Which grounding electrodes are required?

tx2step

Senior Member
We're currently under the 2002 code, but will be moving to the 2014 before long.

250.50 requires the first 6 types of electrodes [250.52(A)(1) thru (A)(6)] to be used "If available on the premises..."

Of the first 3 types:
1. UG water pipe:
(a) This appears to me to be a required electrode, if it exists...right? You can't choose not to use it?
(b) It must be supplemented by at lease one additional type of electrode, right? 250.53(D)(2)?

2. metal building frame:
(a) This appears to me to be a required electrode, if it exists...right? You can't choose not to use it?
(b) Does this have to be supplemented by any other electrode? Or is it sufficient alone?
(b) Do you ever have to test it to see if it's really working? If so, how do you usually have to test it? What would be an acceptable resistance?

3. concrete-encased electrode:
(a) For new construction with rebar in the foundation/footings, is this a "required" electrode? Or can you choose not to have a concrete-encased electrode, even if the new footings would qualify as one if they are connected?
(b) If it's used, does it have to be supplemented by any other electrode? Is it sufficient alone?
(c) Do you ever have to test it to see if it's really working? If so, how do you usually have to test it? What would be an acceptable resistance?

For ground rods (250.56) do you always just install a second one at lease 6' apart? Of do you usually demonstrate that a single one is under 25 ohms?

I want to see how the grounding electrode requirements are generally interpreted/implemented in other parts of the country.

Thanks!!!
 

edward

Senior Member
We're currently under the 2002 code, but will be moving to the 2014 before long.

250.50 requires the first 6 types of electrodes [250.52(A)(1) thru (A)(6)] to be used "If available on the premises..."

Of the first 3 types:
1. UG water pipe:
(a) This appears to me to be a required electrode, if it exists...right? You can't choose not to use it? CORRECT
(b) It must be supplemented by at lease one additional type of electrode, right? 250.53(D)(2)? CORRECT

2. metal building frame:
(a) This appears to me to be a required electrode, if it exists...right? You can't choose not to use it? CORRECT
(b) Does this have to be supplemented by any other electrode? Or is it sufficient alone? No supplement is required
(b) Do you ever have to test it to see if it's really working? If so, how do you usually have to test it? What would be an acceptable resistance? No testing is required per NEC

3. concrete-encased electrode:
(a) For new construction with rebar in the foundation/footings, is this a "required" electrode? Or can you choose not to have a concrete-encased electrode, even if the new footings would qualify as one if they are connected? REQUIRED
(b) If it's used, does it have to be supplemented by any other electrode? Is it sufficient alone? No supplement is required
(c) Do you ever have to test it to see if it's really working? If so, how do you usually have to test it? What would be an acceptable resistance? Testing is not required per NEC

For ground rods (250.56) do you always just install a second one at lease 6' apart? Of do you usually demonstrate that a single one is under 25 ohms? Just install the 2nd one if requested by the AHJ

I want to see how the grounding electrode requirements are generally interpreted/implemented in other parts of the country. Some of my local AHJ do not require the 2nd grounding rod. They have done extensive testing and the soil's resistivity is low enough.

Thanks!!!
See red comments
 

petersonra

Senior Member
This is the deal.

You have to use ALL of the GE that are present, although if there are more than one CEE present you only have to bond to one of them.

Sometimes what might appear to be a GE isn't because it does not meet the requirements of the code for that type of GE.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
It is subject to interpretation.

Usually the circuit that will energize it can bond it at the same time.

But again, it is subject to interpretation and will depend on AHJ.
Under the rules of the NEC, no special bonding is required for the gas piping. If there is CSST gas piping then fuel gas code and the manufacturer's instructions require additional bonding, but the NEC does not.
 

tx2step

Senior Member
For concrete encased electrodes (or any other electrodes) does any AHJ ever test the electrode to see what the resistance to ground actually measures, to determine how effective it really is?

If they do sometimes test them, do they use one of the clamp-on ground testers or do they use the fall-of-potential test method?
 
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