I am often challenged by contractors when I ask for documentation of ground testing of their grounding system or in today's case, a ground rod. I show up for a final electrical inspection and find the ground rod has been installed however, I have no proof that 3' wasn't cut off (which has happened because there encountered rock), so I always ask for documentation that the ground rod read less than 25ohms. The contractors will state nowhere in the NEC code that it requires that I have to provide documentation or that it requires to be inspected. I have looked through the NEC, and I can not really find anything that requires the grounding to be inspected am I missing something? I can not believe that I should take the word of the contractor that everything is grounded properly. Yes, I can see the visible connections, but that doesn't mean that during construction, the ground conductor wasn't damaged or cut where it ties to the foundation reinforcement, etc. I would think at the end of a commercial project, a final ground test would be required for all equipment and grounding, either rods or whatever. I find the engineer's specifications are usually very vague in describing the testing of the grounded system. Hopefully, someone can provide me with NEC backing that testing is required. Operating under the 2023 NFPA 70.
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Ground Rod 2
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" ...I am often challenged by contractors when I ask for documentation of ground testing of their grounding system..., a ground rod. #1...I have no proof that 3' wasn't cut off (which has happened because there encountered rock)....#2.... I always ask for documentation that the ground rod read less than 25ohms. #3... The contractors will state nowhere in the NEC code that it requires that I have to provide documentation or that it requires to be inspected. I have looked through the NEC, and I can not really find anything that requires the grounding to be inspected am I missing something? ...#4. I can not believe that I should take the word of the contractor that everything is grounded properly. ....#5... I can see the visible connections, but that doesn't mean that during construction, the ground conductor wasn't damaged or cut where it ties to the foundation reinforcement, etc....#6. ...I would think at the end of a commercial project, a final ground test would be required for all equipment and grounding, .. I find the engineer's specifications are usually very vague in describing the testing of the grounded system. Hopefully, someone can provide me with NEC backing that testing is required. Operating under the 2023 NFPA 70."
I have my personnel opinion for your consideration. It involves the scope of work in the tender document signed, which would be the legal standing for both parties.
1. As you have no proof, it is better not to raise the issue. Ref NEC Art 250.52 (A) (5), 250.53 (A) (1), 250.53 (A) (4).
2. The contractor should submit document proof that the single rod is < 25ohm. Ref 250.53 (A) (2) exception.
3. NEC is not intended as a design specification or as an instruction manual, nor as a tender document (author). Ref Art 90.2 (A)
4. You should NOT take the words without any legal documentation.
5. It is your responsibility to ensure the works are acceptable before signing off.
6. Check the scope of work in the tender document. What is not covered in the NEC may have to refer to other standards , see IEEE 80, 81,142 1100, NFPA 780 etc.
Che Kuan Yau (Singapore)
I have my personnel opinion for your consideration. It involves the scope of work in the tender document signed, which would be the legal standing for both parties.
1. As you have no proof, it is better not to raise the issue. Ref NEC Art 250.52 (A) (5), 250.53 (A) (1), 250.53 (A) (4).
2. The contractor should submit document proof that the single rod is < 25ohm. Ref 250.53 (A) (2) exception.
3. NEC is not intended as a design specification or as an instruction manual, nor as a tender document (author). Ref Art 90.2 (A)
4. You should NOT take the words without any legal documentation.
5. It is your responsibility to ensure the works are acceptable before signing off.
6. Check the scope of work in the tender document. What is not covered in the NEC may have to refer to other standards , see IEEE 80, 81,142 1100, NFPA 780 etc.
Che Kuan Yau (Singapore)
- Thread starter
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2
- #4
The easy way to comply with NEC without testing or documentation, is to drive two rods appropriately separated. This will likely satisfy the building inspector. If you you wish to go beyond the NEC, it will need to be in your design documents.
resqcapt19
Electrical
The only time the NEC requires testing of a grounding electrode is the case where you want to use a single rod, pipe, plate electrode.
The main rule says electrodes of those types must be supplemented by another electrode of one of the types in 250.52(A)(2) through (A)(8)
Often the engineering specifications will require a specific resistance for the grounding electrode system and require testing to prove it, but the NEC does not. In reality the connection to earth does not play a very big part in the safety of an electrical system. The bonding that provides the effective ground-fault current path is much more important.
The main rule says electrodes of those types must be supplemented by another electrode of one of the types in 250.52(A)(2) through (A)(8)
Code:
250.53(A)(2) Supplemental Electrode Required. A single rod, pipe, or plate electrode shall be supplemented by an additional electrode of a type specified in 250.52(A)(2) through (A)(8). The supplemental electrode shall be permitted to be bonded to one of the following:
(1)Rod, pipe, or plate electrode
(2)Grounding electrode conductor
(3)Grounded service-entrance conductor
(4)Nonflexible grounded service raceway
(5)Any grounded service enclosure
Exception: If a single rod, pipe, or plate grounding electrode has a resistance to earth of 25 ohms or less, the supplemental electrode shall not be required.]Often the engineering specifications will require a specific resistance for the grounding electrode system and require testing to prove it, but the NEC does not. In reality the connection to earth does not play a very big part in the safety of an electrical system. The bonding that provides the effective ground-fault current path is much more important.
If it's not in the NEC, then write it into the contract specification or add it to the drawing so they have to provide it. Seems simple enough.
-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates
-Dik
Look into an adaptation of TDR equipment.
With an appropriate TDR set you may easily measure the length of the ground rods.
Time Domain Reflectometry.
You may be able to roll your own with a smart phone and a piezoelectric crystal.
It will take someone younger than me to work out the details.
--------------------
Ohm's law
Not just a good idea;
It's the LAW!
With an appropriate TDR set you may easily measure the length of the ground rods.
Time Domain Reflectometry.
You may be able to roll your own with a smart phone and a piezoelectric crystal.
It will take someone younger than me to work out the details.
--------------------
Ohm's law
Not just a good idea;
It's the LAW!
I have the following personal opinion for your consideration.
1. In the old/superseded NEC Art 250.56 , a single electrode ...that does not have a resistance to ground of 25 ohms or less shall be augmented by one additional electrode ...
1.1 In the current NFPA 70 2023 , Art 250.53 (A) (2) a single rod...shall be supplemented by an additional electrode of a type...Exception If a single rod... grounding electrode has a resistance to earth of 25 ohms or less, the supplemental electrode shall not be required
2. The superseded NEC requirement differs from the current, 2023 edition.
2.1 Superseded Code, if an additional/supplemental electrode is installed, no test or document/proof that the resistance is < 25 ohms is required.
2.2 Current 2023 Code would mean that supplemental electrode shall not be required if the single rod is < 25 ohms.
Che Kuan Yau (Singapore)
1. In the old/superseded NEC Art 250.56 , a single electrode ...that does not have a resistance to ground of 25 ohms or less shall be augmented by one additional electrode ...
1.1 In the current NFPA 70 2023 , Art 250.53 (A) (2) a single rod...shall be supplemented by an additional electrode of a type...Exception If a single rod... grounding electrode has a resistance to earth of 25 ohms or less, the supplemental electrode shall not be required
2. The superseded NEC requirement differs from the current, 2023 edition.
2.1 Superseded Code, if an additional/supplemental electrode is installed, no test or document/proof that the resistance is < 25 ohms is required.
2.2 Current 2023 Code would mean that supplemental electrode shall not be required if the single rod is < 25 ohms.
Che Kuan Yau (Singapore)
Palletjack
Electrical
I assume you’re an electrical inspector? If so you should know the NEC. One rod, documentation of <25 ohms. Two rods, nothing required.
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