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

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).]

Yes, very good Q!

Didn't want to ask it myself, because I was afraid of what the answer would be!

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-

I you are considering using the #4 as a
Ground Electrode, section 250-52 (99) will
require 24"

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?

(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-

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.

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.

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-

Rarely do I have a water line for a GE... Usually PVC or black plastic, sometimes I have copper pipe to bond to but not as a GE, but that's about it.

Two ground rods on about 15 to 25' of #4 bare solid Cu... Don't think we can get stranded bare here but I've used it in Wisconsin where we had to go to the water line and to two rods with an unspliced GEC...

Solid does stay put better once in place.

Virgil,

I'm not sure I understand this concept of "staying in place."

If you've properly secured this wire movement shouldn't be a problem. I get a lot of homeowners on this one & generally hand them some staples or straps so they can fix it. 250.64(B)

Can you get a delivery from State Electric? I know they carry stranded. I use stranded to keep out the kinks and it is a whole lot easier to pull through drilled holes in basement ceiling joists.

#4 is required here for a 200a service. Now what do you guys think about if you use conduit (for cosmetic purposes) bonding the conduit on each end to the wire to prevent it from becoming a choke if it was used.

Thanks, everyone. I'm glad that I'm not the only one who feels that this is one of those points of Code that are open to interpretation.

FWIW, I usually try to get the #4 down at least 12" deep, figuring that that'll keep it out of the way of a roto-tiller or lawn aerator.

Smurf, why use metallic conduit? Schedule 80 is the way to go. But if you do use IMC or GRC, bond it at BOTH ends.

Cliff