Ground rod size - where exactly is 5 ft allowed?

[gamp945]

Hi all,

In searching for some information on ground rods I came across a recent article in a trade magazine:

https://iaeimagazine.org/magazine/f...ound-rod-and-its-little-known-use-in-the-nec/

The author of the article points out that the 2017 NEC allows a 5-ft ground rod in certain circumstances.

The article seems to conclude that a 5-ft ground rod is allowed if "the building or structure has no intersystem bonding termination or grounding means".

If I understand this correctly, this simply means that if the building is not served with communications wiring (phone, cable, etc), then it does not have an intersystem bonding terminal. Am I correct? If so, many - perhaps most - outbuildings and garages meet this description and would only require a 5-ft ground rod.

I tried doing some more searching to see if the 5-ft ground rod has been written about elsewhere but did not find anything. The author's article seems to be well researched and he even cites his interaction with the "NEC code making panel" in support of his claims.

What do you all think? Is my reading of this article correct? I'm not an electrician so maybe I've missed something basic in the article. If my understanding is correct, then the use of 5-ft ground rods could save some serious aggravation for some forum members!

One detail that remains unclear to me from the article is if a 5-ft ground rod needs to be measured at 25 ohms resistance (like the 8-ft ground rod language requires) and if a pair of 5-ft ground rods would be required if resistance is not measured (again, like the 8-ft ground rod language requires).

 

[nadogail]

IMHO, This is a question for your local authority having jurisdiction.

In plain language ask your local electrical inspector, rules vary by location.

 

[gamp945]

I agree that you should always ask your local inspector about more nuanced/complicated code issues, but my point in posting this thread is to clarify what the NEC says and how this might apply to people building a detached garage or other outbuilding.

 

[Stuart in MN]

He refers to NEC article 800, which is for communications circuits. The way I read it, you can use a 5 foot ground rod for grounding a communications circuit where there is no other grounding method available, which infers there's no power to that building.

To provide the ground system for the electrical service to a building, I think you still need to go by what it says in article 250-Grounding and Bonding.

 

[dave*99]

He refers to NEC article 800, which is for communications circuits. The way I read it, you can use a 5 foot ground rod for grounding a communications circuit where there is no other grounding method available, which infers there's no power to that building.

To provide the ground system for the electrical service to a building, I think you still need to go by what it says in article 250-Grounding and Bonding.

I agree with Stuart. I believe the chain of code goes something like this:

If you have an electrical service, follow section 250 and install 8ft ground rod(s)
Now that you have a service if you add communications circuits (telephone or CATV) you have to add an inter system bonding connection. This is basically a terminal block where the CATV, Telephone and electric service and ground rod connections all come together.

Section 800 describes the ground rod requirements essentially for the absence of the type of grounding system required for an electric service. So as Stuart pointed out - cases where there is no electric service.

 

[alfredeneuman]

the way i read it, you can use a 5 foot ground rod for grounding a communications circuit where there is no other grounding method available, which infers there's no power to that building.

^^^^^this^^^^^

 

[gamp945]

Thanks for the replies. I agree with your interpretation of the code - a 5-ft ground rod can only be used for buildings without power. I think the author of the article does not understand this because the article is misleading in my opinion.

 

[dave*99]

Thanks for the replies. I agree with your interpretation of the code - a 5-ft ground rod can only be used for buildings without power. I think the author of the article does not understand this because the article is misleading in my opinion.

I agree that the article is poorly written. In fact, a few sentences from this thread do a better job of explaining the story than his entire article.