grounding electrodes and there connections

[rasmithircgov.com]

Re: grounding electrodes and there connections

So then as long as we meet the gounding electrode conductor sizing to the largest needed in the grounding system we have met the minimum to code. Boy this is a tough sell and I have aggreed with all of you. Now this person wants NEC interpetation. Just not pleasing some people.

 

[bennie]

Re: grounding electrodes and there connections

My opinions are apparently only my own. Observing my perception, is at the the discretion of the reader.

My approach to electrical science and theory is not always mainstream.

Good luck: Bennie

 

[rasmithircgov.com]

Re: grounding electrodes and there connections

To clear up my question from 4/3/03,
Lets say their is a 400 amp service on a residence, and the service is a back to back with 2 main disconnects. The electrician stubbed up a #1/0cu for his electrode conductor to the footer steel under the meter location. The code calls for a 400cu.serv. ent. cond.. Can the electrcian make the connection to the under ground water piping at a piont lets say 30' from his first point of his G.E.C. connection to a hose bib with 1/0cu. I hope this clears up the question, for this is how it was brought to me.
Thanks

 

[hornetd]

Re: grounding electrodes and there connections

Originally posted by rasmithircgov.com:
To clear up my question from 4/3/03,
Lets say their is a 400 amp service on a residence, and the service is a back to back with 2 main disconnects. The electrician stubbed up a #1/0 cu for his electrode conductor to the footer steel under the meter location. The code calls for a 400 cu serv. ent. cond.. Can the electrician make the connection to the under ground water piping at a point lets say 30' from his first point of his G.E.C. connection to a hose bib with 1/0 cu. I hope this clears up the question, for this is how it was brought to me.
Thanks

The 1/0 GEC that runs to the underground metal water piping must terminate to the piping within five feet of were it enters the building and must run unspliced to the main bonding jumper or to another electrode that is connected to the main bonding jumper with a GEC that is as large or larger.

So if the hose bib that you are talking about is within five pipe feet of were the underground metal water piping enters the building then it is an acceptable point at which to terminate the GEC. I would point out however that it would be better practice to make the connection on the street side of the first shut off valve in the underground metal water piping that is inside the building. That is because no plumber is going to cut or disconnect a pipe he/she cannot turn off. Since the outdoor valves are generally underground and under control of the water utility making the connection on the line side of the indoor valve reduces the likelihood of the GEC being disconnected at some time in the future.
--
Tom

 

[hornetd]

Re: grounding electrodes and there connections



[ April 12, 2003, 05:04 PM: Message edited by: hornetd ]

 

[rasmithircgov.com]

Re: grounding electrodes and there connections

Thanks for all your replies.

 

[lwciak]

Re: grounding electrodes and there connections

"Remember, the electrode is mainly for lightning protection, not for tripping breakers.
Karl "

Karl , I beg to differ, without the electrodes the breakers will never trip. This is precisely why we have the grounding bonding system, to facilitate the opening of the overcurrent device in the event of a fault current. And lightening is a whole new game. I would not trust a standard grounding system for lightening protection.

Thanks for letting me spend my 2 cents..

 

[russ]

Re: grounding electrodes and there connections

iwciak:
It is not the ground that trips an overcurrent device. Current will travel from an ungrounded phase on the grounded conductor back to the transformer, because of the bond between the (neutral) and equipment ground. A short circuit is between two parts of the transformer, not between a transformer and ground.
Maybe if we are lucky one of the guys will have a picture of this they can post.
Or aleast explain it better than I can.

Russ

 

[dereckbc]

Re: grounding electrodes and there connections

IWCIAK, Ground rods or any other form of electrodes have nothing to do with operating a breaker in your home or facility. In fact they are not needed at all. If an earth connection were required planes, trains, and automobiles wouldn,t be able to have electrical systems.

The electrode is just an earth reference point. It purpose is for lightning, static, and accidental contact with high voltage from outside sources, and personal safety to name a few.

 

[eprice]

Re: grounding electrodes and there connections

I agree with what russ said. Suppose our only grounding electrode were a driven rod or rods at the allowed maximum of 25 ohms to ground. If we had to depend on the current flowing through that grounding electrode to trip a breaker, the breaker would not trip. 120 volts will push 4.8 amperes through the 25 ohm resitance. Not enough to trip a 15 amp breaker. Fortunately, that is not the path for the fault current. It will travel along the EGC system, to the service disconnect where the EGC is bonded to the service neutral. From there the fault current travels along the service neutral back to the transformer completing the circuit with far less impedance and the breaker should trip, with or without the presence of a GEC and grounding electrode.

 

[Ed MacLaren]

Re: grounding electrodes and there connections

Perhaps this sketch of a typical Separately Derived System will help illustrate the "ground" fault clearing path.

The commonly used term "ground fault" often leads to confusion.

Ed

 

[bennie]

Re: grounding electrodes and there connections

Ed: Draw the delta/wye power distribution transformer, of the other system, supplying the premises transformer.

 

[Ed MacLaren]

Re: grounding electrodes and there connections

Bennie, I think this is what you had in mind.

Ed

 

[arneykaner]

Re: grounding electrodes and there connections

Here is my understanding of roots, why the old Codes required connection to the water pipe first:
making all water distribution pipes in the building at the same potential, to prevent "touch potential" shock, wich could be lethal in a bathroom, even if the difference of potential is small.

 

[arneykaner]

Re: grounding electrodes and there connections

In general, I agre with Tom Baker. However, in
all large buildings that I delt with, there is usually "main ground bar", so to speak in the main electrical room. This bar is connnected from
the ground bus of main service disconnect, or main
switchboard. And then, from that "main bar" grounding electrode conductors go to actual grounding points, such as driven electrodes, water main, building steel, etc.

 

[bennie]

Re: grounding electrodes and there connections

Ed: I will have to learn how to make drawings like you do. They are excellent.

I am referring to the transformer that will be supplying the one you show, as a separately derived system.

Regards: Bennie

[ April 24, 2003, 05:12 PM: Message edited by: bennie ]