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#9787 - 05/13/02 06:40 PM burial depth - GEC
amp-man Offline
Member

Registered: 06/23/01
Posts: 144
Loc: Sacto, California US of A
Hi y'all,

A simple question:

When using 4 AWG (copper, stranded) as a grounding electrode conductor, what burial depth is required? This is for a residential occupancy.

Is it 24 inches, based on column 1 (direct burial cables or conductors) and the first row ("all locations not specified below") (the table is for "0 to 600 volts")?

Would appreciate your views.

Cliff

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#9788 - 05/18/02 07:07 AM Re: burial depth - GEC
Frank Cinker Offline
Member

Registered: 07/29/01
Posts: 317
Loc: Pennsylvania
Good question. I've never even thought of it before. I couldn't imagine a GEC being buried 24 inches. For example, if a driven ground rod is located several feet from a house I usually buried the GEC 6 inches if not less at times. Perhaps an electrical inspector can address this question.

[This message has been edited by Frank Cinker (edited 05-18-2002).]

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#9789 - 05/18/02 07:43 AM Re: burial depth - GEC
sparky66wv Offline
Member

Registered: 11/17/00
Posts: 2339
Loc: West Virginia
Yes, very good Q!

Didn't want to ask it myself, because I was afraid of what the answer would be!
_________________________
-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

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#9790 - 05/18/02 09:19 AM Re: burial depth - GEC
motor-T Offline
Member

Registered: 11/10/01
Posts: 293
Loc: Girard, Ohio, USA
Why would you use No.4 to a ground rod ?
...And would it not be No.4 to the water line if one exists?
As far as burial goes it must be below the earth, is there a depth for it after all it must come out of the ground to go to the meter base or service panel.

-Mark-

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#9791 - 05/18/02 09:39 AM Re: burial depth - GEC
Bob Offline
Member

Registered: 02/05/02
Posts: 182
Loc: Mobile, AL, USA
I you are considering using the #4 as a
Ground Electrode, section 250-52 (99) will
require 24"

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#9792 - 05/18/02 10:28 AM Re: burial depth - GEC
sparky66wv Offline
Member

Registered: 11/17/00
Posts: 2339
Loc: West Virginia
I use #4 bare solid Cu because no conduit is required.... Uh, right?

#6 isn't significantly cheaper, and #4 just seems to be the tradition for 200A services... Any better arguments either way?

_________________________
-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

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#9793 - 05/18/02 11:15 AM Re: burial depth - GEC
motor-T Offline
Member

Registered: 11/10/01
Posts: 293
Loc: Girard, Ohio, USA
(A) Connections to Rod, Pipe, or Plate Electrodes. Where the grounding electrode conductor is connected to rod, pipe, or plate electrodes as permitted in 250.52(A)(5) or 250.52(A)(6), that portion of the conductor that is the sole connection to the grounding electrode shall not be required to be larger than 6 AWG copper wire or 4 AWG aluminum wire.

My understanding of this is that the resistance of the ground rod itself is higher than the no.4 it self and would not improve the resistance of the system.
-Mark-

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#9794 - 05/19/02 06:36 AM Re: burial depth - GEC
Electric Eagle Offline
Member

Registered: 04/20/02
Posts: 928
Loc: Alpharetta, GA
Mark, You're right about #4 being larger than required, but I know in my area you can't pass inspection with #6 on a 200 amp system so we just automatically use #4 solid CU.

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#9795 - 05/19/02 08:58 AM Re: burial depth - GEC
Tom Offline
Member

Registered: 01/01/01
Posts: 1069
Loc: Shinnston, WV USA
When I inspect service entrances in the Allegheny Power service area, I'll accept just about any depth that will cover the conductor & won't get washed away by the rain.

What most guys do is about 1 shovel in depth, about 6 inches.

It could be a judgement call about using #6, since it is only allowed where it is "free from exposure to physical damage." Whereas #4 can be used with no protection if it is not "exposed to severe physical damage."

I've seen some make an arguement for burial at 24" based on column 1 of Table 300.5 After all, this is a conductor, and it operates within the 0-600 volt parameters of the table. If I'm ever forced into burying the grounding electrode conductor that deep, I'll sub out that phase of the work, too much shovel time.
_________________________
Few things are harder to put up with than the annoyance of a good example.

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#9796 - 05/19/02 09:53 AM Re: burial depth - GEC
motor-T Offline
Member

Registered: 11/10/01
Posts: 293
Loc: Girard, Ohio, USA
Eagle:
I see where you and Sparky66wv bboth use no.4 solid, I have never used solid for fear of getting 'un-removable' kinks in it so I always use stranded. Now I can understand the following the contour of the building better wiht solid, is this why ? But what about going to the water line ? A lot of the times I have to go across a basement wiht the cable to get to the water-meter do you use solid for this and how does it work out for you.???
I will try anything if it helps the job run smoother, alot of time i will mount some 1/2 pvc on the side of the basement wall and drop the no.6 to the ground-rods that way if it helps protect it on a long run, but generally if I can I will drill a hole close to the dirt level and snake the ground wire out that way, then plug it up with 'Duck' seal.
-Mark-

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