Article 100 Definition Addition! SHORT CIRCUIT

[Pierre C Belarge]

There are times a short circuit may "burn clear" without the OCPD actually opening.

 

[ibew441dc]

Short Circuit: A fault between two conductors that cause a properly sized OCPD to open, which does not include the Equipment Grounding Conductor of a circuit.

It sounds similar to the way I see it.:smile:.......

Short Circuit-An intentional or unintentional, low impedance conducting connection, between any ungrounded conductor(s) establishing a difference of potential, or between any ungrounded conductor(s) and a grounded conductor.

FPN (1): A Short circuit is not a Ground Fault (see Article 250.2 Definitions)
FPN (2): A Short Circuit is not an intentional or unintentional electrical conducting connection between a grounded conductor and an equipment grounding conductor.(see 250.6 Objectional Current)

 

[joebell]

The connection of an unintended Grounded Conductor to an EGC is Objectional Current. (see 250.6) Not a Short Circuit and not a Ground Fault.

I thought a connection between a grounded conductor and an EGC was a ground fault condition and the result of this connection was objectional current flow.




I do agree that there should be a clear definition for shrt circuit in Art. 100. I understand where you are comming from, take the term receptacle and outlet they are used interchangablly all the time in our industry.




Joe

 

[ibew441dc]

250.6

250.6

I thought a connection between a grounded conductor and an EGC was a ground fault condition and the result of this connection was objectional current flow.

I do agree that there should be a clear definition for shrt circuit in Art. 100. I understand where you are comming from, take the term receptacle and outlet they are used interchangablly all the time in our industry.

Joe

Take a close look at 250.6 in the NEC

 

[iwire]

Every wonder what the definition of a SHORT CIRCUIT was in the NEC?(I sure do)

Article 100-Part I and II should include an authoritative definition of the commonly used (and easily mis-used term).

Okay.....to avoid this part........I know, I know....see 90.1(C).blah, blah , blah...a trained person should know what a short circuit is.True, but based on what reference?, I challenge you to google it, check different dictionary's, IEEE, maybe NEMA even? My point is .....the different sources imply different things.

......A trained person should respect the fact that we all have to be accountable to an authority.........in the 'Electrical Installation World', that authority is NFPA 70(NEC).

The NEC states pretty clearly what an Overcurrent is and subdivides it into 3 categories.:smileand this is only one example)


Overload is in Article 100, Ground Fault is in 250,..... so where is SHORT CIRCUIT?

Do we need to define it?

Is the term 'short circuit' currently being used in the NEC and causing people confusion or misinterpretation of the NEC?

I think the NFPA has us use Merriam Webster for common definitions.


Merriam Websters definition of short circuit;

1 : to apply a short circuit to or establish a short circuit in
2 : bypass
3 : frustrate , impede

 

[joebell]

I have looked at it several times and the only thing I keep asking myself is what type of condition causes objectionable current to flow? This must be defined as well IMHO. 250.6(C) states "temporary currents such as ground faults, shall not be classified as objectionable current" I believe this is due to the OCPD tripping on a fault between an ungrounded conductor and the EGC. What do you call a condition where the grounded conductor accidentaly comes in contact with the EGC. IMO the result is objectionable current but what is the condition called?

Short Circuit = ungrounded to ungrounded = fault current
Ground Fault = ungrounded to EGC = fault current
? = grounded to EGC = objectionable current



Joe

 

[ibew441dc]

Sc=h2h & h2n, gf=h2egc, oc=n2egc

Sc=h2h & h2n, gf=h2egc, oc=n2egc

Short Circuit = ungrounded to ungrounded = fault current
Ground Fault = ungrounded to EGC = fault current
? = grounded to EGC = objectionable current

Joe

the first one is close....
Short Circuit= ungrounded to ungrounded, and ungrounded to grounded(neutral)=Fault Current

Ground Fault=ungrounded to EGC=Fault Currrent.....Bingo!:smile:

Objectional Current = grounded to EGC=Objectionable Current......correct-a-mundo:smile:

Assuming a systems neutral conductor is properly bonded at the service to the EGC,via the MBJ, the voltage potential is zero (between the two). From that single point all the way to the final load, the neutral and EGC must be kept independent of each other(the voltage between the 2 is still zero).A neutral to EGC bond that establishes parallel path for neutral current will not create an explosion like a fault (short circuit or a ground fault)because there is no difference of potential. But what does happen is you have neutral current flowing on metal parts not intended to perform that function, Objectionable Current, not fault current.

A neutral to case bond at other than the Service, and a neutral to case bond at other than the source of a separately derived system are examples of establishing objectionable current.

 

[joebell]

the first one is close....
Short Circuit= ungrounded to ungrounded, and ungrounded to grounded(neutral)=Fault Current

Ground Fault=ungrounded to EGC=Fault Currrent.....Bingo!:smile:

Objectional Current = grounded to EGC=Objectionable Current......correct-a-mundo:smile:

Assuming a systems neutral conductor is properly bonded at the service to the EGC,via the MBJ, the voltage potential is zero (between the two). From that single point all the way to the final load, the neutral and EGC must be kept independent of each other(the voltage between the 2 is still zero).A neutral to EGC bond that establishes parallel path for neutral current will not create an explosion like a fault (short circuit or a ground fault)because there is no difference of potential. But what does happen is you have neutral current flowing on metal parts not intended to perform that function, Objectionable Current, not fault current.

A neutral to case bond at other than the Service, and a neutral to case bond at other than the source of a separately derived system are examples of establishing objectionable current.

I understand what you are saying , I'm just having a difficult time with the terms. It seems redundant to me to label the condition and the result with same term. The result of a ground fault or a short circuit condition is fault current but the result of objectionable current is objectionable current.




Joe

 

[ibew441dc]

I understand what you are saying , I'm just having a difficult time with the terms. It seems redundant to me to label the condition and the result with same term. The result of a ground fault or a short circuit condition is fault current but the result of objectionable current is objectionable current.
Joe

How about this....:smile:

Current flowing on normally non current carrying conductors and/or the earth = Neutral to EGC(at other than the service and the source of a separately derived system = Objectional Current

 

[ibew441dc]

Vote YES-On The New Definition(doesn't have to be mine exactly)

Vote YES-On The New Definition(doesn't have to be mine exactly)

Do we need to define it?

Is the term 'short circuit' currently being used in the NEC and causing people confusion or misinterpretation of the NEC?

Yes, I do think a definition would be a valuable addition to the NEC.

I think the lack of this definition does create confusion or misinterpretation of the NEC.
A similar example of 'definition evolution' is pretty much everything associated with Grounding and Bonding.Don't you agree that prior to the recent changes,especially in the 08 NEC, the lack of proper definitions created confusion or misinterpretation.

Now before you say....that's a different issue all together, consider the fact that Short Circuit is commonly misused to describe a ground fault or objectionable current.

 

[Pierre C Belarge]

Yes, I do think a definition would be a valuable addition to the NEC.

I think the lack of this definition does create confusion or misinterpretation of the NEC.
A similar example of 'definition evolution' is pretty much everything associated with Grounding and Bonding.Don't you agree that prior to the recent changes,especially in the 08 NEC, the lack of proper definitions created confusion or misinterpretation.

Now before you say....that's a different issue all together, consider the fact that Short Circuit is commonly misused to describe a ground fault or objectionable current.

Ground fault and objectional current are covered in the NEC and much documetation.

Adding a definition is not going to stop the confusion. People reading and studying is going to help.

 

[George Stolz]

Yes, I do think a definition would be a valuable addition to the NEC.

I think the lack of this definition does create confusion or misinterpretation of the NEC.

Humoring your idea for a moment (which I still disagree with), is there a safety concern here?

A similar example of 'definition evolution' is pretty much everything associated with Grounding and Bonding.Don't you agree that prior to the recent changes,especially in the 08 NEC, the lack of proper definitions created confusion or misinterpretation.

Absolutely, and there was a genuine safety impediment with the confusion of the terms. There's no requirement to create a short circuit (okay, maybe one I can recall). There are multiple requirements to create "grounds".

Not knowing what they're talking about when creating a grounding system can result in a fatality. Is there a similar problem with the term "short circuit"?

I press this because you are going to be pressed by the CMP for a very good answer to that question. I can already hear the statement "the existing language has been used successfully for many years. Insufficient substantiation to add a definition."

 

[quogueelectric]

Assuming a systems neutral conductor is properly bonded at the service to the EGC,via the MBJ, the voltage potential is zero (between the two). From that single point all the way to the final load, the neutral and EGC must be kept independent of each other(the voltage between the 2 is still zero)..

This statement is not correct assuming that any current is on the circuit and it is properly bonded at only one point.

The resistance of the wire is in series with the load and causes a proportional voltage drop on both sides of the load which is determined by the resistance of the wire and the voltage of the source.
Assuming the wire length and mechanically connected parts are eaqually conductive. There is a potential difference always between a conducting cable and a non conducting cable of the same length/resistance.
This of course gets more complicated when we are talking 3 phase loads.
When the conducting grounded cable comes into contact with ground at the load the resitance of the 2 cables is halved ( This model also ignores all current actually carried by dirt-earth) and the total circuit current rises slightly yet the current is split on the 2 wires back to the source to the point of service bonding.

This is a fairly complex mathematical process which is oversimplified for most teaching purposes. This must also include capacitive and inductive coupling along the route and the changes in reactance and suseptance when a neutral is grounded to the ground wire at the load.
If you dont believe this touch the neutral to ground at a load and then explain why the gfci tripped.
I totally agree that this definition is horrible and the Nfpa really dropped the ball with all of these engineers running around there and no one picked up on this. To define a ground fault as only on ungrounded conductors is simply dangerous and wrong in my opinion.

Heck what do I know I am just a dumb electrician???

 

[ibew441dc]

Ground fault and objectional current are covered in the NEC and much documetation.

Adding a definition is not going to stop the confusion. People reading and studying is going to help.

Adding a definition is not going to stop the confusion???:-?I don't even know how to respond to that. A definition would IMO be an attempt.

People reading and studying is going to help, although those who do so will be held accountable for the things we say and do. Clearly defining terms in an appropriate manner is extremely important.

 

[quogueelectric]

Adding a definition is not going to stop the confusion???:-?I don't even know how to respond to that. A definition would IMO be an attempt.

People reading and studying is going to help, although those who do so will be held accountable for the things we say and do. Clearly defining terms in an appropriate manner is extremely important.

This is a very confusing part of the code partly because some of the teachers who teach us basic ohms law simplify it without calculus so that the average joe shmoe can grasp it quickly enough for basic electrical work.
As you get more into the calculus it opens up a whole can of worms with many different things going on simultaneously and not to be ignored.
For example when you study a lightbulb being powered the current on the copper is studied and the current on the air we breath and the current on the wire insulation is ignored because thier values are so low that they can be thrown out.
Enter an arc flash where the air becomes Ionized and we have a whole different animal. Draw that using ohms law acurately you will be busy for a while.
ALL paths must be counted in the equation for the engineers version. Simplified one line diagrams for the rest of us

 

[ibew441dc]

Humoring your idea for a moment (which I still disagree with), is there a safety concern here?

Your telling me that defining a short circuit is not a safety concern??
Just the words used together, period, is a red flag that there is a problem.

Absolutely, and there was a genuine safety impediment with the confusion of the terms. There's no requirement to create a short circuit (okay, maybe one I can recall). There are multiple requirements to create "grounds".

Lets not get off track as to my intent. I have not stated or implied the creation of a short circuit as a requirement, nor have I said anything about creating grounds.I did, however, say that a Short Circuit and a Ground Fault are different.

Not knowing what they're talking about when creating a grounding system can result in a fatality. Is there a similar problem with the term "short circuit"?

Absolutely, Fault levels are significantly higher from a short circuit then a ground fault,due to a higher voltage across the line (line to line).

90.8(B) Number of Circuits in Enclosures. It is elsewhere provided in this Code that the number of wires and circuits confined in a single enclosure be varyingly restricted. Limiting the number of circuits in a single enclosure minimizes the effects from a short circuit or ground fault in one circuit.

Hmmmm????the effects of short circuits or ground faults must be dangerous.....Article 250 defines a ground fault......so I clearly know what to avoid there. But what is a short circuit.....it sounds dangerous too(as a matter of fact more dangerous)

90.1 Purpose.
(A) Practical Safeguarding. The purpose of this Code is the practical safeguarding of persons and property from hazards arising from the use of electricity.

A short circuit is a hazard arising from the use of electricity.

(C) Intention. This Code is not intended as a design specification or an instruction manual for untrained persons.

A definition of Short Circuit would clear up any debate as to its meaning to trained persons, thus resulting in safer installations.

110.9 Interrupting Rating.
Equipment intended to interrupt current at fault levels shall have an interrupting rating sufficient for the nominal circuit voltage and the current that is available at the line terminals of the equipment. Hmmmm?? Ground Fault, Objectionable Current, or Short Circuit.Using process of elimination(based on code facts) it must be a short circuit.

These are a few examples, of why I think a clear definition would be appropriate.

I press this because you are going to be pressed by the CMP for a very good answer to that question. I can already hear the statement "the existing language has been used successfully for many years. Insufficient substantiation to add a definition."

That may be true but from the sounds of it, there's a couple of years until the next shot. Thats plenty of time to tune up a case.

 

[ibew441dc]

This statement is not correct assuming that any current is on the circuit and it is properly bonded at only one point.

The resistance of the wire is in series with the load and causes a proportional voltage drop on both sides of the load which is determined by the resistance of the wire and the voltage of the source.
Assuming the wire length and mechanically connected parts are eaqually conductive. There is a potential difference always between a conducting cable and a non conducting cable of the same length/resistance.
This of course gets more complicated when we are talking 3 phase loads.
When the conducting grounded cable comes into contact with ground at the load the resitance of the 2 cables is halved ( This model also ignores all current actually carried by dirt-earth) and the total circuit current rises slightly yet the current is split on the 2 wires back to the source to the point of service bonding.

This is a fairly complex mathematical process which is oversimplified for most teaching purposes. This must also include capacitive and inductive coupling along the route and the changes in reactance and suseptance when a neutral is grounded to the ground wire at the load.
If you dont believe this touch the neutral to ground at a load and then explain why the gfci tripped.

I agree. In the attempt to make a point I made a false statement, stating that the voltage potential would be the same at both points. My point was to illustrate the fact that a neutral to EGC typically will not result in an explosion, like a ground fault or a short circuit, and the the result is objectionable current, not a short circuit or ground fault.

I totally agree that this definition is horrible and the Nfpa really dropped the ball with all of these engineers running around there and no one picked up on this. To define a ground fault as only on ungrounded conductors is simply dangerous and wrong in my opinion.

Heck what do I know I am just a dumb electrician???

Heck what do I know I am just a dumber electrician:grin:???

 

[ibew441dc]

How would you define.......

How would you define.......

This is a very confusing part of the code partly because some of the teachers who teach us basic ohms law simplify it without calculus so that the average joe shmoe can grasp it quickly enough for basic electrical work.

Most of us(my self included).......at least the electricians I have met and worked with are average joe shmoes:smile:. Us Joe shmoes are the qualified persons....or are we????

As you get more into the calculus it opens up a whole can of worms with many different things going on simultaneously and not to be ignored.
For example when you study a lightbulb being powered the current on the copper is studied and the current on the air we breath and the current on the wire insulation is ignored because thier values are so low that they can be thrown out.
Enter an arc flash where the air becomes Ionized and we have a whole different animal. Draw that using ohms law acurately you will be busy for a while.
ALL paths must be counted in the equation for the engineers version. Simplified one line diagrams for the rest of us

So you seem pretty in tune:smile:....
How would you define a short circuit? How would you define a Ground Fault? How would you define Objectionable Current? Base your answers on the National Electrical Code, please:smile:

 

[iwire]

Yes, I do think a definition would be a valuable addition to the NEC.

I think the lack of this definition does create confusion or misinterpretation of the NEC.
A similar example of 'definition evolution' is pretty much everything associated with Grounding and Bonding.Don't you agree that prior to the recent changes,especially in the 08 NEC, the lack of proper definitions created confusion or misinterpretation.

Now before you say....that's a different issue all together, consider the fact that Short Circuit is commonly misused to describe a ground fault or objectionable current.

Give us an example of where the NEC uses the term short circuit that leads to confusion.

 

[ibew441dc]

Give us an example of where the NEC uses the term short circuit that leads to confusion.

Obviously:roll::smile:, My opinion is now biased in this regard, and so is yours. How do we come to a conclusion if both are convinced that either (a) the definition would provide clarity and be beneficial ,or (b) the definition is unnecessary and would be of no benefit

Many electricians(the qualified persons) loosely refer to a ground fault as a short circuit, basing there point of view on references outside of the NEC. Others would argue that a ground fault is not a short circuit, basing there point of view on the NEC. Both sides IMO have enough substantial evidence to make a case on either side, resulting in confusion.

Enter Objectionable Current and you open up a related debate...What is objectionable current? Is it the result of an illegal neutral to EGC connection?, is it a short circuit?, it's definitely not a temporary ground fault, is an Arc Fault Objectionable Current?, [is an Arc Fault a short Circuit(I don't think it is)].

90.8(B) Number of Circuits in Enclosures. It is elsewhere provided in this Code that the number of wires and circuits confined in a single enclosure be varyingly restricted. Limiting the number of circuits in a single enclosure minimizes the effects from a short circuit or ground fault in one circuit.

NECPLUS-Staff Note for 90.8(B)
The limitations noted in 90.8(B) on number of wires and circuits in a single enclosure also minimize the heating effects inherently present whenever current-carrying conductors are grouped together.

Some argue that the definition that is in McGraw-Hill Dictionary of Scientific and Technical Terms is good enough to make a clear distinction between and/or no distinction the terms. Some say a ground fault is a type of short circuit , but also say, a short circuit is not a ground fault:-?

There are a number of times that the phrase's, short circuit or ground fault , short circuit and ground fault, short circuit,and, ground fault, are used through the NEC. When used in this manner the NEC is clearly stating the two are different.