residential bonding

17481 Views 27 Replies 9 Participants Last post by waco, Mar 9, 2008

Bkessler

Discussion Starter · Feb 26, 2008

I was told today by an inspector that my #4 solid bare copper grounding electrode conductor "had to be protected" and suggest I use the mc style #4. He also said that the cold water bond" had to be in the front yard only and within five feet of the door". My #4 goes from the bottom of the All in one surface mt double meter/double 100 amp main about 20 inches down through the bond of the crawlspace 30 feet stapled along the top plate of the foundation to the hose bib in the back where it comes out right on top of the water pipe in the back yard andhits a cold water clamp about 20 inches down which 10 are underground, to the ground rod and up to an acorn style connector right at ground level. He passed it and said next time do it with the Mc #4 the cold water clamp in the front yard and the ground rod at the panel. Which I have no problem with it's just randomly out of the blue because I have done variations of the same installation for years with out a peep. Also, what are some of the ways y'all do your grounding for service changes and upgrades?

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Speedy Petey

· #2 · Feb 26, 2008

I guess he is applying 250.64(B), although I do feel he is grasping at straws with this one.

250.64 Grounding Electrode Conductor Installation

(B) Securing and Protection Against Physical Damage Where exposed, a grounding electrode conductor or its enclosure shall be securely fastened to the surface on which it is carried. A 4 AWG or larger copper or aluminum grounding electrode conductor shall be protected where exposed to physical damage. A 6 AWG grounding electrode conductor that is free from exposure to physical damage shall be permitted to be run along the surface of the building construction without metal covering or protection where it is securely fastened to the construction; otherwise, it shall be in rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, electrical metallic tubing, or cable armor. Grounding electrode conductors smaller than 6 AWG shall be in rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, electrical metallic tubing, or cable armor.

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waco

· #3 · Feb 27, 2008

For 100 amp services, #6 to the cold water pipe its closest point on entry into the house, usually clamped on both sides of the meter if the meter is in the house. #4 if 200 amp or bigger.

In both, another #6 to ground rod, usually near the meter, out far enough to clear the footer. I usually bury the top of the rod and the wire down about 6 inches.

I staple the primary going to the water pipe, but the one going to the ground rod is usually held down with clamps.

I have run the wire to the ground rod down the conduit for the underground service feed and to the ground rod basically driven in the same ditch dug for the lateral. I usually leave it uncovered until inspected.

I have never had an inspector tell me to use armored wire.

Speedy Petey

· #4 · Feb 27, 2008

waco said:
For 100 amp services, #6 to the cold water pipe its closest point on entry into the house, usually clamped on both sides of the meter if the meter is in the house. #4 if 200 amp or bigger.

The water bond is sized according to the size of the SEC's. We use T250.66 for this, taken from 250.104(A)(1).

For 100A this is typically #8, and for 200A it is #4.
320A would likely be #2cu and a true 400A would be 1/0cu.

leland

· #5 · Feb 27, 2008

WOW, They still use copper pipes in houses? Thats cool.
We don't any more (than needed) it gets ripped out 10 mins after you leave the job!!

I just drop mine down in sch 40 pvc. and their always happy.

waco

· #6 · Feb 27, 2008

Yes, but the vast majority of my service upgrades/replacements are residential, 100 , 200, or 400 amp, so our general use is #6 and #4 bare copper.

Yes, we still have copper in places where we are doing upgrades/replacements, but more and more new construction is using plastic. In that case, two ground rods and wire sized according to the service.

Speedy Petey

· #7 · Feb 27, 2008

waco said:
Yes, but the vast majority of my service upgrades/replacements are residential, 100 , 200, or 400 amp, so our general use is #6 and #4 bare copper.

I wasn't trying to be a jerk by correcting you. What we use day to day, and what is code required can be very different things.

I also only stock and use #6 and #4. I can't remember the last 100A service I did so carrying #8 makes no sense. The odd 100A bond I do need to do I also just use #6 because I have it.

I DO use #8TW solid for pool bonding but that's a different thing.

waco

· #8 · Feb 27, 2008

I use #8 for general bonding, but the thought nags at me that #6 is as small as we go for grounding services. I still see old, armored #8, but usually it is left over from an older, replaced service, probably fuses.

Still, nobody ever told me to use armored grounding wire.

Speedy Petey

· #9 · Feb 27, 2008

waco said:
Still, nobody ever told me to use armored grounding wire.

Me neither. Especially for #4.

leland

· #10 · Feb 27, 2008

Me Too, #6 Is the smallest I use. Gas is big in the rural areas here so 100A are still common (on the spec places). #6 has more uses so thats what I drag around. Solid 8 for the pool stuff of course.

And yes, we still have a ton of hard copper piped houses here as well, but the new ones, all plastic, biggest issue is the new plastic encased Gas lines.This is still a chalenge from town to town for me.

Wireless

· #11 · Feb 27, 2008

Was this a remodel or new construction? In LA we are only required to bring it within 5' of entering the building (not the entrance of the building) on new construction, on remodels/service upgrades it is the closest cold water line.

Bkessler

Discussion Starter · #12 · Feb 27, 2008

This was in the city of orange and it was a house that was knob and tube. This is also the same house if you remember from an earlier post that I had to put a double meter in because edison wont allow two service drops on the same property for th eback house . One thing after another. Oh yeah, in Santa Ana all new panels have to be overhead and underground in case they put all the utilities underground some day

Absolutetruthz

· #13 · Mar 2, 2008

waco said:
Yes, but the vast majority of my service upgrades/replacements are residential, 100 , 200, or 400 amp, so our general use is #6 and #4 bare copper.

Yes, we still have copper in places where we are doing upgrades/replacements, but more and more new construction is using plastic. In that case, two ground rods and wire sized according to the service.

Is that an NEC requirement (two ground rods) if there is not metal water pipe? I dont remember that one.

waco

· #14 · Mar 2, 2008

I don't either. It is what the AHJ wants, maybe due to local soil conditions and the requirement that the resistance be 25 ohms or less. Funny thing is, I did a job that involved two different AHJs and both services required two ground rods because there was no water pipes. One AHJ was okay with one #4 conductor running from the 200 amp service to the first electrode, then on to the second. The other AHJ wanted two separate conductors from the 200 amp service, one to each ground rod.

"Not a problem," say I.

RePhase277

· #15 · Mar 2, 2008

Absolutetruthz said:
Is that an NEC requirement (two ground rods) if there is not metal water pipe? I dont remember that one.

No, two ground rods just lets you side step the requirement of 250.56 of 25 ohms or less. The code says one rod must be 25 ohms or less. If not, you must use an additional rod, but it doesn't state an ohm value.

The cold water electrode is primary. It must be supplemented by another electrode, not necessarily a rod, pipe, or plate. The ufer will suffice.

InPhase277

Speedy Petey

· #16 · Mar 2, 2008

InPhase277 said:
The cold water electrode is primary. It must be supplemented by another electrode, not necessarily a rod, pipe, or plate. The ufer will suffice.

Just to add, a rod is never required. In a home with a non-metallic water feed line it is possible that a Ufer be the ONLY electrode.

waco

· #17 · Mar 2, 2008

In this part of the country, water pipes and ground rods are by far the majority grounding technique. I have encountered UFer grounding ONLY on a couple of government jobs.

Life safety grounding is the NEC requirement while UFers are often for reducing "noise" often induced by radar sites.

It is true, ground rods aren't the only type of secondary grounding electrode, but around here, they are the vast majority in both commercial and residential.

Speedy Petey

· #18 · Mar 2, 2008

waco said:
Life safety grounding is the NEC requirement while UFers are often for reducing "noise" often induced by radar sites.

Care to explain this a little better.
Are you saying ground rods are "life safety grounding"???

I agree about ground rods being the vast majority of electrodes being used. Since we are also not under 2005-8 we are not required to use ufers.
For those who are under 2005-8 they are ALL that is typically required.

waco

· #19 · Mar 3, 2008

Speedy Petey said:
Care to explain this a little better.
Are you saying ground rods are "life safety grounding"???

I agree about ground rods being the vast majority of electrodes being used. Since we are also not under 2005-8 we are not required to use ufers.
For those who are under 2005-8 they are ALL that is typically required.

As I wrote, I've encountered it only in a couple of government jobs which specified the grounding system. Around here, the soil is deep and fairly conductive and not at all corrosive, so ground rods work well and long.

We are under 2005-8. I don't have the 2008 book, but I have the 2005 and I've sure passed a lot of inspections since it was adapted.

I don't know about others, but I seriously doubt the validity of any tests for ground rod conductivity, but I agree with the notion that a couple of grounds, done correctly, is as good as it gets.

Speedy Petey

· #20 · Mar 3, 2008

My point was as of 2005, you are required to install a CCE (Ufer) if any rebar exists at all.
This is a change in wording in 2005 from "if available" to "that are present". So if rebar is present you MUST use it as an electrode. Same as a metallic water line.
In this case, with a non-metallic water line, no other electrodes are required since none "exist".

If your AHJs are not enforcing a mandatory Ufer then it is either a local amendment, or they simply don't care to enforce it.

Here is the code section (which I know you have) and the Handbook commentary in blue.

250.50 Grounding Electrode System
All grounding electrodes as described in 250.52(A)(1) through (A)(6) that are present at each building or structure served shall be bonded together to form the grounding electrode system. Where none of these grounding electrodes exist, one or more of the grounding electrodes specified in 250.52(A)(4) through (A)(7) shall be installed and used.

Commentary:
Section 250.50 introduces the important concept of a ``grounding electrode system,'' in which all electrodes are bonded together, as illustrated in Exhibit 250.21. Rather than total reliance on a single grounding electrode to perform its function over the life of the electrical installation, the NEC encourages the formation of a system of electrodes ``that are present at each building or structure served.'' There is no doubt that building a system of electrodes adds a level of reliability and helps ensure system performance over a long period of time.

This section was revised for the 2005 Code to clearly require the inclusion of a concrete-encased electrode, described in 250.52(A)(3), in the grounding electrode system for buildings or structures having a concrete footing or foundation with not less than 20 ft of surface area in direct contact with the earth. This requirement applies to all buildings and structures with a foundation and/or footing having 20 ft or more of 1/ 2 in. or greater electrically conductive reinforcing steel or 20 ft or more of bare copper not smaller than 4 AWG. However, an exception does exempt existing buildings and structures where access to the concrete-encased electrode would involve some type of demolition or similar activity that would disturb the existing construction. Because the installation of the footings and foundation is one of the first elements of a construction project and in most cases has long been completed by the time the electric service is installed, this revised text necessitates an awareness and coordinated effort on the part of designers and the construction trades in making sure that the concrete-encased electrode is incorporated into the grounding electrode system.

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