Residential Grounding

[Npstewart]

Is one 8' driven ground rod sufficient to meet the grounding requirements at the main service in the per the NEC or is at minimum the building steel also required? I understand that 25 ohms to ground minimum is required.

 

[Dennis Alwon]

Is one 8' driven ground rod sufficient to meet the grounding requirements at the main service in the per the NEC or is at minimum the building steel also required? I understand that 25 ohms to ground minimum is required.

One ground rod is sufficient if you can proof 25 ohms but in general it is easier to drive 2 rods. If you have a CEE then you do not need the rods. The building steel is also req. to be bonded.

 

[Npstewart]

CEE?

 

[Dennis Alwon]

CEE?

Concrete encased electrode--#4 in the footers.

 

[infinity]

If the building has structural steel construction then it would need to utilize a CEE. Also if the steel qualifies as an electrode that must be used also. In either case you can forget the ground rods.

 

[Npstewart]

This is residential, its all block & and wood.

 

[infinity]

Ok so is not a strucutral steel building? Your OP mentioned building steel. Can you describe in detail what you have? Different methods can have differenet answers.

Is one 8' driven ground rod sufficient to meet the grounding requirements at the main service in the per the NEC or is at minimum the building steel also required? I understand that 25 ohms to ground minimum is required.

 

[Npstewart]

Basically its just a 200A service in a residential project. The construction down here in Florida for most houses is CMU block. There is re-bar within the block and steel in the foundation. Basically an electrician only drove 1 ground rod and im trying to see if that is sufficient or if it needs to be bonded to something else or at least install a 1 more ground rod.

 

[tom baker]

Basically its just a 200A service in a residential project. The construction down here in Florida for most houses is CMU block. There is re-bar within the block and steel in the foundation. Basically an electrician only drove 1 ground rod and im trying to see if that is sufficient or if it needs to be bonded to something else or at least install a 1 more ground rod.

if you have rebar in a footer that meets the requirements of 250.52(A)(3) then it has to be used for the GES. No supplemental ground rods are required.

 

[Npstewart]

Ok, so you couldnt use the rods in lieu of the building steel? For example, you couldnt just provide a rod complying with250.52 (5) instead of bonding it to the steel?

 

[RICK NAPIER]

No substitutions.

 

[haskindm]

All grounding electrodes that meet the definition of a grounding electrode in article 250 that are "PRESENT" must be used as part of the grounding electrode system. Period. We do not have a choice of which electrode(s) to use, any of them that are there MUST be used. If there is a concrete encased electrode present and the electrician decided to use a ground rod (or even two ground rods) instead, that is wrong. The concrete encased electrode, if present, must be used. If there is also grounded building steel, it must also be used. If there is an underground water pipe that meets the definition of a grounding electrode it must also be used.

 

[Dennis Alwon]

I think we may be talking about similar stuff. We must not use the term building steel if you are talking about rebar(steel) in the footings. That is not considered building steel. If you have rebar in the footers and a #4 copper conductor was installed and used as a CEE then no rods are necessary.

In many areas you must use the rebar if it exists unless it is an existing structure. NC has an amendment, which I wish they would change, to exempt using the rebar. In that case 2 rods are driven.

 

[infinity]

When speaking of structural steel buildings we mean something like this:

 

[Npstewart]

I really appreciate everyone's help with this! Thanks!