multiple ground clamps at grounding electrode

[stamcon]

Re: multiple ground clamps at grounding electrode

Bennie, if code wanted only one GEC leaving the panel, shouldn't the wording be "The grounding electrode conductor..."?

 

[bennie]

Re: multiple ground clamps at grounding electrode

There is not a big deal how many conductors leave the panel. Actually there is no real problem with none, on a residential dwelling.

If I lived in a high lightning area, I would want one conductor to earth close to the service panel. The other electrodes would then be bonded outside or under the house.

I want to direct a lightning surge to the exterior, not across ceiling joists to the water pipe.

 

[websparky]

Re: multiple ground clamps at grounding electrode

Now ya see, you went and threw lightning into the mix!

This is a whole separate issue. Here is a link to a well know and respected authority on the subject of lightning.
http://www.lightningsafety.com/

After you spend a few hours reading through the data available, maybe you will come back with a new enlightened opinion?

Give it a try!

[ March 22, 2004, 08:34 PM: Message edited by: websparky ]

 

[dirtrider]

Re: multiple ground clamps at grounding electrode

I appreciate everything everyone has to say but my question hasn't been answered. I have always run a 4 to the ufer and continued on to the water without cutting the wire. I would then run a seperate 6 to the gas from the service panels neutral buss. I was taught this is how it is done and never questioned it. I don't think connecting multiple ground clamps to the ufer or ground rod is right but can't find that spelled out. As for you guys saying the water is a supplimental grounding electrode it cannot be used to suppliment a ground rod of over 25 ohms.

 

[bennie]

Re: multiple ground clamps at grounding electrode

I am not addressing lightning strikes. I am referring to lightning created transient surges in a secondary to a premises wiring system.

A surge is when there is a strike on the primary lines that increase the voltage. The strike may be miles away. This increase appears on the secondary through capacitance coupling in the transformer, not inductive coupling through the windings.

This surge will return to the point of it's creation, which is the primary line, not the local transformer.

 

[websparky]

Re: multiple ground clamps at grounding electrode

Nineteen minutes!

 

[stamcon]

Re: multiple ground clamps at grounding electrode

Dirtrider, if a metallic water pipe with at least 10' in contact with earth is on the premises, it shall be used as an electrode and shall be supplemented.

250-50(a)(2) 99NEC spells out the bonding of a supplemental electrode.

 

[iwire]

Re: multiple ground clamps at grounding electrode

Originally posted by dirtrider:
I have always run a 4 to the ufer and continued on to the water without cutting the wire. I would then run a seperate 6 to the gas from the service panels neutral buss.

That is OK, personally I would not run the 6 AWG to the gas pipe, but it could be a local expectation of inspectors.

A gas pipe is not to be used as a grounding electrode.

250.52(B) Electrodes Not Permitted for Grounding. The following shall not be used as grounding electrodes:
(1) Metal underground gas piping system
(2) Aluminum electrodes

The gas line needs to be bonded, look at the part I made bold.

250.104(B) Other Metal Piping. Where installed in or attached to a building or structure, metal piping system(s), including gas piping, that may become energized shall be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor where of sufficient size, or to the one or more grounding electrodes used. The bonding jumper(s) shall be sized in accordance with 250.122 using the rating of the circuit that may energize the piping system(s). The equipment grounding conductor for the circuit that may energize the piping shall be permitted to serve as the bonding means. The points of attachment of the bonding jumper(s) shall be accessible.

Meaning the grounded cord on the oven or the grounding conductor to the furnace will bond the gas piping.

Originally posted by dirtrider:
I don't think connecting multiple ground clamps to the ufer or ground rod is right but can't find that spelled out.

You can not find it spelled out as it is allowed to do that, it is up to the installer, if you do not like to do it that way you do not have to.

On the other hand you can not fail an inspection if you have multiple clamps on an electrode.

If you have access to the NEC handbook, take a look at Exhibit 250.21 they show using multiple ground clamps on an electrode in the picture the electrode happens to be a water pipe but it applies to all electrodes.

The thing to remember is only the wire from the service disconnect to the first electrode is the Grounding Electrode Conductor, only that wire has to be continuous or spliced with a permanent means.

The wires between electrodes are bonding jumpers, take a look here.

250.53(C) Bonding Jumper. The bonding jumper(s) used to connect the grounding electrodes together to form the grounding electrode system shall be installed in accordance with 250.64(A), (B), and (E), shall be sized in accordance with 250.66, and shall be connected in the manner specified in 250.70.

Originally posted by dirtrider:
As for you guys saying the water is a supplimental grounding electrode it cannot be used to suppliment a ground rod of over 25 ohms.

The water pipe must be used if available and it must be supplemented with at least one ground rod.

When using a ground rod that you can not prove has less than 25 ohms of resistance you must add a second rod.

 

[pierre]

Re: multiple ground clamps at grounding electrode

250.53(D) requires the waterpipe to be supplemented with 250.52(A)(2)-(A)(7) ... although a ground rod is the most common type.

If as in one post a concrete encased electrode is used, you will not have to drive groundrod(s)

Pierre

 

[stars13bars2]

Re: multiple ground clamps at grounding electrode

If you use a concrete encased electrode in my jurisdiction you will drive a ground rod. The AHJ does not recognize these as appropriate grounding means. I don't give up without a fight, but after a sit down meeting with the Building Official, I couldn't even convince her that the code required proof of 25 ohms or less on one rod. Her statement was that we can't just require everyone to drive two ground rods. They still inspect and pass one rod installations.

 

[don_resqcapt19]

Re: multiple ground clamps at grounding electrode

One rod is code compliant if you have a concrete encased electrode. There is no requirement even for one rod when using a concrete encased electrode. The only time 250.56 has to be applied is when the rod is used as the only supplement to the metal underground water pipe electrode or when the rod is the only electrode for the service.
Don

 

[ryan_618]

Re: multiple ground clamps at grounding electrode

Hi Don. While I agree with your statement, I think that it is worth addindg that the resistance must also be met if using a driven rod as the only grounding electrode for the system.

 

[rasmithircgov.com]

Re: multiple ground clamps at grounding electrode

You can call it one electrode conductor and the rest jumpers or you could call them all electrode conductors, but nothing sercumvents the fact of ART 250.50 Grounding Electrode System.
If available on the premises at each building or structure served, each item in 250.52(A)(1) through (A)(6) shall be bonded together to form the grounding electrode system. In that system if you so choose to call them jumpers as the code does, you may run from electrode to electrode. 250.64 Grounding Electrode Conductor Installation. (F) To Electrode(s). A grounding 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. The grounding electrode conductor shall be sized for the largest grounding electrode conductor required among all the electrodes connected to it.


[ March 23, 2004, 03:24 PM: Message edited by: rasmithircgov.com ]