Neutral Conductors and Equipment Grounds tied together a

[bennie]

Re: Neutral Conductors and Equipment Grounds tied together a

I have four wires from my meter main to a panel across my garage. The ground conductor is a #4 al. The other three are 4/0. This is a cable assembly.

If this panel was connected with three wires, ground fault current would have a 4/0 conductor for a path. Now with the new interpretation of separating the NG at a panel there is only the #4 for fault clearing. This is backwards technology and is wrong. It is not what the code says.

As a wild hypothetical: Imagine a service panel with L-1 L-2, and N buses running the entire length of the house.

All branch circuits will connect to the closest location. There is no parallel current flow, yet the fault path is short, Everything that needs to be grounded will be grounded.

This is the same thing as having a remote panel.
So why the four wires? The code does not require four wires.

 

[curt swartz]

Re: Neutral Conductors and Equipment Grounds tied together a

Bennie,

You must have different code books than I do. The oldest NEC I have here is 1981 and while 250.152 has changed some over the years I still don't see that it would permit a bare neutral in a cable assembly to a sub panel. It does permit a bare neutral for the underground portion of a direct buried feeder.

 

[hurk27]

Re: Neutral Conductors and Equipment Grounds tied together a

So it was in "37" when it was introduce into the NEC to keep the grounds and neutral's separated.
I could remember doing this in "78" in Florida but wasn't sure if it was a local reg.

 

[curt swartz]

Re: Neutral Conductors and Equipment Grounds tied together a

From the 1981 NEC

250-60 allowed the bare conductor of type SE cable that originated from the service equipment to be used to ground the frames of ranges and dryers.

250-61 says the grounded conductor shall not be used for grounding non-current caring parts on the load side of the service disconnecting means. The 3 exceptions are for ranges and dryers as covered by 250-60, for separate buildings as permitted by 250-24 and for meter sockets.

 

[bennie]

Re: Neutral Conductors and Equipment Grounds tied together a

Karl: How much current has to flow in a single conductor to generate heat to a hazardous level?

I have never heard of magnetic fields creating any significant amount of heat except in the core of a transformer, and that is a combination of eddy currents and the load.

 

[iceman2610]

Re: Neutral Conductors and Equipment Grounds tied together a

bennie,
I understand what you are saying. You are correct in and installation where the subpanel has a main disconnect. If it is a main lug only panel, however, driving another groundrod and not floating the neutral, would cause a violation of code 250.24(A)(5).

Just pointing out that the code is written very generic to cover many different types of installations. The NEC is like the bible, a person can pick out any part and twist it to suit their application, but when you take into consideration all of the exceptions and alterations in the other chapters - however confusing it may seem at times - It is really quite complete. This statement is not to imply that the code is perfect by any means.

 

[curt swartz]

Re: Neutral Conductors and Equipment Grounds tied together a

iceman

What article in the NEC permits the neutral to be used for equipment grounding when connected to a panel that has a main disconnect but not in a panel that only has main lugs?

 

[shanz]

Re: Neutral Conductors and Equipment Grounds tied together a

So can we join them at a sub panel or not? I'm getting mixed readings or maybe I'm just not following. The way I read 250.24 (A)(5) we CAN'T.

Dennis

 

[iceman2610]

Re: Neutral Conductors and Equipment Grounds tied together a

Originally posted by curt swartz:
iceman

What article in the NEC permits the neutral to be used for equipment grounding when connected to a panel that has a main disconnect but not in a panel that only has main lugs?

Curt,
Article 250.32 allows for a three wire feeder to two or more buildings or structures supplied from a common service. However, if there is not a main breaker (Or means of disconnect) at this structure (a main lug only panel) then the ground would be on the load side of the service which would be in violation of Article 250.24(A)(5)

Sorry I am so slow to post, doing a lot of different stuff here.

 

[ryan_618]

Re: Neutral Conductors and Equipment Grounds tied together a

Originally posted by shanz:
So can we join them at a sub panel or not? Dennis

NO

 

[bennie]

Re: Neutral Conductors and Equipment Grounds tied together a

I want to retract my reference to 250.152 it does not apply.

 

[iceman2610]

Re: Neutral Conductors and Equipment Grounds tied together a

Originally posted by shanz:
So can we join them at a sub panel or not? I'm getting mixed readings or maybe I'm just not following. The way I read 250.24 (A)(5) we CAN'T.

Dennis

If the subpanel is within the same building or structure then the NEC requires a 4 wire feeder. In this case you would separate the neutrals and grounding conductors as it would be a true subpanel.

If it is in another building or structure fead from a common service, then you are permitted to run a 3 wire feeder and drive new ground rods (basically building a new service fed from the original). In the second case, there would be no need to separate the grounding conductors and neutrals as the second panel would need to be bonded as the primary.

If I am reading the code wrong, Feel free to correct me and show me my errors. Thanks.

 

[bennie]

Re: Neutral Conductors and Equipment Grounds tied together a

Iceman and the others are correct. My statements were regarding the neutral being connected to earth after the main.

I am only saying that with a cable assembly, there is no parallel path with 3 wires. There can be with four.

When there is a path for current, other than the neutral/ground, then one path has to be eliminated. This can be by floating the neutral or breaking the other path.

Check some of the older panels, how many have separate ground strips?

There is no code article about separating the neutral/ground from the equipment/ground conductors.

With only three current paths, on the feeder, the separation is not necessary.

Not many circuits in a dwelling had equipment ground wires until the 50s.

 

[don_resqcapt19]

Re: Neutral Conductors and Equipment Grounds tied together a

Bennie

There is no code article about separating the neutral/ground from the equipment/ground conductors.

Look at 250.142(B). This section very clearly prohibits the use of the grounded circuit conductor on the load side of the service disconnect for equipment grounding purposes.

250.142(B) Load-Side Equipment. Except as permitted in 250.30(A)(1) and 250.32(B), a grounded circuit conductor shall not be used for grounding non?current-carrying metal parts of equipment on the load side of the service disconnecting means or on the load side of a separately derived system disconnecting means or the overcurrent devices for a separately derived system not having a main disconnecting means.

Don

[ September 08, 2003, 02:47 PM: Message edited by: don_resqcapt19 ]

 

[karl riley]

Re: Neutral Conductors and Equipment Grounds tied together a

Shanz, I don't blame you for being confused by this thread. You ask a simple question, get a simple correct answer, and then a barrage of opinions about - what??.

Bennie, remember there is a vast silent majority who read these posts, apprentice electricians, inspectors, etc. We owe it to them to make clear when we are disagreeing with the electrical logic of the NEC, and when we are not in agreement with the meaning of the Code article quoted. Are you saying that 250-24(5)does not say what everyone else reads it as saying?

Karl

 

[bennie]

Re: Neutral Conductors and Equipment Grounds tied together a

I am not pointing out a technical descrepancy in the code. I am attempting to point out the wrong rules are applied for the separation of the neutral and ground conductors. The reason for the separation activity is to prevent parallel paths. If the parallel path can be prevented by other means, the other means is permitted.

250.24(5) Clearly states "grounding connection" The definition of grounding conductor is the ground electrode conductor.

There is no reference in 250.24 in prohibiting the interconnection of the neutral and the equipment ground conductors, which would be the case at a feeder supplied panel.

The equipment ground conductors, at a panel, are not connected to the earth at the panel location, so they are not "grounding conductors". Therefore a connection will not be a grounding connection.

The only code sections that apply to this issue are the ones concerning parallel path current.

The neutral/ground bus is electrically connected at many locations throughout the premises wiring system, This is the same as using the neutral/ground to complete the grounding circuit on the load side of the main. The only difference is the neutral/ground is for current carrying and the equipment/ground is not.

This is the reason there is no specific language indicating a floating neutral at every panel except the main.

Floating the neutral at panels increases the fault path for clearing purposes. The main reason for equipment grounding is compromised.

I am not trying to mislead anyone. As I have stated many times, my opinions are my own and it is up to the reader for accepting anything I write as fact or fantasy.

 

[Guest]

Re: Neutral Conductors and Equipment Grounds tied together a

Without offering any useful on-topic commentary I just want to interject that this is a very entertaining, helpful, and thought-provoking thread. It shouldn't be rocket science-- but it almost is. As a silent lurker on this thread I just wanted you to know that your comments (albeit somewhat contradictory) are read, processed, assimilated, and appreciated. I'm also hoping that somebody will have the last word that will pull it all together and provide the "right" answer that makes sense and keeps everybody safe. This is really important stuff.

../Wayne

[ September 08, 2003, 04:19 PM: Message edited by: awwt ]

 

[don_resqcapt19]

Re: Neutral Conductors and Equipment Grounds tied together a

Bennie,

There is no reference in 250.24 in prohibiting the interconnection of the neutral and the equipment ground conductors, which would be the case at a feeder supplied panel.

First, this is another problem with the use of the word "grounding" for conductors that have different purposes. In my opinion, 250.24(A)(5) prohibits the connection of EGCs to the grounded conductor anywhere on the load side of the serivce disconnect. Even if the word "grounding" in 250.24(A)(5) doesn't include EGCs, 250.142 is very clear that you cannot connect EGCs to the grounded conductor beyond the service disconnect enclosure.
Don

 

[bennie]

Re: Neutral Conductors and Equipment Grounds tied together a

Don: This is why I use; Equipment/ground, Earth/ground, and neutral/ground.

All wires that connect to the earth without supplying a load, are ground wires.

An adjective will identify their purpose.

 

[karl riley]

Re: Neutral Conductors and Equipment Grounds tied together a

Bennie, I think your reading of 250.24(A)(5) is incorrect and for me intellectually difficult to comprehend. If one has one's own definitions for electrical terms, then one has one's own edition of the NEC. The only trouble is, no one else will be using it.

I know that the meaning of words can be a point of disagreement. I learned this when I had a disagreement with a man who was the head of the State licensing bureau for electricians in a large northeastern state. He was telling me that it was a violation to let a plumber put an insulated coupling into a water pipe 10' outside the building. I quoted the NEC which said that 10' or more of water pipe qualified as a grounding electrode.

He replied, almost shouting over the phone, "It says 10' OR MORE, OR MORE!"

I had to send him a letter giving the definition of the word "or", and asking him to reply as to his definition of "or". He did not reply.

So when we don't agree on the meaning of simple words, agreement may not be possible.

Karl