Auxiliary grounding electrode and light poles

[mshields]

I'd like to get opinions on the practice of providing aux ground rods at outdoor light poles. I'm talking about installations that are perfectly within the boundaries of the NEC. i.e. the poles are bonded. But for which an aux ground rod is connected to the equipment (the pole).

The rational is that in the event of a lightning strike, most of the energy will go to ground and not into the facility from where the pole is fed.

Of course on the flip side, the ground rod does a nice job of picking up any nearby lightning strikes and carrying that energy into the building.

I'm trying to determine what the best practice is. Any input is appreciated!!!

Mike

 

[George Stolz]

Of course on the flip side, the ground rod does a nice job of picking up any nearby lightning strikes and carrying that energy into the building.

Why would you say that?

 

[mshields]

ground rods and light poles

ground rods and light poles

It's an argument I've heard made. Not sure I buy it at all. After all, if it's true, what's to prevent the required and much more substantial grounding electrode system from causing the same problem?

Mike

 

[dereckbc]

IT is debatable but a question and comment back at you.

How if the pole mounted supported?

If it has a concrete pad with anchor bolts and rebar, a ground rod adds no value as the Ufer formed by the pad is way more effective.

 

[220/221]

If it has a concrete pad with anchor bolts and rebar, a ground rod adds no value as the Ufer formed by the pad is way more effective.

I concur. 6' of concrete and steel in the ground seems substantial enough.

I have had them spec'd out with ground rods 20" away.

 

[benaround]

Trouble is if ground rod is not speced your gambaling that the steel cage

gets tied to the anchor bolts, around this area the anchor bolts are the last

thing installed after the concrete is poured and your lucky if they get put in

right, never mind having a solid wire connected to them to confuse those

guys even more.

 

[iwire]

Trouble is if ground rod is not speced your gambaling that the steel cage

gets tied to the anchor bolts, around this area the anchor bolts are the last

As long as the steel anchor bolts are connected to the pole and poured into the concrete that is in contact with the earth you will have a lower resistance connection from pole to earth then a rod can ever provide.

 

[infinity]

As long as the steel anchor bolts are connected to the pole and poured into the concrete that is in contact with the earth you will have a lower resistance connection from pole to earth then a rod can ever provide.

I agree, add the rods if it helps you to sleep better at night but remember that they will be doing next to nothing.

 

[831]

As long as the steel anchor bolts are connected to the pole and poured into the concrete that is in contact with the earth you will have a lower resistance connection from pole to earth then a rod can ever provide.

Can you believe there are PEs that still pound their fists that this type of app must happen??? Talk about perpetuating bad habits and wasted money!

 

[LawnGuyLandSparky]

Next they'll demand a deep earth ground!

 

[brian john]

Can you believe there are PEs that still pound their fists that this type of app must happen??? Talk about perpetuating bad habits and wasted money!

Not saying I would or would not drive an additional electrode at a light pole, but: But on the other side of this issues I have heard the following arguments.

1. Have electrodes been proven to be effective when utilized with a lightning protection system (LPS)?

2. Are not additional electrodes, when utilized with a LPS?

3. When lightning hits a tree and it splits this is due to super heating of moisture in the tree escaping as steam, would not this happen with a light pole base? Might an additional electrode minimize this?

Do you have scientific evidence of your stance? I am not sure there is scientific evidence in favor of installing additional electrodes just past use that some see as proff.


As for lighting a impulse entering a building, I had a facility I did an post equipment damage inspection at a facility, they had installed a truly IG to a piece of equipment. Setting on rubber mats, EMT to PVC coupler no EGC, then a grounding electrode to to 10" ground rods, lighting hit within 5 feet of the electrodes, fried the multi million dollar equipment, scorched the PVC coupler, and there was damage at other locations along the path of the EMT.

 

[831]

Do you have scientific evidence of your stance?

Straight answer: no.

Nor have I seen anything compelling enough to have driven me toward include such in my designs.

Caveat: lightning isn't the big deal here in Utah like states such as FL (were I'm from). Nevertheless it's a topic of interest for me.

 

[coulter]

There has been a large string on one of mike's topics within the last couple on months. I'd recommend you read that.

There were a bunch of interesting comments. One poster insisted the driven ground had a lower impedance to lightning strikes that the steel and concrete foundation. Another (or the same one) stated that without the ground rod a lightning strike would split the foundation - with the ground rod, no damage to the to the foundation.

All of the ground rod proponents had anecdotal information showing the damage decreases when ground rods were installed.

What do I think? Mostly mirrors one of our more knowledgable posters - Drive'em if it makes you feel better.

As for the anecdotal information - Absent a peer reviewed study, people tend to see what they want to see.

carl

 

[brian john]

Absent a peer reviewed study, people tend to see what they want to see.

I agree 100% and wish this was review was available.

In general it has been my expierence, not my belief.

1. If there was some sort of grounding issue most people want an extra rod or two, in lieu of actually locating the issue.

2. If a site had 100 rods and never gets hit by lighting, all future sites will get 100 rods.

3. When in doubt drive an extra rod.

And I bet the ground rod manufactures are not fighting this style of installation.

 

[boboelectric]

I've seen a building with up to standard rooftop lightning protection a 100 feet from an old pine tree that got blasted by lightning.

 

[coulter]

I've seen a building with up to standard rooftop lightning protection a 100 feet from an old pine tree that got blasted by lightning.

Give us some signifigance. I'm not being facetious, I don't see an obvious connection.

carl

 

[George Stolz]

Based on that event, two people could look at the information two different ways:

• The lightning protection system prevented the lightning from hitting the building.
• Lightning is very unpredictable, may not strike the highest point in an area, and is not necessarily predictably drawn to air terminals (lightning rods).

Open question to all, which guy are you?

 

[coulter]

...Open question to all, which guy are you

Since I don't currently see the connection, one of the following two:

... If a site had 100 rods and never gets hit by lighting, all future sites will get 100 rods. ...

...Absent a peer reviewed study, people tend to see what they want to see. ...

carl

 

[mshields]

Interesting input

Interesting input

To the poster who indicated with some amusement and disbelief that PE's are still driving ground rods in these applications. I think, based on the, preponderance of responses, the practice can be deemed possibly helpful and in no way harmful. No one is suggesting it is code required.

I do think the point about a base with rebar all properly interconnected, no doubt, provides a far better electrode (of the Ufer variety) than the ground rod is a good one. It probably renders the ground rod insignificant.

Still, I can't see the connections within the concrete. I can certainly see the connection to a ground rod. I like what Coulter said; if it makes you feel better put em in. And I'm thinking that it does.

Mike

 

[kingpb]

Ground rods driven at light poles, where no other ground grid is present, will help to keep a pole from becoming charged, due to static build-up, especially when they are near HV power lines. Nothing to do with lightning. it is for safety to eliminate touch potentials.