new definition of grounded

[don_resqcapt19]

Does the new definition of grounded in the 2008 code cause any issues with the application of 250.34 in the cases where the system supplied by the portable generator is required to be a grounded system by the rules found in 250.20?
In the 2005 code the definition of grounded was as shown below. It is my opinion that the metal frame of the generator was a "conducting body that serves in place of the earth" and that permitted us to have a grounded system supplied from a portable generator with out the use of a grounding electrode that is in the earth.

Grounded. Connected to earth or to some conducting body that serves in place of the earth.

Now the 2008 code has the following definition of grounded.

Grounded (Grounding). Connected (connecting) to ground or to a conductive body that extends the ground connection. [ROP 5-9][ROP 5-12]

Does the change in the definition now require the use of a grounding electrode at a portable generator so that we can have a grounded system?
Don

 

[gndrod]

Does the new definition of grounded in the 2008 code cause any issues with the application of 250.34 in the cases where the system supplied by the portable generator is required to be a grounded system by the rules found in 250.20?
In the 2005 code the definition of grounded was as shown below. It is my opinion that the metal frame of the generator was a "conducting body that serves in place of the earth" and that permitted us to have a grounded system supplied from a portable generator with out the use of a grounding electrode that is in the earth.

Now the 2008 code has the following definition of grounded.

Does the change in the definition now require the use of a grounding electrode at a portable generator so that we can have a grounded system?
Don

Hi Don,

The key word "portable", IMO, directs the 'grounding' to a vehicular body that does not have a clear method of using an embedded electrode system to earth as the 2008 defines "ground". The metal frame is the 'floating' electrode until it is hooked up to a body that is fixed in place. I am not clear on the CMP's intent due to the new grounding definitions. Personally, I have a hard time with the present traditional electrical industry "ing" and "ed" usage for differentiation of an electrical ground plane that causes more confusion than it should.

The ground system definitions are basically attempting to define two separate intentions for protecting electrical configurations and does not address this clearly in the NFPA 70. I have worked in system integration where delineating the ground system differences between both vehicle and earth body interfaces differ due to "Source" characteristics. This is something I put in my 2005 proposal that didn't get any attention because of unclear "substantiation" or lack thereof. I am a little more informed now on how I would approach my next proposal for 2011. I better get off my soap box. Thanks for listening. rbj

 

[tryinghard]

Don, here's my take on this:

Does the new definition of grounded in the 2008 code cause any issues with the application of 250.34 in the cases where the system supplied by the portable generator is required to be a grounded system by the rules found in 250.20?

No, I think the '08' definition is just more descriptive and is not intended to change its application.

How we use the terminology "grounded system" matters though. I understand 250-20 to be for grounded systems and not ungrounded systems -- like a delta 3w supply -- in other words if you supply a 3ph 4w the XO must bond, to case and electrode, at the load side and everything downstream is considered to be a grounded system because of the XO bond and 250-20 applies. An ungrounded system does not have an XO conductor [grounded/neutral conductor] from the supply but is still grounded [bonded] the same throughout (250-4(B)), in this sense it can be said it is a grounded system but it's only grounded [bonded] NOT a "grounded system"!

...It is my opinion that the metal frame of the generator was a "conducting body that serves in place of the earth" and that permitted us to have a grounded system supplied from a portable generator with out the use of a grounding electrode that is in the earth.

This is the way I understand 250-34 (A) Portable Generators because it states "The frame of a portable generator shall not be required to be grounded and shall be permitted to serve as the grounding electrode". It still may require a grounding electrode if it meets the criteria of 250-50 but the electrode conductor would not bond to the neutral.

I think 250-34(B) Vehicle -Mounted generators do require an electrode because it's description does not say, "shall not be required to be grounded".

Does the change in the definition now require the use of a grounding electrode at a portable generator so that we can have a grounded system?

No; I hope I helped :-?

 

[don_resqcapt19]

It is my opinion that with the new definition, it is no longer possible to have a grounded system supplied by a generator without the use of a grounding electrode. I don't think this was the intent of the defintion change, but it is the result of the change. 250.20 requires some systems to be grounded systems. If you are supplying such a system from a portable generator, how can you do that without an grounding electrode?
Don

 

[tryinghard]

If the generator is not a SDS the equipment bonding routes to the existing electrode at the source so there is no need for another. If a generator is not a SDS but still requires an electrode the neutral cannot bond to the electrode/frame but the electrode conductor does, this would be like a separate structure.

The language in 250-34(A) exempts this particular arrangement of a portable generator from a rod but allows the frame to be an electrode (like a building frame) while obtaining the use of the existing electrode system through the bonding route.

Sometimes pictures help:

 

[don_resqcapt19]

Trying,

If the generator is not a SDS

I am talking about a portable stand alone generator...unless you wire it to supply a building it will always be SDS.

The language in 250-34(A) exempts this particular arrangement of a portable generator from a rod but allows the frame to be an electrode (like a building frame) while obtaining the use of the existing electrode system through the bonding route.

That is the problem...the frame is no longer permitted to be the grounding electrode as a result of the defintion change. The words that were removed, "or to some conducting body that serves in place of the earth", from the defintion of grounded were what permitted the frame of a portable generator to be used as a grounding electrode. The language in 250 that says a ground rod is not required does not change this. The problem is that the rule in 250.20 requires many systems to be grounded systems. The new defintion of grounded does not permit the generator frame to be the grounding electrode. With the new rule the code does not permit a portable generator to supply any system that is required to be a grounded system unless you provide a grounding electrode.
Don

 

[tryinghard]

Check out the language in 250-34(A) 2008, what do ya think?

 

[tryinghard]

Don, with all due respect I think your misapplying 250-20. For additional props please notice the "Author's Comment" in the attached "Grounding verses Bonding newsletter for this section.

He states:
"Author?s Comment: System grounding, the intentional bonding of the electrical supply source to the metal case, provides the low-impedance fault-current path necessary to clear a ground fault. Figure 250?43"

250-20 is not meant to direct us to install grounding electrodes as in 250-52, it is specifically directing us to bond the neutral to case to enable fault current path to source XO from all non-current carrying conductive parts. 250-20 is also specifically for premises wiring systems.

Portable generators are a source and can be separately derived but are specifically addressed in 250-34

 

[gndrod]

Pics

Pics

I like those illustrations. Would there be more that support what Don is referring to...I.e. Portable gen bonding to an electrode? rbj

 

[don_resqcapt19]

Trying,

Don, with all due respect I think your misapplying 250-20.

How is that?

250.20(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: ...

The only way you can have a grounded system is to ground it. Under the new definition of "grounded" in the 2008 code you have to have a grounding electrode. Under the 2005 definition you could use "some conducting body that serves in place of the earth'. In the case of portable generators that was the frame. That is not permitted under the 2008 code.

I am well aware of what 250.34(A) says and that does not change my opinion. The change in the defintion of grounded overrides the wording in 250.34 as it is no longer possible to have a grounded system by using the frame of the generator as "a conducting body that serves in place of the earth

With all due respect to Mike's comments, I don't agree. 250.20 is requiring a grounding electrode as that is the only way to have a grounded system. The fault clearing has to do with bonding and not with grounding.
Don

 

[tryinghard]

Trying,
How is that?
The only way you can have a grounded system is to ground it.

Don,

Article 250 really is convoluted with its wording and it causes us all grief! 250-20 is for 'systems to be grounded' meaning grounded systems as opposed to ungrounded systems, it's not written for the requirements of electrodes or their installation. The problem is it's using wording that has multiple meanings.

250-20 is qualifying which circuits we must bring the 'XO' (grounded/neutral) conductor with its phases. Opposite this, as example, a delta 3ph 3w is considered an ungrounded system only because the 'XO' (grounded/neutral) conductor does not come with it from the secondary transformer or supply, it intentionally allows a ground fault to remain on conductive items giving time to troubleshoot critical machinery, a second fault will actually be a phase to phase short operating OCPD's. In this light when you don't have an ungrounded system you must have a grounded system that includes the XO conductor from source supply with the phases.

250-20 is not referencing a grounding system as described in 250-50 rather it is referencing the type of system denoted by its supply or no supply of a grounded conductor (neutral) :roll:

 

[tryinghard]

An ungrounded system is required to be grounded as per 250-4(B), 24(E), 30(B), & 32(C) to list a few.

 

[don_resqcapt19]

Trying,

Article 250 really is convoluted with its wording and it causes us all grief! 250-20 is for 'systems to be grounded' meaning grounded systems as opposed to ungrounded systems, it's not written for the requirements of electrodes or their installation.

250 doesn't cause me any grief...I fully understand what it says, but the code making panels did not look close enough at this change. I stand by by statement that you cannot have a grounded system without a grounding electrode. There is absolutely nothing in the NEC that says otherwise.

An ungrounded system is required to be grounded as per 250-4(B), 24(E), 30(B), & 32(C) to list a few.

An ungrounded system is not required to be grounded. It is required to have a grounding electrode system and equipment grounding conductors, but they are not required to be grounded. A grounded system has a circuit conductor that is grounded, an ungrounded system does not.

250-20 is qualifying which circuits we must bring the 'XO' (grounded/neutral) conductor with its phases.

No it is not. There is no requirement, other than for a service, to extend the grounded conductor beyond the system bonding jumper. The rule in 250 tells us when we must create a grounded conductor.
Don

 

[jim dungar]

I stand by by statement that you cannot have a grounded system without a grounding electrode. There is absolutely nothing in the NEC that says otherwise.

So, we cannot have grounded systems in ships, airplanes, or the antarctic?

 

[don_resqcapt19]

Jim,

So, we cannot have grounded systems in ships, airplanes, or the antarctic?

Not with the change in the wording of the definition (note this only applies to NEC applications, sure you can have what is called or know as a grounded system with out a connection to earth in non-NEC applications). Under the previous code you could use "some conductive body that serves in place of the earth", with those words removed from the definition, you can't have a grounded system without a connection to earth.
My whole point in this thread is that the change in the definition of grounded has caused some problems that were not anticipated by the CMP.
Don

 

[tryinghard]

Don,

An ungrounded system is not required to be grounded.

How can you explain 250-30(B) "The equipment of an ungrounded separately derived system shall be grounded"?

It is required to have a grounding electrode system and equipment grounding conductors, but they are not required to be grounded.

Is this possible in premises wiring? Example: 250-4(B), 24(E), 30(B), & 32(C) are not grounded?

No it is not. There is no requirement, other than for a service, to extend the grounded conductor beyond the system bonding jumper. The rule in 250 tells us when we must create a grounded conductor.

This statement seems to be contradicting; can we create a grounded conductor from something other than the XO of the source?
Are you actually talking about the Grounding Electrode Conductor 250-24(C), 62, 64, 66, 68, & 70? This is certainly not the same conductor as the Grounded Conductor 250-142, 250-24(C), & 32(B)(2)
What determines the secondary circuit of a transformer?

250 doesn't cause me any grief...I fully understand what it says, but the code making panels did not look close enough at this change. I stand by by statement that you cannot have a grounded system without a grounding electrode. There is absolutely nothing in the NEC that says otherwise.

For premises wiring I fully agree it's exactly as you say below:

A grounded system has a circuit conductor that is grounded, an ungrounded system does not.

 

[don_resqcapt19]

Trying,

How can you explain 250-30(B) "The equipment of an ungrounded separately derived system shall be grounded"?

A grounded system, (what I am talking about in this thread) has a grounded circuit conductor (commonly know as a neutral), that is not the same thing as requiring the equipment of an ungrounded system to be grounded. The only thing that is the same is the fact that in both cases the rules require something to be grounded (connected to the earth). In the case of a system that is required to be grounded, the rules require that both a circuit conductor and the exposed conductive parts be grounded. In the case of an ungrounded system, only the exposed metal parts are grounded.

Quote:
Originally Posted by don_resqcapt19
No it is not. There is no requirement, other than for a service, to extend the grounded conductor beyond the system bonding jumper. The rule in 250 tells us when we must create a grounded conductor.

This statement seems to be contradicting; can we create a grounded conductor from something other than the XO of the source?

In some cases we can, however that has nothing to do with my statement. If you have a 480Y/277 volt system and you are supplying a lighting panel and an MCC from this system, there is no code or electrical reason to bring the grounded conductor to the MCC.

For premises wiring I fully agree it's exactly as you say below:
Quote:
Originally Posted by don_resqcapt19
A grounded system has a circuit conductor that is grounded, an ungrounded system does not.

Ok, so how do we get a grounded system for cord and plug connected equipment from a protable generator under the 2008 code without a grounding electrode? Please review the Article 100 definition of premises wiring before responding.

Are you actually talking about the Grounding Electrode Conductor 250-24(C), 62, 64, 66, 68, & 70? This is certainly not the same conductor as the Grounded Conductor 250-142, 250-24(C), & 32(B)(2)

Not exactly, but you can't have a grounded system without a grounding electrode conductor.

What determines the secondary circuit of a transformer?

I don't know what you are asking here.
Don

 

[jim dungar]

My whole point in this thread is that the change ... has caused some problems that were not anticipated by the CMP.

Wow, is that a surprise. I am sure it has never happened before.

 

[tryinghard]

Don,

In some cases we can, however that has nothing to do with my statement. If you have a 480Y/277 volt system and you are supplying a lighting panel and an MCC from this system, there is no code or electrical reason to bring the grounded conductor to the MCC.

With code this would be a violation of 250-20(B)(2), you would need to be 480v delta 3w ungrounded for the MCC and you cannot feed a 277v system as ungrounded so one of these needs to pass through a SDS to enable it.

Electrically you cannot mix modes from one source, unless you go through another source, if it is a grounded system the reason for ungrounded wont function and in reverse if it is an ungrounded system the OCPD wont function because there is no source connection. This is the reason for 250-20

Ok, so how do we get a grounded system for cord and plug connected equipment from a protable generator under the 2008 code without a grounding electrode?

With 250-34(A) "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", it's simply not required.

Please review the Article 100 definition of premises wiring before responding.

I did and I feel like I understand what it is but I do not understand your reason for referring to it?

 

[crossman]

Don,


With code this would be a violation of 250-20(B)(2), you would need to be 480v delta 3w ungrounded for the MCC and you cannot feed a 277v system as ungrounded so one of these needs to pass through a SDS to enable it.

I disagree.

Example:

480/277 3-phase 4-wire* service brought to service equipment. From the service equipment, we have a feeder to a 480 volt 3-phase MCC and another feeder to a Lighting Panel that needs 480/277 3-phase 4-wire. The Lighting Panel feeder needs three phases (hot, ungrounded) and the neutral (grounded conductor) but the MCC only needs three phase (hot, ungrounded) conductors. Obvioulsy both the Panel and the MCC will still require Equipment Grounding Conductors.

The MCC which is downstream of the service does not require a grounded conductor if it is not needed by the loads.



* Or whatever the IEEE or whoever's current name for the system is, but who the heck made them god?