2nd ground rod alternative

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ammklq143

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Location
Iowa
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Electrician
I have to build an electrical service on a pole that has concrete within a few inches of it. Normally, I just add a 2nd ground rod 6 ft away but in this case that means hammering out their concrete. Other than removing concrete or driving a single ground rod and checking the resistance in hopes of being less then 25 ohms is there another way to do this? I don’t have a ground tester and I’m fairly certain it wouldn’t be less than 25 ohms anyway. Thanks for any help.
 
ammklq143 said:
I have to build an electrical service on a pole that has concrete within a few inches of it. Normally, I just add a 2nd ground rod 6 ft away but in this case that means hammering out their concrete. Other than removing concrete or driving a single ground rod and checking the resistance in hopes of being less then 25 ohms is there another way to do this? I don’t have a ground tester and I’m fairly certain it wouldn’t be less than 25 ohms anyway. Thanks for any help.
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where does it say in the code you have to hammer out the concrete?
 
petersonra said:
where does it say in the code you have to hammer out the concrete?
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Sorry. I didn't explain that the pole is surrounded by concrete so in order to get another ground rod out 6 ft from the pole I would need to hammer out a path to get the wire out to it.
 
petersonra said:
there is no code rule that requires this.
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250.53 states that a supplemental electrode is required unless the resistance to earth is less than 25 ohms. I'm fairly certain I can't get less than 25 ohms resistance with one ground rod so I need to add a supplementary rod a minimum of 6 ft. away. The pole is surrounded by concrete so I would need to remove some to get the second rod installed.
 
ammklq143 said:
250.53 states that a supplemental electrode is required unless the resistance to earth is less than 25 ohms. I'm fairly certain I can't get less than 25 ohms resistance with one ground rod so I need to add a supplementary rod a minimum of 6 ft. away. The pole is surrounded by concrete so I would need to remove some to get the second rod installed.
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I was referring to chipping out the concrete.

you can't just go 6 feet away and drill a hole in the concrete?

there is no requirement that the wire connecting the 2 rods can't be on top of the concrete as long as it is protected.
 
If this is a transmission pole & the transformer is directly above your riser I'd probably talk yo you AHJ on that requirement -- these poles generally have a pretty good grounding system that ties to the transformer grounded conductor - the real reason is to direct induced voltage from lighting strikes to earth & if the power company reasonable feels their grounding system protects their transformer why would you need 2 rods other that NEC forces the action in this particular instance. - you have a remote pole & it would be highly unlikely induce voltage on the service equipment would reach a remote structure disconnect when you would have an earth grounded transformer & an earth grounded service on the same pole within feet of each other.
 
petersonra said:
I was referring to chipping out the concrete.

you can't just go 6 feet away and drill a hole in the concrete?

there is no requirement that the wire connecting the 2 rods can't be on top of the concrete as long as it is protected.
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Who is going to run a raceway on top of the concrete next to a pole? Could even be a sidewalk. :)
 
infinity said:
Who is going to run a raceway on top of the concrete next to a pole? Could even be a sidewalk. :)
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I don't know what he has. If he wants to chip out a sidewalk he will need to get permission from the city that owns the sidewalk.

I kind of got the impression the pole was embedded in the concrete to hold it up.

Whoever owns that concrete is probably going to want to have a say in what he does and how he does it.
 
why can't you just use a hammer drill bit and Roto Hammer and drill through the concrete, then drive your ground rod through the hole? Or drive the second Rod far enough away that it's not in concrete?
 
JFletcher said:
why can't you just use a hammer drill bit and Roto Hammer and drill through the concrete, then drive your ground rod through the hole? Or drive the second Rod far enough away that it's not in concrete?
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It's in a parking lot surrounded by concrete so I either need to get a ground resistance of less than 25 ohms with a single ground rod right next to the pole (probably not) or hammer out concrete and run a ground wire to a second ground rod. I thought about threading 2 rods together so it's a 16 ft. rod as a way to try to get the resistance low enough to pass but with the soil conditions I still don't think that's going to work and the site is 2 hours away so I don't really want to take that chance and have it fail.
 
Well in that case I would rent a concrete saw, cut about a 2 in wide by 4in deep v-notch channel a little over 6 ft, drill a hole through the concrete where the second rod goes, drive it in, put your ground wire between the two, and fill it in with thinset or quick-setting cement. It does not sound like you will be able to run your ground wire between the two above the concrete, even if it were protected with RMC... will probably either be a trip Hazard, or get tore up with vehicle traffic
 
JFletcher said:
Well in that case I would rent a concrete saw, cut about a 2 in wide by 4in deep v-notch channel a little over 6 ft, drill a hole through the concrete where the second rod goes, drive it in, put your ground wire between the two, and fill it in with thinset or quick-setting cement. It does not sound like you will be able to run your ground wire between the two above the concrete, even if it were protected with RMC... will probably either be a trip Hazard, or get tore up with vehicle traffic
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sounds like the best plan but might be best to run this by the people who own the parking lot. personally, I would pay someone who does concrete work for a living to come do it.
 
ammklq143 said:
It's in a parking lot surrounded by concrete so I either need to get a ground resistance of less than 25 ohms with a single ground rod right next to the pole (probably not) or hammer out concrete and run a ground wire to a second ground rod. I thought about threading 2 rods together so it's a 16 ft. rod as a way to try to get the resistance low enough to pass but with the soil conditions I still don't think that's going to work and the site is 2 hours away so I don't really want to take that chance and have it fail.
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You only need a saw cut width wide enough to push a #6 bare solid ground wire below the surface of the top of the concrete. The cut depth would only need to be 3/8" + or so. You could use what ever type of sealant caulk you think will work to hold the wire in place.

As for the hole in the concrete, for the ground rod, I would probably start there first. Just to make sure you will be able to drive the rod down in the location you picked. As for the size of the hole in the concrete you make, as you are aware, it only needs to be big enough to drive the rod below the surface of the concrete and enough room around the rod for you to install the ground wire and tighten the ground rod clamp to the rod.

.
 
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