grounding electrodes and there connections

[rasmithircgov.com]

In article 250-50-a of the 1999 nec. it states that when available the metal water pipng has to be used as an electrode, and supplimented. With other electrodes in the system, which do we goto first. Ive been taught to goto the metal water piping first and that all others are supplimental.Is this true or not. may I have references and/or code articles, if I naybe so bold.
Thank you

 

[iwire]

Re: grounding electrodes and there connections

2002 NEC 250.64 Grounding Electrode Installation

250.64(F) To electrodes:
A grounding electrode conductor shall be permitted to run to any convenient grounding electrode available in the grounding electrode system...... it goes on

250.50 describes what makes the grounding electrode system.

[ March 27, 2003, 06:19 PM: Message edited by: iwire ]

 

[rasmithircgov.com]

Re: grounding electrodes and there connections

has this changed since 1999?

 

[iwire]

Re: grounding electrodes and there connections

In the 1999 code all of this was in 250.50

 

[rasmithircgov.com]

Re: grounding electrodes and there connections

Looked up my own answer yes it has (f) was added

 

[rasmithircgov.com]

Re: grounding electrodes and there connections

Yes but couldn't find a order in which they had to be.I have been taught that other than metal water piping every other thing was a suppliment. now I have to try to convience others.

 

[karl riley]

Re: grounding electrodes and there connections

Since all electrodes have to be in before the power is turned on, why does it matter which you install first? And since new buildings these days usually have plastic water pipe supply, the word supplemental doesn't seem to have much meaning, unless you use more than required???
Remember, the electrode is mainly for lightning protection, not for tripping breakers.
Karl

 

[rasmithircgov.com]

Re: grounding electrodes and there connections

no the question was to which electrode do we have to attach to fist

 

[eprice]

Re: grounding electrodes and there connections

Originally posted by rasmithircgov.com:
no the question was to which electrode do we have to attach to fist

I don't think there is a requirement as to which one you go to first. 250.64(F) says "A groundng electrode conductor shall be permitted to be run to any convenient grounding electrode available in the grounding electrode system or to one or more grounding electrode(s) individually."

It goes on to say that "the grounding electrode conductor shall be sized for the largest grounding electrode conductor required among all the electrodes connected to it", so the order in which you connect to the elecrodes may affect the required size of the GEC(s).

By the way, this same language is found in the 2nd paragraph of 250-50 in the 1999 NEC.

 

[tom baker]

Re: grounding electrodes and there connections

the grounding electrode conductor goes to the first (most convinent) grounding electrode. the connection to other grounding electrodes are bonding jumpers. typically the grounding electrode that requires the largest GEC would be hit first, the rest can connect from it. Mike Holts 2002 Grounding and Bonding text has several great graphics to explain this.
Often in new construction the water pipe does not qualify as a grounding electrode.

 

[rasmithircgov.com]

Re: grounding electrodes and there connections

Yes I agree I have to try to convince other inspectors.I have heard said from others that if you have an attachment to footer steel lets say at a location under the meter, then 30' away come off that footer steel and hit metal water piping. Now the complaint from the inspector was how much current does that steel carry. My responce was it doesn't matter, the code says etc, etc. I am in total agreement with everyone here on the forum. Thanks for all your responses

 

[bennie]

Re: grounding electrodes and there connections

I agree with Tom, there should only be one ground electrode conductor terminating in a panel.

Unless the water piping is isolated from the dirt, it should be connected to the ground system not to the panel buss. Maybe theres 9 feet in the dirt

 

[bennie]

Re: grounding electrodes and there connections

I have seen transformers, in large buildings, with 150 feet of 1/0 run to the water pipe entrance from the X-O. Then 150 feet of #4 run to the service neutral/ground buss.

300 feet of ground loop. This is Mickey Mouse engineering.

 

[jxofaltrds]

Re: grounding electrodes and there connections

Here we bond from the panel neutral/ground bar to the cold water. ( I also bond the hot ).

Are you guys saying the it should go to the electrode instead?

 

[don_resqcapt19]

Re: grounding electrodes and there connections

Bennie,

I have seen transformers, in large buildings, with 150 feet of 1/0 run to the water pipe entrance from the X-O. Then 150 feet of #4 run to the service neutral/ground buss.

I don't understand how that makes a ground loop. That is two connections from the same point on the secondary side of the transformer to two different grounding electrodes. I don't see any difference in voltage to push current through this loop.
Don

 

[bennie]

Re: grounding electrodes and there connections

Mike Holt has a good article in the Aug 2002 edition of EC&M magazine, about objectionable current.

 

[bennie]

Re: grounding electrodes and there connections

Another good article is in the Feb. 2002 EC&M,
Power Quality Problems in Health Care Facilities.

Make note of the remarks about grounding the transformer.

 

[rasmithircgov.com]

Re: grounding electrodes and there connections

Bennie,
The code says you can goto each electrode individually.(250-50). So then would their not be more then one electrode conductor in the panel? It also says that it has to be brought to the same terminal bus or bar as the grounded service entrance conductor.(250-24-a) That stops at the first means of overcurrent protection correct? On slab inspections we would be able to tell if we have 10' or more water piping in the ground, and on the rough electric make sure the 5' of it entering the building(250-50)(250-50-a).

 

[bennie]

Re: grounding electrodes and there connections

True, You can feed electrodes individually, however the electrodes must be commonly bonded to become one.

Feeding from one point to numerous points is not bonding, it is multi point grounding.

 

[bennie]

Re: grounding electrodes and there connections

Every electrode will have a different impedance. This alone proves they are not bonded. Bonding is a short circuit, or low impedance circuit.