Streetlight gec

wyreman

Senior Member
Location
SF CA USA
We are installing many new street poles and there are tremendous amount of underground utilities in the area. Instead of driving a ground At each pole the idea is to put 20 feet of bare number eight at the bottom of the footing using it as uffer grnd.

Of course there's an appropriately sized grounding equipment conductor Back to xo/service.

The question is is a code compliant to substitute uffer ground for the rod at individual poles.
It's more expensive there is also ground disruption anyway to get the pole but this will save popping some geothermal or high voltage lines.

Thx
 

kwired

Electron manager
Location
NE Nebraska
We are installing many new street poles and there are tremendous amount of underground utilities in the area. Instead of driving a ground At each pole the idea is to put 20 feet of bare number eight at the bottom of the footing using it as uffer grnd.

Of course there's an appropriately sized grounding equipment conductor Back to xo/service.

The question is is a code compliant to substitute uffer ground for the rod at individual poles.
It's more expensive there is also ground disruption anyway to get the pole but this will save popping some geothermal or high voltage lines.

Thx
First as mentioned the poles do not necessarily require a grounding electrode. If someone requires one because it is a separate structure they still are typically fed by a single branch circuit or a multiwire branch circuit and still do not have a NEC requirement for a grounding electrode.

As far as the effectiveness of putting 20 feet of copper in the base - I don't think it will be nearly as effective all coiled up (assuming that is what you are doing) as it is stretched out the full 20 feet. The amount of surface area of concrete contacting the earth is what lowers the resistance and the NEC has determined that you need 20 feet minimum to reliably have a low enough resistance to be effective. Coiling up the copper gives you 20 feet of copper but does not increase the amount of contact with earth, you could easily have about same resistance as if you only installed 5 feet of copper. JMO.
 

kwired

Electron manager
Location
NE Nebraska
Coiled or stretched Still more surface area than a ground rod isn't it?
more copper yes - but still same concrete in contact with earth.

You may have some lower resistance from more copper to concrete contact but you are trying to acquire low resistance to earth not just the copper or concrete.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
We are installing many new street poles and there are tremendous amount of underground utilities in the area. Instead of driving a ground At each pole the idea is to put 20 feet of bare number eight at the bottom of the footing using it as uffer grnd.

Of course there's an appropriately sized grounding equipment conductor Back to xo/service.

The question is is a code compliant to substitute uffer ground for the rod at individual poles.
It's more expensive there is also ground disruption anyway to get the pole but this will save popping some geothermal or high voltage lines.

Thx
IMO this falls under the installation of an auxiliary grounding electrode and the NEC doesn't really care what you install.
 

tom baker

First Chief Moderator
Staff member
For your Ufer ground to be acceptable per the NEC it has to meet the requirements given in 250.52(A)(3). A ufer ground is intened to go in a footer. A pole foundation is stretching the requirements a bit.
Having said that I have a study that shows the concrete in a pole base makes a pretty good ground as the concrete is fairly conductive. One issue that comes up is in a lightning strike the energy will blow apart the concrete if the rebar connections are loose.

There is no requirement for a ground rod at a light pole, its done because the specs you have were copied from someone else, and nobody knows how it got started.

Its almost like ground up or ground down.
 

kwired

Electron manager
Location
NE Nebraska
For your Ufer ground to be acceptable per the NEC it has to meet the requirements given in 250.52(A)(3). A ufer ground is intened to go in a footer. A pole foundation is stretching the requirements a bit.
Having said that I have a study that shows the concrete in a pole base makes a pretty good ground as the concrete is fairly conductive. One issue that comes up is in a lightning strike the energy will blow apart the concrete if the rebar connections are loose.

There is no requirement for a ground rod at a light pole, its done because the specs you have were copied from someone else, and nobody knows how it got started.

Its almost like ground up or ground down.

A pole foundation is same thing, but is usually vertical instead of horizontal. The thing that matters the most is how much surface is in contact with earth. That copper embedded in the concrete will have a zone or gradient around it, and so will the concrete. If you coil the copper up you have that zone overlapping itself instead of stretched out for maximum effect, doesn't matter if it is in a pole base or a footer of a building, it needs stretched out to take advantage of that zone to get lower resistance to earth.
 

Stevareno

Senior Member
Location
Dallas, TX
IMO this falls under the installation of an auxiliary grounding electrode and the NEC doesn't really care what you install.
That's what I think too.

I've seen many prints that specify the GEC in a pole base. A bare solid #8 run down through the form tied to the rebar with at least 5' of coil at the bottom. Inspectors here don't have a problem with it.
 
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