Ground rod in every light pole?

[marcosgue]

We're doing a parking lot where the electrical design shows 8' copper ground rod in every light pole. My questions are:
1. What is the function of this copper ground rod in every light pole? Is good, bad or doesn't matter install this ground rod in terms of electrical safety?
2. Isn't enough the EGC running with the circuits conductors feeding the light pole providing a ground fault current path to open the circuit in the event of ground fault?
In my understanding the ground rod is not necessary but some expert can clarify this or I'm missing something. Thanks

 

[infinity]

1) Some designers think that they're good for lightning strikes to the pole.

2) Yes, all that is required is an EGC run with the branch circuit to ground the metal parts of the pole. IMO the rods are a waste of money.

 

[ptonsparky]

I made money on every one of those rods! Feeding my kids was not a waste.

 

[winnie]

Here is a discussion that Mike Holt participated in from way back:

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Mike Holt worked his way up through the electrical trade from apprentice electrician through electrical contractor, to become one of the most recognized experts in the world as it relates to electrical power installations. He was a Journeyman Electrician, Master Electrician, and Electrical...

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His opinion was that unless you are designing lightning protection at each pole (which might make sense in Tampa!) the ground rod was unnecessary and a waste.

IMHO I could imagine an installation where you have surge suppression at each pole (to shunt wiring surges to local ground), where the poles themselves are designed as air terminals and down conductors, and where ground rods were used. This would make the poles into part of a proper lightning protection system and might make economic sense in a lightning prone installation. But it would be far in excess of the requirements of the NEC. Also it might be cheaper to just buy appropriate insurance and eat the cost of a lightning strike.

Jon

 

[hillbilly1]

Doesn’t really increase the cost by that much, most people just throw the rod in the concrete of the pole base, since the base is usually 8’ deep, with another couple of feet out of the ground. I would say it helps to a degree, as most lightning damage I see is in the 90’s at the bottom of the pole where it exits to earth.

 

[infinity]

Doesn’t really increase the cost by that much, most people just throw the rod in the concrete of the pole base, since the base is usually 8’ deep, with another couple of feet out of the ground.

Don't you think that a CEE in the 8' of concrete would be better or are you saying that you make a CEE with the 8' rod within the concrete?

 

[jaggedben]

If a 6" diameter steel pole is buried 8ft in the ground, then adding a 1/2" by 8ft ground rod increases the surface area in contact with the earth by only 8.3%. I find it difficult to believe this makes a predictable difference.

 

[jaggedben]

.... I would say it helps to a degree, as most lightning damage I see is in the 90’s at the bottom of the pole where it exits to earth.

How does that location of lightning damage tell you if more grounding would help?

 

[electrofelon]

It's a waste of money plain and simple. It's just idiot designers/engineers who find it easy to spend someone else's money.

 

[drcampbell]

It seems like it would be worth a phone call for clarification.

Replacing an occasional light pole might not be a lot of money compared to the cost of installing ground rods, but it might not be about the poles; they might be providing lightning protection for adjacent structures.

 

[Steve16]

Regardless if they are needed or not. If it's on the engineered drawings it's required.

 

[jaggedben]

Regardless if they are needed or not. If it's on the engineered drawings it's required.

I don't know if an 'electrical design drawing' (OPs words) is the same as an 'engineered drawing'. It makes a difference, to me anyway, if it was stamped by a licensed outside engineer or just drawn up by my fellow employee.

 

[gadfly56]

I don't know if an 'electrical design drawing' (OPs words) is the same as an 'engineered drawing'. It makes a difference, to me anyway, if it was stamped by a licensed outside engineer or just drawn up by my fellow employee.

The problem that could develop is that if those rods are on a drawing that was approved by a permitting authority, they will want to see those rods installed. I addition, if the job was bid with the rods and the contract was signed with the understanding that the project would be built to the drawings, the owner/tenant has a right to the installation as bid, or some money back.

 

[jaggedben]

Well, of course. We don't really know if the OP is in the parking lot installing right now or looking at a design to bid or procure for the job. Hopefully s/he is able to make use of our answers.

 

[hillbilly1]

If a 6" diameter steel pole is buried 8ft in the ground, then adding a 1/2" by 8ft ground rod increases the surface area in contact with the earth by only 8.3%. I find it difficult to believe this makes a predictable difference.

I don’t know where your at where they bury steel light poles, but all I have ever seen is fiberglass, pre cast concrete, or concrete bases with anchor bolts, so don’t know what point is?

 

[hillbilly1]

How does that location of lightning damage tell you if more grounding would help?

40+ years of experience in troubleshooting parking lots, usually a direct hit of lightning blows out the wire at the 90’s because it takes the most direct path to earth. If the pole has a better direct path to earth, less chance of it following the egc back to the service and creating more damage.

 

[jaggedben]

I don’t know where your at where they bury steel light poles, but all I have ever seen is fiberglass, pre cast concrete, or concrete bases with anchor bolts, so don’t know what point is?

Okay, I defer to your experience. The point is simply that the efficacy of a ground rod should be considered in comparison to whatever metal paths to earth (anchor bolts, rebar) that you already have otherwise.

 

[LarryFine]

Sharp angles create impedances to high-frequency currents.

They can even create distortions in audio signals.

 

[winnie]

Okay, I defer to your experience. The point is simply that the efficacy of a ground rod should be considered in comparison to whatever metal paths to earth (anchor bolts, rebar) that you already have otherwise.

But also possibly the position of this grounding electrode. Maybe rather than a 'ground rod' one just needs a small bonded galvanized plate connected to the rebar right at the bottom of the concrete base.

Dunno. It would be nice if we had studies of different installations compared that we could share here.

-Jon

 

[electrofelon]

40+ years of experience in troubleshooting parking lots, usually a direct hit of lightning blows out the wire at the 90’s because it takes the most direct path to earth. If the pole has a better direct path to earth, less chance of it following the egc back to the service and creating more damage.

But if the pole is bolted to anchor bolts and the anchor bolt are embedded in concrete, and the concrete is in the earth what is a ground rod going to add to the party? Some critical thinking is required here.