new definition of grounded

[don_resqcapt19]

Trying,

If you are saying 250-20 applies to ungrounded systems, specifically where does it address ungrounded systems?

Sorry, I didn't look at the book...250.50 tells us what systems must be grounded, 250.21 tells us what systems that are permitted, but not required to be grounded, and 250.22 tells us what ones are not permitted to be grounded. I didn't look and my memory told me that all three parts were in one section...

Quote:
Originally Posted by don_resqcapt19
If 250.20 requires the system to be grounded or if it permits the system to be grounded and the design requires grounding, then we have a problem with the new definition if the system is supplied by a portable generator.

But you say in the end of your post #36 ?There is no conflict between 250-20 and the definition?, what do you mean above?

Because the conflict is not with 250.20, it is with the definition and 250.34 for portable generators.

Where does 250-20 tell me an ungrounded system must be grounded?

It tells us what systems are required to be grounded. All of the commonly used systems are systems that are required to be grounded systems.

The conflict between the definition is because the definition tells us that the only way to have a grounded system is to have a connection to earth and 250.34 says we don't need that connection to earth for a portable generator.
Don

 

[tryinghard]

Don,

Previously I asked in post #40:
Where does 250-20 tell me an ungrounded system must be grounded? And your now answering:

It tells us what systems are required to be grounded. All of the commonly used systems are systems that are required to be grounded systems.

This is what I?m saying in Post #35, ungrounded systems are not controlled by 250-20 only grounded systems, thanks!

 

[jwelectric]

Mike, Under the 2005 code I would have agreed with that, but not with the new defintion.

Good at least we are in agreement with the 2005 cycle so let?s look at the 2008.

Personally I like the new definition of grounded (grounding) as it should put to rest all this debate of equipment grounding and equipment bonding conductors.
We now know that the job of the equipment grounding conductor is to establish a connection to earth.
?Equipment Bonding Conductor? is only found in two articles of the NEC, once in 250.184(B)(5) and again in 408.3(C).

250.20 requires that a 120/240 volt system be a grounded system. With the new definition, the only way to get a grounded system is to make a connection to earth.

It has always been my opinion that this was what the requirement has always been, a connection to earth.

It is my opinion that the new defintion of grounded is in conflict with 250.34 any time you are required to have a grounded system that is supplied by a portable generator.

Don

Here is where I begin to lose you.
If ?you are required to have a grounded system? then the generator will be grounded through that system.
If the portable generator is being used with equipment that is connected to the generator and not a building where a panel is being fed then 250.34 relieves the requirement to connect to earth (ground). All the bonding to the source is done through the frame of the portable generator.
250.34 (C) addresses the ?grounded conductor? bonding and states that it ?shall? be connected to the frame. I would say that the use of the phrase ?grounded conductor? in 250.34(C) is what needs to be addressed and replaced with the new definition ?neutral point?

If this portable generator is being used as a stand alone system with equipment, tools, appliances or what have you, being plugged directly into the generator then this generator is a separately derived system or a stand alone system and will fall under the scope of 250.34 and does not require any connections to earth.
This portable generator would be an ungrounded system.

If this generator is connected to a building with another electrical system then the fate of the grounding of the generator would depend on the type of installation done to the premises wiring.
Using the generator as outlined in 702 although it is still a portable generator the connection to the building would render it fixed unless of course it was connected to a mobile home and then it would still be debatable as to whether it would be portable.

What say yea, Am I confused?

 

[don_resqcapt19]

trying,

This is what I’m saying in Post #35, ungrounded systems are not controlled by 250-20 only grounded systems, thanks!

Ungrounded systems that are permitted to be ungrounded have nothing to do with this thead. This thead is only about systems that are required to be grounded and the change in the definiton of grounded in Article 100.

 

[don_resqcapt19]

Mike,

If this portable generator is being used as a stand alone system with equipment, tools, appliances or what have you, being plugged directly into the generator then this generator is a separately derived system or a stand alone system and will fall under the scope of 250.34 and does not require any connections to earth.
This portable generator would be an ungrounded system

It is my opinion that with the change in the definition of grounded in Article 100 it is no longer possible to supply a power system that is required to be grounded from a portable generator that uses the generator frame as a grounding electrode. The removal of the words "some conducting body that serves in place of the earth" from the definition of grounded makes it impossible to use the generator frame as the grounding electrode no matter what 250.34 says.
Don

 

[jwelectric]

Mike,

It is my opinion that with the change in the definition of grounded in Article 100 it is no longer possible to supply a power system that is required to be grounded from a portable generator that uses the generator frame as a grounding electrode. The removal of the words "some conducting body that serves in place of the earth" from the definition of grounded makes it impossible to use the generator frame as the grounding electrode no matter what 250.34 says.
Don

If a portable generator is being used as a separately derived system for back-up as outlined in Article 702 the grounding would be required to comply with 250.20(D), see Fine Print Note under 250.35(D) Separately Derived Systems which refers to 250.30.
If the generator is not being installed as a separately derived system then the grounding (connection to earth) will take place at the service equipment of the power system being supplied.
If the generator is being used with the receptacles that come with the generator then 250.34(A) relinquishes the requirement to ground or connect to earth. Two rules must be observed, one The generator supplies only equipment mounted on the generator, cord-and-plug-connected equipment through receptacles mounted on the generator, or both, and two, The non?current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are bonded to the generator.
Notice that there is no mention of the equipment grounding conductor for this generator that is being used as a stand alone system. Why? Because there is no equipment grounding conductor being used.
The green conductor in the cords supplying the equipment being used is not an equipment grounding conductor in this case simply because it is not connecting anything to earth. It is this scenario that in my opinion one could rightly call the green wire an equipment bonding conductor.

 

[don_resqcapt19]

Mike,

If the generator is being used with the receptacles that come with the generator then 250.34(A) relinquishes the requirement to ground or connect to earth. Two rules must be observed, one The generator supplies only equipment mounted on the generator, cord-and-plug-connected equipment through receptacles mounted on the generator, or both, and two, The non–current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are bonded to the generator.

This is where I don't agree. It is my opinion that if the supplied circuits are ones that are required to be grounded per 250.20, then the new defintion of grounded requires a connection to earth. Under the 2005 code, the generator frame was permitted to be used as the grounding electrode because the words "some other conductive body that serves in place of the earth" were in the definition of grounded. Now that those words are gone, it is my opinion that 250.34 is no longer valid as there is no way to supply a grounded system without a connection to earth.
Don

 

[jwelectric]

If the generator is being used with the receptacles that come with the generator then 250.34(A) relinquishes the requirement to ground or connect to earth. Two rules must be observed, one The generator supplies only equipment mounted on the generator, cord-and-plug-connected equipment through receptacles mounted on the generator, or both,

Mike, This is where I don't agree. It is my opinion that if the supplied circuits are ones that are required to be grounded per 250.20, then the new defintion of grounded requires a connection to earth. Under the 2005 code, the generator frame was permitted to be used as the grounding electrode because the words "some other conductive body that serves in place of the earth" were in the definition of grounded. Now that those words are gone, it is my opinion that 250.34 is no longer valid as there is no way to supply a grounded system without a connection to earth.
Don

II. System Grounding
250.20 Alternating-Current Systems to Be Grounded.
Alternating-current systems shall be grounded as provided for in 250.20(A), (B), (C), or (D). Other systems shall be permitted to be grounded. If such systems are grounded, they shall comply with the applicable provisions of this article.
(B) Alternating-Current Systems of 50 Volts to 1000 Volts. Alternating-current systems of 50 volts to 1000 volts that supply premises wiring and premises wiring systems shall be grounded under any of the following conditions:
(1) Where the system can be grounded so that the maximum voltage to ground on the ungrounded conductors does not exceed 150 volts
(2) Where the system is 3-phase, 4-wire, wye connected in which the neutral is used as a circuit conductor

Also found under Part II for System Grounding

250.34 Portable and Vehicle-Mounted Generators.
(A) Portable Generators. The frame of a portable generator shall not be required to be connected to a grounding electrode as defined in 250.52 for a system supplied by the generator under the following conditions:
(1) The generator supplies only equipment mounted on the generator, cord-and-plug-connected equipment through receptacles mounted on the generator, or both, and
(2) The non?current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are bonded to the generator frame.

I think I am beginning to understand what you are trying to say. I think that you are saying that a portable generator can no longer be used due to the change in the definition of grounded.
I what I am saying is that 250.34 relieves the requirement that the system be connected to earth therefore there is no equipment grounding in use to be connected to earth.
In the use of a portable generator as a stand alone system there has never been anything grounded. The receptacles are not grounded nor the system itself.
With a portable generator the frame is not a conducting body that serves in place of the earth nor has it ever served as in place of earth.
All the receptacles on a portable generator are ungrounded circuits as they don?t nor are they required to be connected to earth.
If the portable generator is used to supply premises wiring of a building then earth connection is required.

 

[don_resqcapt19]

Mike,

If the portable generator is used to supply premises wiring of a building then earth connection is required.

Based on the definition of "premises wiring" a cord plugged into the receptacle on the generator is premises wiring.

In the use of a portable generator as a stand alone system there has never been anything grounded. The receptacles are not grounded nor the system itself.
With a portable generator the frame is not a conducting body that serves in place of the earth nor has it ever served as in place of earth.

I don't agree. The frame was used as the grounding electrode for portable generators that supplied cord and plug connected equipment.
Don

 

[jwelectric]

Based on the definition of "premises wiring" a cord plugged into the receptacle on the generator is premises wiring.

Wait, what was it that I said?

premises wiring of a building

That is what I thought I said. The key word in that statement was ?building?

I don't agree. The frame was used as the grounding electrode for portable generators that supplied cord and plug connected equipment.

Okay, Now I see why you are confused. The frame of a portable generator can not now nor could it ever have been a grounding electrode and it was never intended to be used as a grounding electrode.
The purpose of bonding to the frame is to establish a low impedance path to facilitate the overcurrent device.
A grounding electrode connects to earth. How can the frame of a portable generator connect anything to earth?
Unless a generator is connected to the premises wiring of a ?building? there is no requirement today or in the 2008 code cycle to connect a portable generator to earth. If the portable generator is connected to earth, then I can?t be portable can it?

 

[don_resqcapt19]

Mike,

That is what I thought I said. The key word in that statement was “building”

My copy of the NEC does not include the word "building" in the definition of "premises wiring".

Okay, Now I see why you are confused. The frame of a portable generator can not now nor could it ever have been a grounding electrode and it was never intended to be used as a grounding electrode.

Prior to the 2008 code the frame of the generator was the grounding electrode for the generator as under the 2005 code there was no requirement for a grounded system to be connected to earth.
This is one where we will have to agree to disagree.
Don

 

[jwelectric]

Mike, My copy of the NEC does not include the word "building" in the definition of "premises wiring".

I don’t believe that I said that the definition has the word building either. What I did say was that the premises wiring of a building would be grounded.

Prior to the 2008 code the frame of the generator was the grounding electrode for the generator as under the 2005 code there was no requirement for a grounded system to be connected to earth.

This is one where we will have to agree to disagree.

The word grounded means connected to earth. 250.34 does not require a portable generator to be connected to earth and relieves that requirement.

 

[don_resqcapt19]

Mike,

What I did say was that the premises wiring of a building would be grounded.

That doesn't have anything to do with the issue. I am talking about a portable generator that is supplying only cord and plug connected equipment and not a building or structure.

The word grounded means connected to earth. 250.34 does not require a portable generator to be connected to earth and relieves that requirement.

As I said before I do not agree with that statement. 250.20 requires the system supplied by the generator to be a grounded system. It is still a premises wiring system even if it only supplies cord and plug connected equipment based on the Article 100 definition. It is my opinion that the change in the definition of grounded over rules the statement in 250.34. In the 2008 code it is not possible to have a grounded system without a connection to earth. In the 2005 code it was not an issue because the frame of the generator was "some other conductive body that serves in place of the earth".
Note, I am not suggesting that this is any type of safety problem as I see no electrical or safety need a ground the generator system that only supplies cord and plug connected equipment, this is just a code wording issue.
Don

 

[tryinghard]

...It is my opinion that the change in the definition of grounded over rules the statement in 250.34. In the 2008 code it is not possible to have a grounded system without a connection to earth. In the 2005 code it was not an issue because the frame of the generator was "some other conductive body that serves in place of the earth".

Don,

I do think you have noticed an ambiguity but I'm stuck on the purpose for grounding a generator.

Are you saying 250-34 only complied when it was used as "some other conductive body that serves in place of the earth"? If so where are you directed to this thought specifically in 250-34?

250-34 is authored for very specific purposes and applications, it's wording has evolved to be even more descriptive about why it shall not be required to be connected to a grounding electrode meeting certain criteria. I agree with its application and I do not believe the definition or 250-20 changes 250-34.

The reasons and purposes for grounding a generator are still the same

 

[don_resqcapt19]

Trying,

I do think you have noticed an ambiguity but I'm stuck on the purpose for grounding a generator.

I understand the purpose and I don't see an electrical or safety reason to use a grounding electrode or even to bond the neutral on a portable generator, I just see a code reason to do so.

Are you saying 250-34 only complied when it was used as "some other conductive body that serves in place of the earth"? If so where are you directed to this thought specifically in 250-34?

Yes, that is exactly what I am saying.

I agree with its application and I do not believe the definition or 250-20 changes 250-34.

There is nothing in 250.34 that tells me that systems supplied by a portable generator do not have to comply with 250.20. If they don't then there needs to be an exception to 250.20. When you apply 250.20 and the new defintion of grounded, it makes, in my opinion, 250.34 void as far as the "no grounding electrode required" statement.
Don

 

[jwelectric]

From the 2008 Analysis of changes by the IAEI

 

[iwire]

I agree with Don and I think he has stated his case very concisely.

 

[don_resqcapt19]

Mike,
The picture you posted from the IAEI is a perfect example of a generator that supplies a system that is required by 250.20 to be a grounded system.
Don

 

[tryinghard]

There is nothing in 250.34 that tells me that systems supplied by a portable generator do not have to comply with 250.20. If they don't then there needs to be an exception to 250.20. When you apply 250.20 and the new defintion of grounded, it makes, in my opinion, 250.34 void as far as the "no grounding electrode required" statement.
Don

Don & Bob,

I believe 250-34(A) doesn't have an exception to 250-20 because 250-34(A) is an ungrounded system and 250-20 is only for grounded systems. My point in pressing this is to exemplify 250 as convoluted, even if some understand it well, the mixed use of terminology causes many very qualified electricians confusion.

"The frame of a portable generator shall not be required to be connected to a grounding electrode" is extremely explicit! At the same time it's truly ambiguous in the light of previous code!

 

[ryan_618]

Don, I agree with you. It looks like we need to try and address this via a 2011 proposal. I don't think it would meet the criteria for a TIA.