Grounding electrode for separate building

[romeo]

I attended a code class yesterday to fulfill my6 HR.requirement for Ma.

The subject of a grounding electrode system for a building supplied by a feeder using a ground rod or rods came up. It was assumed that 0ne rod did not meet the 25 ohm rule.

The instructor told the class that only one rod was required. I disagreed, and stated that the grounding electrode system was required by section 250.32 and that it also required that it be in accordance with Part III of articale 250.

Section 250.56 found in chapter III requires that a single electrode of a rod that does not have a resistance to ground of 25 ohms or less shall be augmented by one additional electrode, in this case being a ground rod.

He said we would get back to the question later but that never happened.

Please give me your opinion.

Thanks

 

[augie47]

You are correct.
In most cases, the separate building IS required to have a grounding electrode system per Part III of 250 just as the main structure. If a rod electrode is needed it would require a second rod if the 1st did not have a resistance of 25 ohms or less.

 

[dicklaxt]

Does it matter if it is an adjacent bonded rod or an extended original?

 

[Volta]

Does it matter if it is an adjacent bonded rod or an extended original?

I don't think so, if I understand your question. It does need to be at least 6' away 250.56. Ideally, the additional rod(s) will be as far away as they are long. Good practice, but not required.

 

[suemarkp]

I think you could argue that the rods at the primary building are the supplemental required rod. But you'd have to have a #6 EGC in the feeder to the building so that it qualified as a bonding jumper to the supplemental rod. If the EGC is smaller than #6, I don't see how you can comply without measuring the resistance of the rod.

 

[romeo]

Grounding electrode for separate building

I think you could argue that the rods at the primary building are the supplemental required rod. But you'd have to have a #6 EGC in the feeder to the building so that it qualified as a bonding jumper to the supplemental rod. If the EGC is smaller than #6, I don't see how you can comply without measuring the resistance of the rod.

If that would apply, then the EGC could serve a GEC and the GES in the primary building could serve the separate building.

Just my opinion

 

[mcclary's electrical]

If that would apply, then the EGC could serve a GEC and the GES in the primary building could serve the separate building.

Just my opinion

Believe me,,,that's been argued here before

 

[romeo]

grounding electrode for separate building

grounding electrode for separate building

What was the outcome of the last argument?

 

[Pierre C Belarge]

What was the outcome of the last argument?

hehehehe...do you really want to subject yourself to the pain?

 

[Dennis Alwon]

Let's look at article 250.32(B). From a logical standpoint I do not see why an egc cannot be both an egc and a gec. However the article below does not states what the egc can be used for and it does not include an egc.

250.32(B) Grounded Systems. For a grounded system at the separate building or structure, an equipment grounding conductor as described in 250.118 shall be run with the supply conductors and be connected to the building or structure disconnecting means and to the grounding electrode(s). The equipment grounding conductor shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded. The equipment grounding conductor shall be sized in accordance with 250.122. Any installed grounded conductor shall not be connected to the equipment grounding conductor or to the grounding electrode(s).

This is another possible bite in the butt. Not sure how this can be enforced if the rods are not present. Just a thought.

250.30(A)(7) Grounding Electrode. The grounding electrode shall be as near as practicable to and preferably in the same area as the grounding electrode conductor connection to the system. The grounding electrode shall be the nearest one of the following:
(1) Metal water pipe grounding electrode as specified in 250.52(A)(1)
(2) Structural metal grounding electrode as specified in 250.52(A)(2)
Exception No. 1: Any of the other electrodes identified in 250.52(A) shall be used where the electrodes specified by 250.30(A)(7) are not available.
Exception No. 2 to (1) and (2): Where a separately derived system originates in listed equipment suitable for use as service equipment, the grounding electrode used for the service or feeder equipment shall be permitted as the grounding electrode for the separately derived system.

 

[Pierre C Belarge]

Dennis
250.30 is for separately derived systems, not separate structures.

 

[Dennis Alwon]

Dennis
250.30 is for separately derived systems, not separate structures.

Hey Pierre good to see you back.

Thanks for the check on that. I thought I read this somewhere but when I saw it I paid no never mind to what it applied to. What about the other section????

 

[Pierre C Belarge]

Thanks Dennis, it is good to be back.

I do not have an issue with the other Section you provided.