Ground rods for parking lot poles

[quogueelectric]

While wiring some parking lot pole lights a thought crossed my feeble little mind.
The pole mfg had 2 tapped holes of different sizes on thier little ground flange inside the handhole. Why 2 holes??
Ther pole bases had groundrod wires pre poured into the concrete. As I was splicing out the poles I thought that the groundrod may have been more of a lightning protection thing at each pole and would it carry the lightning back into the building if struck.

Now If I splice all of the grounds together I had aprox 24 poles now I am adding a field of 24 groundrods all connected together carried back to the service equipment which may verry well be a much better ground Than the building ground.
Which in itself may or may not increase or decrease the chanses of being hit by lightning in the first place.
Any thoughts on the subject??

 

[ultramegabob]

many people feel that groundrods at lightpoles are a waste of money, I think it is cheap insurance myself, I may be wrong, but I feel its better to error on the side of caution....

 

[quogueelectric]

many people feel that groundrods at lightpoles are a waste of money, I think it is cheap insurance myself, I may be wrong, but I feel its better to error on the side of caution....

Do you have any concerns about a lightning strike carrying the lightning into a perfectly happy premise wiring system?

 

[stickboy1375]

Do you have any concerns about a lightning strike carrying the lightning into a perfectly happy premise wiring system?

Sure, but the concrete that the light pole is bolted to will do the same thing as a ground rod.

 

[peter d]

Sure, but the concrete that the light pole is bolted to will do the same thing as a ground rod.

Uh oh....there's that common sense again. :roll:

 

[Buck Parrish]

Do you have any concerns about a lightning strike carrying the lightning into a perfectly happy premise wiring system?

No, It would be more likely to go to ground. It would be closer then the utilities ground. Even through the ground to a metal water pipe.

It would fizzle out by the time it got to the bottom of the light pole pass the grd. rod and perhaps numerous grd. rods. The wire couldn't carry the amount of current back to the premises. It would melt.

It could happen. It's not likely.

 

[stickboy1375]

Uh oh....there's that common sense again. :roll:

You mean the 8ft ground rod isnt the only thing lightning seeks? :grin:

 

[quogueelectric]

You mean the 8ft ground rod isnt the only thing lightning seeks? :grin:

I think they drove 10s a friend of mine just took a grounding class and told me they knocked 10 ohms off the ground impedance by using a hypressed compression connector instead of an acorn nut.
EVEN IF the lightning was say 100kv and most of it dissipated to the 24 10' ground rods lets say a meager 1kv or so traveled back up the feeder ground backinto the building to the service bonded to the source and the building ground.
A meager 1000v can do a lot of damage I think.

 

[quogueelectric]

Sure, but the concrete that the light pole is bolted to will do the same thing as a ground rod.

10 foot by about 30" round at top 3', square 7' burried, 25' steel poles Cooper brand 400w metal halide. Heavy as a dog. Sorry Frisbee. Kind iof like a small ufer ground about 2-3 tons in contact with the ground its not gonna blow away.

 

[stickboy1375]

a friend of mine just took a grounding class and told me they knocked 10 ohms off the ground impedance by using a hypressed compression connector instead of an acorn nut.

10 ohms off of what? 1000? 500? Do I think lower is better to prevent surface arcing? Sure, do I think a rod is better than a concrete footing? No way.

 

[quogueelectric]

Uh oh....there's that common sense again. :roll:

24 10'ground rods plus 24 mini ufers all in parallel to ground. Question of the day is where is the building current imbalance going to go to get back to the source?? Lots of simultaneous stuff going on here and as one changes the whole picture changes too, kind of like a calculus exam. :smile: Lots of paralell paths and the impedance keeps going down but where are the electrons flowing?? Dont walk your dog here.

 

[quogueelectric]

10 ohms off of what? 1000? 500? Do I think lower is better to prevent surface arcing? Sure, do I think a rod is better than a concrete footing? No way.

An acorn nut would imply a ground rod. I did not take the class this is strictly hearsay yet I truly believe what he told me and I need to get the die for my hypress asap. He said he did a 3 point fop test. I will give you his phone # if you want. Understand that there is BOTH a ground rod and a heavy pole base in earth contact so win win in my opinion.

 

[tom baker]

If you are concerned about lightning being induced into the building wiring from your big ground grid then TVSS is required.

 

[boboelectric]

I've seen pine trees next to 25' al street lights (with ground rods)get blasted by lightning,luminaire fine.

 

[iaov]

Lightning does some goofy stuff. I believe it is always following the laws of physics bu lots of times it is not obvious how. Hitting a small tree next to a tall well grounded building or pole. Not hitting ships at sea. Its wierd stuff!!:smile:

 

[George Stolz]

Which in itself may or may not increase or decrease the chanses of being hit by lightning in the first place.
Any thoughts on the subject??

Grounding doesn't decrease the odds of getting hit by lightning, it's just a highway for the lightning if it does strike.

 

[quogueelectric]

Grounding doesn't decrease the odds of getting hit by lightning, it's just a highway for the lightning if it does strike.

So why tie the premise wiring to the ground rods which will intentionally diverting the lightning into the building is what I am questioning???

 

[quogueelectric]

If you are concerned about lightning being induced into the building wiring from your big ground grid then TVSS is required.

It is not my building, I am just following the blueprints. I am an installer not an engineer.

 

[benaround]

While wiring some parking lot pole lights a thought crossed my feeble little mind.
The pole mfg had 2 tapped holes of different sizes on thier little ground flange inside the handhole. Why 2 holes??
QUOTE]

one for wire from rod, one for pigtail to EGCs