APB for......'pipe electrode'

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ToolHound

Senior Member
All points bulletin for...Pipe Electrode ( a la 250.52(A)(5) )

What situations call for a 'pipe electrode' ?

Never seen one used; never seen one.

Why would anyone want to use a grounding electrode of pipe (or conduit) instead of using a ground rod ?
(although the Code in the 250.52(A)(5) mention of 'pipe electrode' may be ambigous in that nothing specifies that a 'pipe electrode' be exclusively an electrode, as opposed to something like a 'water pipe' serving as a water pipe AND also serving as an 'pipe electrode'. So is a 'pipe electrode', in 250.52-A-5, an electrode in the sense of a ground rod but is pipe instead of a rod ?).

Code quote:

250.52(A)(5)

Rod and Pipe Electrodes. Rod and pipe electrodes shall not be less than 2.44 m (8 ft) in length and shall consist of the following materials.

(a)
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Grounding electrodes of pipe or conduit shall not be smaller than metric designator 21 (trade size ?) and, where of steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection.

(b)
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Rod-type grounding electrodes of stainless steel and copper or zinc coated steel shall be at least 15.87 mm (5/8 in.) in diameter, unless listed.

--Thanks.
 
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iwire

Moderator
Staff member
Location
Massachusetts
It's just an option, maybe at one time ground rods were not readily available.


It has nothing to do with the water pipe electrode.
 

ToolHound

Senior Member
Does Code say 1/2 in min for listed rod ? ...

Does Code say 1/2 in min for listed rod ? ...

ToolHound said:
Listed rods min 1/2 in diameter ?


Where if anywhere in the Code is 1/2 inch minimum for diameter of listed ground rod specified ? ( 250.52A5 only specifies 5/8 inch minimum diameter but seems to leave open the question of minimum diameter for a 'listed' ground rod ).

( I have a published 'quick quide' that sez 1/2 inch min for listed rod, but I do not see that in the Code ).

Thanks.

Ooops, never mind. The 'half inch' matter actually IS addressed in the 2008 Code (even tho 2011 Code seems different in that regard).

Thanks.
 
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ToolHound

Senior Member
Compare 2008 to 2011...

Compare 2008 to 2011...

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Code quote:

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2008_____ 250.52(A)(5)(b)
(b)
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Grounding electrodes of stainless steel and copper or zinc coated steel shall be at least 15.87 mm (5/8 in.) in diameter, unless listed and not less than 12.70 mm (? in.) in diameter.



2011_____ 250.52(A)(5)(b)
(b)
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Rod-type grounding electrodes of stainless steel and copper or zinc coated steel shall be at least 15.87 mm (5/8 in.) in diameter, unless listed.

.

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Hv&Lv

Senior Member
Location
-
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Engineer/Technician
All points bulletin for...Pipe Electrode ( a la 250.52(A)(5) )

What situations call for a 'pipe electrode' ?

Never seen one used; never seen one.

Why would anyone want to use a grounding electrode of pipe (or conduit) instead of using a ground rod ?
(although the Code in the 250.52(A)(5) mention of 'pipe electrode' may be ambigous in that nothing specifies that a 'pipe electrode' be exclusively an electrode, as opposed to something like a 'water pipe' serving as a water pipe AND also serving as an 'pipe electrode'. So is a 'pipe electrode', in 250.52-A-5, an electrode in the sense of a ground rod but is pipe instead of a rod ?).

Code quote:


--Thanks.

There are lots of them here, on older houses mainly (60's-80's)
 

ToolHound

Senior Member
There are lots of them here, on older houses mainly (60's-80's)

Hv&Lv. Ok. Interesting. Just shows, I guess, things can be different in different places or at differnt points in time. Thanks. --ToolHound

( P.S. -- A 250.52(A)(5) electrode of pipe (or conduit) would seem to offer a possible stong point of having more 'surface area' in contact with the earth. Just a thought. )
 
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don_resqcapt19

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retired electrician
When I started the power company specs for residential services called for 3/4" rigid conduit as the grounding electrode and 1/2" rigid conduit at the grounding electrode conductor to the meter can. The 3/4 was driven into the ground below the meter and the 1/2 was run down to below grade, a ninety bent out to the electrode and wedge clamp that was made for the application was used to connect the two conduits together.
 

ToolHound

Senior Member
When I started the power company specs for residential services called for 3/4" rigid conduit as the grounding electrode and 1/2" rigid conduit at the grounding electrode conductor to the meter can. The 3/4 was driven into the ground below the meter and the 1/2 was run down to below grade, a ninety bent out to the electrode and wedge clamp that was made for the application was used to connect the two conduits together.


don_resqcapt19. That rigid conduit technique, for grounding electrode and GEC, seems like a surefire GES. It would be hard to beat that. It's good to know of the other methods besides grounding rods. Interesting. Thanks. --ToolHound
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I have seen pieces of conduit used as a GE too. Not real common I guess, but I have seen it.

What I don't get is the places where I have seen a ground rod sunk into the ground next to a big chunk of metal conduit that also goes underground. Why not just use the ug conduit as a GE and skip the rod? And since it is there, would it not have to at least be bonded in as part of the GES?
 

iwire

Moderator
Staff member
Location
Massachusetts
I have seen pieces of conduit used as a GE too. Not real common I guess, but I have seen it.

What I don't get is the places where I have seen a ground rod sunk into the ground next to a big chunk of metal conduit that also goes underground. Why not just use the ug conduit as a GE and skip the rod? And since it is there, would it not have to at least be bonded in as part of the GES?

I would be hard pressed to find a section prohibiting that I doubt many inspectors would accept a conduit being used as a raceway to also serve as an electrode.
 

GoldDigger

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I would be hard pressed to find a section prohibiting that I doubt many inspectors would accept a conduit being used as a raceway to also serve as an electrode.

An electrode may well have currents flowing through it that cause it to corrode more rapidly than it would just sitting isolated in the ground. At some point you replace it if necessary and if anyone notices. :)
A conduit is intended to protect the wires it contains, rather than being deliberately consumed, and is a lot harder to replace.

Now, since with bonding the same voltage/shared current will appear on both the conduit and the electrode, you may have some problems in some soil types. But you overcome that by using a protective layer on the outside of the conduit, and there goes the ability to serve as a ground electrode.

Rather than do a site by site evaluation, I can see an inspector just treating it as general rule, justified by code or not.
 

ToolHound

Senior Member
RMC coated for corrosion protection ?

RMC coated for corrosion protection ?

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Code quote:
.
.
250.52(A)(5)

(5) Rod and Pipe Electrodes. Rod and pipe electrodes shall not be less than 2.44 m (8 ft) in length and shall consist of the following materials.

(a) Grounding electrodes of pipe or conduit shall not be smaller than metric designator 21 (trade size ?) and, where of steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection.

(b) Rod-type grounding electrodes of stainless steel and copper or zinc coated steel shall be at least 15.87 mm ( 5/8 in.) in diameter, unless listed.

Regarding 250.52(A)(5)(a), as quoted above, does rigid RMC conduit satisfy the condition, “…where of steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection” ?

In other words, if RMC is 'steel', is RMC’s outer surface galvanized or otherwise metal-coated for corrosion protection ?

Thanks.
 
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don_resqcapt19

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Location
Illinois
Occupation
retired electrician
Regarding 250.52(A)(5)(a), as quoted above, does rigid RMC conduit satisfy the condition, ??where of steel, shall have the outer surface galvanized or otherwise metal-coated for corrosion protection? ?

In other words, if RMC is 'steel', is RMC?s outer surface galvanized or otherwise metal-coated for corrosion protection ?

Thanks.
Standard rigid conduit meets the requirements of the code for use as a grounding electrode.
 

don_resqcapt19

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Location
Illinois
Occupation
retired electrician
don_resqcapt19. That rigid conduit technique, for grounding electrode and GEC, seems like a surefire GES. It would be hard to beat that. It's good to know of the other methods besides grounding rods. Interesting. Thanks. --ToolHound
The current code does not permit the use of conduit as the grounding electrode conductor. 250.62 says the GEC must be copper, aluminum or copper clad aluminum.
 

ToolHound

Senior Member
The current code does not permit the use of conduit as the grounding electrode conductor. 250.62 says the GEC must be copper, aluminum or copper clad aluminum.



don_resqcapt19. Thanks for that important reminder. Same as you said, quote:

NEC:

Chapter 2
Wiring and Protection
ARTICLE 250 Grounding and Bonding
III. Grounding Electrode System and Grounding Electrode Conductor

250.62 Grounding Electrode Conductor Material. The grounding electrode conductor shall be of copper, aluminum, or copper-clad aluminum. The material selected shall be resistant to any corrosive condition existing at the installation or shall be protected against corrosion. The conductor shall be solid or stranded, insulated, covered, or bare.


Also, the 18 inch rule of 250.64(A), for aluminum or copper-clad aluminum, quoting NEC:

250.64 Grounding Electrode Conductor Installation.
Grounding electrode conductors at the service, at each building or structure where supplied by a feeder(s) or branch circuit(s), or at a separately derived system shall be installed as specified in 250.64(A) through (F).

(A) Aluminum or Copper-Clad Aluminum Conductors. Bare aluminum or copper-clad aluminum grounding electrode conductors shall not be used where in direct contact with masonry or the earth or where subject to corrosive conditions. Where used outside, aluminum or copper-clad aluminum grounding electrode conductors shall not be terminated within 450 mm (18 in.) of the earth.
 

kwired

Electron manager
Location
NE Nebraska
don_resqcapt19. That rigid conduit technique, for grounding electrode and GEC, seems like a surefire GES. It would be hard to beat that. It's good to know of the other methods besides grounding rods. Interesting. Thanks. --ToolHound
Concrete encased electrodes are what is hard to beat IMO. If they are present other "made" electrodes are not even required.
 

ToolHound

Senior Member
Concrete encased electrodes are what is hard to beat IMO. If they are present other "made" electrodes are not even required.


Kwired. Thanks. The 'Ufer Ground' ( aka 'concrete encased electrode')...a fascinating history and practical science explanation of the 'Ufer Ground' are written up at
http://en.wikipedia.org/wiki/Ufer_ground.
The high pH of concrete, and the 'doping' effect of concrete on adjacent soil, are cited as positive factors in the well regarded effectiveness of a concrete encased electrode. Concrete is more than just a foundation.


document.php

I
Exhibit 250.23 An example of a concrete-encased electrode that is required to be incorporated into the grounding electrode system. The horizontally installed reinforcing rod located near the bottom of the footing must consist of either a single 20-ft continuous section or multiple sections connected together in a 20-ft continuous length.
 
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ToolHound

Senior Member
Concrete encased electrodes are what is hard to beat IMO. If they are present other "made" electrodes are not even required.


The good effect of concrete-encasement of a GES electrode leads to me to another idea. I am drawn to the possible gain of encasing even the garden variety rod-type electrodes in concrete. Instead of driving the grounding rod into the ground, it would seem a fair bet that grounding rod conductivity-to-earth could be improved by auger'ing or otherwise digging a big hole--something like 10 feet deep by 12-18 inches diameter. And burying most of the rod-type electrode in concrete. Obvioulsly this approach could be somewhat at odds with cost control. But I could imagine any otherwise anemic rod-type electrode conductivity-to-earth being beefed up by this approach. More electrode conductivity to earth. ???? Just a thought...espescially for anyone living in Lightning-ville, USA, or for anyone who especially values additional, robust GES conductivity to earth.
 

GoldDigger

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Exhibit 250.23 An example of a concrete-encased electrode that is required to be incorporated into the grounding electrode system. The horizontally installed reinforcing rod located near the bottom of the footing must consist of either a single 20-ft continuous section or multiple sections connected together in a 20-ft continuous length.

The illustration is potentially misleading in a way that has come up in other threads. You can only count a ufer if it runs through a wall footing rather than just through a flat foundation slab. The rods that go through the slab add to the quality of the ground as long as there is not a waterproofing membrane under it, but it is the footing portion that is mandatory.
 
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