Ground Rod Question....

[Gerry347]

Are you allowed to install a 8' ground rod through a hole in a concrete slab instead of putting it outside the building?? I'd leave the top of the rod flush with floor so I can attach the ground wire to it. I have no problem putting the rod outside if I need to but I figured this would accomplish the same thing.

Here is a picture of what I'm talking about.



Thanks

 

[wyliesdiesels]

Nothing prohibiting indoor use however, u need 2 rods...

 

[mrobins297aaa]

why 2 rods?......I'm still trying to get the first one done

 

[wyliesdiesels]

Code mandates 2 rods unless u can prove that there is 25ohms or less of resistance to earth.

The equipment to do so is expensive so most just elect to pound a second rod...

 

[Bighead38]

2 rods might be a regional law or a newer law. Most houses I've seen around here only have one.

 

[Norcal]

2 rods might be a regional law or a newer law. Most houses I've seen around here only have one.

It's been in the NEC for a number of editions, so it's neither, they are choosing to not enforce it.

 

[MushCreek]

In our area, the power company tells you what you need for ground rods. In our case, they want two, a minimum of 8' apart. They recommended putting the second one leading away from the building. You have to have a continuous ground wire from the box and connecting the two rods.

 

[mm08822]

Are you allowed to install a 8' ground rod through a hole in a concrete slab instead of putting it outside the building?? I'd leave the top of the rod flush with floor so I can attach the ground wire to it. I have no problem putting the rod outside if I need to but I figured this would accomplish the same thing.

Typically, 8’ ground rods need to be 8’ in the ground (250.53(G))– meaning at least covered a few inches with soil. Depends upon your AHJ’s opinion. Since you are trying to put a rod through a small hole in the concrete floor and don’t have room to get a connector on the rod below the slab, in the fill, an 8’er could fail or you need a 10’ rod to get the 8’ minimum with clamp exposed above slab.
If you have no other forms of grounding electrode present, such as metal underground water pipe (10’+), concrete encased electrode, etc., etc., then you with need the 2nd rod as a supplemental electrode. (250.53(A)(2))

Since plastic has taken over our world, most grounding electrode systems consist of 2 rods due to its simplicity, cost and ease of inspection.

Here is a picture of what I'm talking about.



Thanks

Nothing prohibiting indoor use however, u need 2 rods...

why 2 rods?......I'm still trying to get the first one done

What year was your current service installed?

Code mandates 2 rods unless u can prove that there is 25ohms or less of resistance to earth.

Actually, it looks like a supplemental electrode is only needed if the primary electrode system is a single rod, pipe, or plate. E.g. – a ufer would not require a supplemental rod.

The equipment to do so is expensive so most just elect to pound a second rod...

And the AHJ typically wants proof of current equipment calibration that may only last 1 year – so more ongoing cost for equipment after initial purchase. $26 for 2 rods – very simple!

2 rods might be a regional law or a newer law. Most houses I've seen around here only have one.

Depends on installation date (NEC edition in force at the time) of service or choice of primary electrode system chosen. A supplemental may not be required or what you are seeing is the supplemental method.

It's been in the NEC for a number of editions, so it's neither, they are choosing to not enforce it.

In our area, the power company tells you what you need for ground rods. In our case, they want two, a minimum of 8' apart. They recommended putting the second one leading away from the building. You have to have a continuous ground wire from the box and connecting the two rods.

That’s really overstepping their jurisdiction – it should just require meeting current NEC.
My local POCO states:
“The customer shall install the service entrance so that all of the grounding/bonding requirements of the NEC are met or exceeded. The customer’s service entrance shall have a minimum of two driven ground rods (8 feet minimum length) at least six (6) feet apart. The grounding electrode conductor shall be continuous from the service entrance main disconnect to both driven ground rods.”

 

[Gerry347]

I knew about the about doing 2 rods but I too thought it was a regional code/law because my house only has one rod and it was built in 2000. I have no issue doing a second rod if it's needed.

Is there a wire size requirement for the ground wire?? The guy at HD said I could use #8 wire for a 60 amp service but I thought if would be #6.

Thanks!!

 

[mm08822]

what size is the service to the building?

 

[TractorJeff]

Quote "Is there a wire size requirement for the ground wire?? The guy at HD said I could use #8 wire for a 60 amp service but I thought if would be #6."

I would guess it is a 60 Amp Service?

 

[pattenp]

NEC only requires the GEC to be continuous from the panel to the first rod. When adding an auxiliary rod (2nd rod) you can use a second piece of GEC connected to the first rod to connect the second rod. However, if using two rods from the start you may as well use one continuous GEC to the end.

 

[mm08822]

NEC only requires the GEC to be continuous from the panel to the first rod. When adding an auxiliary rod (2nd rod) you can use a second piece of GEC connected to the first rod to connect the second rod. However, if using two rods from the start you may as well use one continuous GEC to the end.

You're right, even my POCO has conveniently made their own NEC interpretation in several areas of the text I pasted in from their Service Req's book. They should have stopped with meet/exceed current NEC.

 

[mm08822]

Quote "Is there a wire size requirement for the ground wire?? The guy at HD said I could use #8 wire for a 60 amp service but I thought if would be #6."

I would guess it is a 60 Amp Service?

Guess so too. 15" screen easier to read than 4"!

#8 Cu is min for #2 (or smaller) Cu service conductors. I would do at least #6 for more durability. Just closely follow building contour and secure frequently.

 

[Gerry347]

I think I have all the info I need to get the new panel installed in the barn. I'll post pictures when I'm done so ya'll can make sure I didn't mess something up .

Thanks to everyone for all your help and for answering all my questions. It's folks like you that make this place so great .

 

[wyliesdiesels]

Keep in mind that if u use a #8 for the GEC it needs to be sleeved in conduit. #6 can be ran without conduit as long as its not subject to damage...

 

[Junkman]

I have 4 ground rods because of a strange set of circumstances when we built in 1983, and then remodeled in 1992. When we moved the meter, the electric company wanted it to be connected to the well pipe also.

 

[Gerry347]

Keep in mind that if u use a #8 for the GEC it needs to be sleeved in conduit. #6 can be ran without conduit as long as its not subject to damage...

I'm going with #6 because I don't like the idea of using #8 .

I got lucky with the grounding rods and both were done in about 20 min. I used a little water in each hole and worked the rods up and down by hand until I had about 18" or so left. I finished the the rest with the sledge hammer.

 

[mrobins297aaa]

What year was your current service installed?



And the AHJ typically wants proof of current equipment calibration that may only last 1 year – so more ongoing cost for equipment after initial purchase. $26 for 2 rods – very simple!



Depends on installation date (NEC edition in force at the time) of service or choice of primary electrode system chosen. A supplemental may not be required or what you are seeing is the supplemental method.





That’s really overstepping their jurisdiction – it should just require meeting current NEC.
My local POCO states:
“The customer shall install the service entrance so that all of the grounding/bonding requirements of the NEC are met or exceeded. The customer’s service entrance shall have a minimum of two driven ground rods (8 feet minimum length) at least six (6) feet apart. The grounding electrode conductor shall be continuous from the service entrance main disconnect to both driven ground rods.”

my house was built in the year 2000, I believe I have one ground rod at the house (200 amp service) I'm working on getting one installed at my 100 amp panel in my barn. Are you saying I should have 2 ground rods at the house and 2 more at my barn? (built in 2010 inspected and approved with no ground rod)
why are they needed? because the nec requires it is not a acceptable answer.
whats the purpose of them?

 

[Cmreschke]

Lightning protection. And... the NEC requires them.

 

[mm08822]

my house was built in the year 2000, I believe I have one ground rod at the house (200 amp service) I'm working on getting one installed at my 100 amp panel in my barn. Are you saying I should have 2 ground rods at the house and 2 more at my barn? (built in 2010 inspected and approved with no ground rod)
why are they needed? because the nec requires it is not a acceptable answer.
whats the purpose of them?

(Someone correct me on my timeline if dates are wrong – I regrettably threw out too many old code books.)

So your house was probably built under the 1999 NEC Code. At that time IIRC, there was a requirement for only 1 driven electrode if you didn’t use other methods as your primary electrode. Before then, connecting to the city water supply and jumpering around the water meter was thought to be good enough - steel pipes in contact with earth and water also as a long conductor.
Since water delivery systems were transitioning to plastic tubing and/or random plastic fittings, the reliability of using that method was greatly compromised as no one could be sure where the steel pipe ended and continuity broken underground.

Somewhere early 2000’s code cycle(?), the supplemental rod was added into code as some locations were finding out that ground resistance was very high and the single rod was not good enough. Even proving acceptable today at this very minute, you could have less than 25 ohms to ground doesn’t mean that it is true all year round.

Your house service is grandfathered into the requirements of the then current code cycle enforced at that time.

If you are now putting a new service/subpanel in your garage, it needs to meet today’s 2014 nec requirements (or what cycle your area is under currently). Unless you have a ufer (there are other methods but not too common for residential) you need the 2 driven ground rods at the garage.
If you want to add a 2nd rod the house, it can only help. Your choice. No code issue if you don’t.

As for the why:
refer to wylie’s link in his sticky and these other sites I found:
http://www.ecmag.com/section/codes-standards/grounding-electrode-conductors-building
http://www.esgroundingsolutions.com/different-types-of-grounding-electrodes/
http://ecmweb.com/bonding-amp-grounding/dont-be-neutral-about-grounding
and you can google mike holt on this topic as well.

Regardless of your belief in these ground method requirements, it is considered a necessary practice and I’m sure state legislation adopted the NEC as requirements for your area. So to be code compliant, just do it. $50 for 2 rods, clamps, staples and a few feet of copper is a small price to pay for possibly saving equipment one day down the road. And if it does save your equipment, you will probably never know it and just go on oblivious to that fact.

 

[mrobins297aaa]

(Someone correct me on my timeline if dates are wrong – I regrettably threw out too many old code books.)

So your house was probably built under the 1999 NEC Code. At that time IIRC, there was a requirement for only 1 driven electrode if you didn’t use other methods as your primary electrode. Before then, connecting to the city water supply and jumpering around the water meter was thought to be good enough - steel pipes in contact with earth and water also as a long conductor.
Since water delivery systems were transitioning to plastic tubing and/or random plastic fittings, the reliability of using that method was greatly compromised as no one could be sure where the steel pipe ended and continuity broken underground.

Somewhere early 2000’s code cycle(?), the supplemental rod was added into code as some locations were finding out that ground resistance was very high and the single rod was not good enough. Even proving acceptable today at this very minute, you could have less than 25 ohms to ground doesn’t mean that it is true all year round.

Your house service is grandfathered into the requirements of the then current code cycle enforced at that time.

If you are now putting a new service/subpanel in your garage, it needs to meet today’s 2014 nec requirements (or what cycle your area is under currently). Unless you have a ufer (there are other methods but not too common for residential) you need the 2 driven ground rods at the garage.
If you want to add a 2nd rod the house, it can only help. Your choice. No code issue if you don’t.

As for the why:
refer to wylie’s link in his sticky and these other sites I found:
http://www.ecmag.com/section/codes-standards/grounding-electrode-conductors-building
http://www.esgroundingsolutions.com/different-types-of-grounding-electrodes/
http://ecmweb.com/bonding-amp-grounding/dont-be-neutral-about-grounding
and you can google mike holt on this topic as well.

Regardless of your belief in these ground method requirements, it is considered a necessary practice and I’m sure state legislation adopted the NEC as requirements for your area. So to be code compliant, just do it. $50 for 2 rods, clamps, staples and a few feet of copper is a small price to pay for possibly saving equipment one day down the road. And if it does save your equipment, you will probably never know it and just go on oblivious to that fact.

Yeah your probably right it's only $50, thanks for taking the time to explain it.

 

[Gerry347]

Regardless of your belief in these ground method requirements, it is considered a necessary practice and I’m sure state legislation adopted the NEC as requirements for your area. So to be code compliant, just do it. $50 for 2 rods, clamps, staples and a few feet of copper is a small price to pay for possibly saving equipment one day down the road. And if it does save your equipment, you will probably never know it and just go on oblivious to that fact.

That's why I did it p.

 

[Showkey]

Not saying it meets code or is right or wrong also Not looking for an argument or agreement ........but..........this is the norm in new construction in the local area. Single wire single ground rod to the footing. Brand new install with in the last week. Not sure what they are doing back at the transformer box as far as grounds if anything. What you see it what is done and is very very common.

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[mike93lx]

Single wire single ground rod to the footing. Brand new install with in the last week.

that's fine and it's not a ground rod, just wire connected to the metal within the foundation. it's called a UFER