiple variations generally refer to connections to planet Earth. The word "bond" and its multiple variations generally refer to connecting metal to metal.
 
“Bonded (Bonding). Connected to establish electrical continuity and conductivity. (CMP-5)”

“Grounded (Grounding). Connected (connecting) to ground or to a conductive body that extends the ground connection. (CMP-5)”

“Ground. The earth. (CMP-5)”
wwhitney said:
Not really inaccurate--the word grounding is overloaded and can mean either bonding or earthing. In this sentence, it means earthing.

Cheers, Wayne
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Thank you for your response Wayne. I think we should try to unravel that. I agree it’s used that way, but it’s confusing for people coming into the trade. The definitions matter
charlie b said:
Pinnie, please allow me to disagree. The word "ground" and its multiple variations generally refer to connections to planet Earth. The word "bond" and its multiple variations generally refer to connecting metal to metal.
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Thank you for your response Charlie. I think terms get thrown around too loosely. I think they are used incorrectly often as well.
 
This is another case where "earthing" should have been used over the word "grounding"
 
Pinnie said:
Thank you for your response Charlie. I think terms get thrown around too loosely. I think they are used incorrectly often as well.
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Of course this is the NEC. There are probably a hundred places in the code where the word grounding is used when it should be the word bonding. There have been hundreds of attempts to re-write this but every PI has failed to sway the CMP.
 
infinity said:
Of course this is the NEC. There are probably a hundred places in the code where the word grounding is used when it should be the word bonding. There have been hundreds of attempts to re-write this but every PI has failed to sway the CMP.
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Thank you for your response Rob. This is what I’m saying. I know there was some debate of calling egc equipment bonding conductor at one point (which is hard because it does do both). This confusing is what causes people to thing current flows to ground and think ground rods can clear faults. My 4th year NCCER teacher thought this was the case. It’s gotten people killed. Plus we need young people to come into the trade or we’re over a barrel. (Probably are as it is anyway but we should try).
 
The problem is not the words chosen by the NEC at the time of its creating. The problem is how we use the words now. We tend to use a single, often the primary, definition of a word and not all of its other meanings like the NEC does.

I agree the word Grounding in the NEC should be changed. But it is what it is and we need to keep our minds flexible as to other meanings. This is why the NEC is not for untrained individuals.
 
jim dungar said:
The problem is not the words chosen by the NEC at the time of its creating. The problem is how we use the words now. We tend to use a single, often the primary, definition of a word and not all of its other meanings like the NEC does.

I agree the word Grounding in the NEC should be changed. But it is what it is and we need to keep our minds flexible as to other meanings. This is why the NEC is not for untrained individuals.
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Thank you for your response Jim. IMHO we should strive to simply complicated ideas, especially for guys in the field. It is not often where I work for the NEC, the book itself, to be used at all. We get lucky if somebody wires a three way correctly. It’s a big 180, but “ground” should not also mean “effective fault current path”.
 
Pinnie said:
Thank you for your response Jim. IMHO we should strive to simply complicated ideas, especially for guys in the field. It is not often where I work for the NEC, the book itself, to be used at all. We get lucky if somebody wires a three way correctly. It’s a big 180, but “ground” should not also mean “effective fault current path”.
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In the NEC "ground
does not also mean "effective ground fault current path". Terms that include the word grounding, such as Equipment Ground Conductor, or terms that include bonding, such as Main Bonding Jumper, System Bonding Jumper, and Supply Side Bonding Jumper, do mean effective ground fault current path.
The term "ground" by itself has no meaning in the NEC.

As others have said there have been many attempts to make changes in Article 250, and it has vastly improved over the past 10 code cycles or so. There is room for additional improvement, but there is also a need for much better training for those who use the NEC.

The process to submit Public Inputs to change the code is easy, and the system should open up late this year or early next year for the submission of Public Inputs to make changes in the 2029 code.
 
don_resqcapt19 said:
In the NEC "ground
does not also mean "effective ground fault current path".
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Thank your for your response Don. I was implying is they are confused in practice. In the code rule I referenced, the term is misused in a defined sense.
don_resqcapt19 said:
The term "ground" by itself has no meaning in the NEC.
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It is a defined term.
don_resqcapt19 said:
As others have said there have been many attempts to make changes in Article 250, and it has vastly improved over the past 10 code cycles or so. There is room for additional improvement, but there is also a need for much better training for those who use the NEC.
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I’m not trying to be critical. I know you guys work very hard and are very passionate. Thank you for all the hard work you guys do.
don_resqcapt19 said:
The process to submit Public Inputs to change the code is easy, and the system should open up late this year or early next year for the submission of Public Inputs to make changes in the 2029 code.
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Maybe I will thanks for the tip.
 
Not seeing any issue with the wording in 250.20(B)(1). If we used the definitions of "ground" and "grounded" in post 4, and substitute those into 250.20(B)(1), we get:

If the system can be connected to the earth (or to a conductive body that extends the earth connection) so that the maximum voltage to the earth on the ungrounded conductors does not exceed 150 volts.

Which is fine.

Cheers, Wayne
 
wwhitney said:
If the system can be connected to the earth (or to a conductive body that extends the earth connection) so that the maximum voltage to the earth on the ungrounded conductors does not exceed 150 volts.
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Thank you for your response Wayne. My issue is that the code is saying the grounding of the system is what limits the voltage. The connection of the system to earth never changes the voltage of the ungrounded conductors to ground to be 120v. That comes from the utilization of a neutral point, IMHO.
 
Pinnie said:
The connection of the system to earth never changes the voltage of the ungrounded conductors to ground to be 120v. That comes from the utilization of a neutral point, IMHO.
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Well, I see a slight contradiction in what you just said.

Yes, the "connection of the system to earth" IS what sets "the voltage of the ungrounded conductors to ground to be 120v."

What is constant regardless of an earth connection is the voltage between the ungrounded conductor(s) and the neutral point.

Intentionally earthing that neutral point is what firmly sets the line-to-"ground" voltage.
 
Pinnie said:
My issue is that the code is saying the grounding of the system is what limits the voltage. The connection of the system to earth never changes the voltage of the ungrounded conductors to ground to be 120v.
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Sure it does. When you connect one circuit conductor (usually a neutral) to earth, then the other circuit conductors get a defined voltage to earth (equal to the defined voltage from them to the earthed circuit conductor). So if it's a 208Y/120V system, and you connect the neutral conductor to earth, then the ungrounded conductors are all 120V to earth.

Cheers, Wayne
 
Pinnie said:
?
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computer operator error.

I wanted to say that other than references to voltage two ground, requirements for physical clearance to ground, some references in Chapter 8 that require protective devices to be connected to ground, I can't think of any rules that use the term "ground" by itself. It is almost always combined with other language that provide more information what the rule is about.
There may be some obscure rules that use ground by itself, but can't think of any and don't want to do a word search because LinK does not let me isolate just the word "ground". The results include things like "ground-fault" so there would be a lot of text to scroll through.
 
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