grounding electrodes

[Ben Trueblood]

I have been told by inspectors in residential situations that if we ground the rebar in the slab that ground rods are not required. I thought that the code required any available electrode to be installed if available. Thoughts?

 

[Speedskater]

I think that is this case "available" means present and accessible rather than possible or purchasable.

 

[don_resqcapt19]

And that applies to all occupancies...not just residential.

 

[erickench]

Ground rods are usually a supplement to a water pipe that's used as a grounding electrode.

 

[Dennis Alwon]

I have been told by inspectors in residential situations that if we ground the rebar in the slab that ground rods are not required. I thought that the code required any available electrode to be installed if available. Thoughts?

Your inspector is correct. Look at art. 250.53(D)(2). It basically states that we must augment the underground water pipe with any of the electrodes in 250.52(A)(2) thru A(8).

If there is no ug water pipe art. 250.56 directs us back to 250.52(A)(4) thru (A)(8)

 

[hillbilly1]

I just had one of my new construction guys call and said he was turned down for a fire pump install, he did not install or connect to a grounding electrode for the fire pump service. (he should have known better anyway, he has a masters license, and of course the engineer that drawed the blueprints didn't know any better either, because he left it off) When he asked the inspector if the exsisting cold water and building steel (commercial building)was Ok, the inspector said he wanted a ground rod too. I told him to politely ask the inspector where in the code he was required to also drive a ground rod when the other two grounding electrodes were present.

 

[augie47]

In this area some POCOs require a ground rod regardless.
Something you might keep in mind.

 

[hillbilly1]

The inspector stuttered when he said it, so I figured he was not sure and defaulted back to one of those "that's the way it's always been done around here."

 

[hillbilly1]

In this area some POCOs require a ground rod regardless.
Something you might keep in mind.

I don't know what part of Tennessee your in, but I wired a house down in Bradley county, Tennesee, back before the Olympics. The Poco was Volunteer Electric if I remember correctly, They required a conduit with no more than two 90's for underground services with a pull string. They supplied and pulled the wire though. First time I had to do that for a Poco. The inspector there was the best I have ever run across, I asked the counter guy at the supply house how inspections were, and he said that the inspector turns everybody down, so I knew kinda of what to expect. I put it in exactly by code as I always do. Passed every inspection. The inspector was well versed in code and did not make up his own personal code as some do. He went through everything methodically. I don't know if he is still inspecting there, but I was impressed with his professionalism.

 

[eprice]

I just had one of my new construction guys call and said he was turned down for a fire pump install, he did not install or connect to a grounding electrode for the fire pump service. (he should have known better anyway, he has a masters license, and of course the engineer that drawed the blueprints didn't know any better either, because he left it off) When he asked the inspector if the exsisting cold water and building steel (commercial building)was Ok, the inspector said he wanted a ground rod too. I told him to politely ask the inspector where in the code he was required to also drive a ground rod when the other two grounding electrodes were present.

In the 2008 code, I believe the code reference might be 250.52(A)(2) and 250.53(D)(2)

250.52(A)(2) tells us that the building steel only counts as a grounding electrode if it is connected to ground by one of the four methods. Note that a metal water line is not one of the four methods. It may be that the building steel did not qualify as a grounding electrode.

250.53(D)(2) requires a supplemental electrode for the water line.

If the building steel does not qualify as discussed above, then the inspector may have considered the rod to be the supplemental electrode, or he may have wanted it to satisfy 250.52(A)(2)(3) so that the building steel could qualify as a grounding electrode. But in either case, he should have been asking for 250.56 compliance as well.

The inspector stuttered when he said it, so I figured he was not sure and defaulted back to one of those "that's the way it's always been done around here."

I might stutter a bit when asked the same question because the thought would be running through my mind "Does that building steel actually qualify as a grounding electrode in this case?"

 

[hillbilly1]

In the 2008 code, I believe the code reference might be 250.52(A)(2)

250.52(A)(2)
"

250.52(A)(2) Was changed in the 2008 code to require building steel connection to the reinforcing bars of a concrete encased electrode if used as such, so you are correct there. This being a Walmart, who is way ahead of everybody using Uffer grounds for many years would easily qualify. Maybe this inspector never inspected a Walmart before, so I will give him the benefit of a doubt.

 

[Ben Trueblood]

In this case the water pipe is not an available electrode. So if I understand it correctly since the water pipe is not available a rod must be driven?

 

[Dennis Alwon]

In this case the water pipe is not an available electrode. So if I understand it correctly since the water pipe is not available a rod must be driven?

Well, that is one way to satisfy code. The other is to use a CEE- rebar electrode- in that cas no rods are needed. There are also other means but generally these are the most common.

Even if the water pipe was an electrode you still would need to supplement the electrode with rods, CEE, or one of the other methods.