Ground Rod at seperate structure

[mikehughes8]

According to 250.32 if I have a feeder going to a seperate building I must install an electrode or electrode system. Then IAW 250.56 I must meet the 25ohm requirement or drive another rod no less than 6 feet away from the first.

Now here's the question:

If I was determined not to drive that second ground rod and decided to use a Ground Resistance Tester to prove 25ohms or less do I have to disconnect the ground rod under test from the rest of the system or can I leave it connected? I ask because by virtue of the EGC I am actually connected to a larger grounding electrode system. So I may get 25ohms or less while connected but exceed 25ohms if not.

 

[resistance]

f I was determined not to drive that second ground rod and decided to use a Ground Resistance Tester to prove 25ohms or less do I have to disconnect the ground rod under test from the rest of the system or can I leave it connected? I ask because by virtue of the EGC I am actually connected to a larger grounding electrode system. So I may get 25ohms or less while connected but exceed 25ohms if not.

I say yes you would have to disconnect it---seeing that 250.56 says: A single electrode.......

 

[Jim W in Tampa]

Why do so many fight that second rod ? Will you do test while inspector is there ?

 

[mikehughes8]

Why do so many fight that second rod ? Will you do test while inspector is there ?

I am simply trying to intepret what the NEC is saying. I always drive a second rod and forget about it. However, others when trying to validate their installation do it by taking a ground resistance reading while the electrode is in system. Does the code allow this or not? I cannot make that determination from the language. The code seems to leave some room on this.

 

[resistance]

Why do so many fight that second rod ? Will you do test while inspector is there ?

LOL!! When we have work , it's definitely a fight around here. We live on a bunch of mountain rocks. when I first bought my home, our backyard had enough rocks to build a small bridge!!

 

[resistance]

I am simply trying to intepret what the NEC is saying. I always drive a second rod and forget about it. However, others when trying to validate their installation do it by taking a ground resistance reading while the electrode is in system. Does the code allow this or not? I cannot make that determination from the language. The code seems to leave some room on this.

I don't think it leaves room for further interpretation. "You are testing the resistance of a single rod, not the entire system." Yet, I'm open to hear other opinions!

 

[mikehughes8]

Let me add that I am the one doing the inspecting...but not in the States. I am in Afghanistan. The soil out here is less than ideal and I know that no single rod will give you 25ohms or less. The contractor in question can produce ground reading showing 25ohms or less but this is only when the electrode in question is connected to the larger GEC system. Hence the reason why I ask the question.

 

[mikehughes8]

I don't think it leaves room for further interpretation. "You are testing the resistance of a single rod, not the entire system." Yet, I'm open to hear other opinions!

I tend to agree with you but I lack certainty.

 

[Hutch708]

The instructions with the tester that I carry in my inspection vehicle requires the test be done with nothing connected to the ground rod except the testing equipment.

 

[mikehughes8]

The instructions with the tester that I carry in my inspection vehicle requires the test be done with nothing connected to the ground rod except the testing equipment.

Fall-Off-Potential ground testing can be done on ground mats or ground grids without having to isolate each individual rod.

 

[resistance]

Let me add that I am the one doing the inspecting...but not in the States. I am in Afghanistan. The soil out here is less than ideal and I know that no single rod will give you 25ohms or less. The contractor in question can produce ground reading showing 25ohms or less but this is only when the electrode in question is connected to the larger GEC system. Hence the reason why I ask the question.

Wow! You are in Afghan? Maybe I need to gear-up and go!!! Our business is suffering! It use to pick-up, then slow down---leaving some room for optimism-- but now it's ridiculous! I haven't received one call this week . My generals aren't receiving any work, so this has effected a percentage of my cash flow. We normally survive off referrals (90% of our business). But, now that more people are loosing their jobs--it seems every avenue to achieve business has closed, or not effective! Unfortunately, we had to cancel one source of advertising, because it's no longer justified.

Yeah, I have to make this business work, or my family is doomed! I find it amazing..nothing, I'll keep it to myself!

Happy to hear you have work overseas!!!

Sorry for getting off topic. It just seems all this hard work means nothing!!! All the studing, licensing, etc etc!! :roll:

 

[M. D.]

I doubt the second rod will do much ,.. other than comply that is...

Stay safe ,.. and thank you!

 

[tom baker]

Right. When you test more than one GR, you are getting the combined resistance of all in parallel.

 

[mikehughes8]

Wow! You are in Afghan? Maybe I need to gear-up and go!!! Our business is suffering! It use to pick-up, then slow down---leaving some room for optimism-- but now it's ridiculous! I haven't received one call this week . My generals aren't receiving any work, so this has effected a percentage of my cash flow. We normally survive off referrals (90% of our business). But, now that more people are loosing their jobs--it seems every avenue to achieve business has closed, or not effective! Unfortunately, we had to cancel one source of advertising, because it's no longer justified.

Yeah, I have to make this business work, or my family is doomed! I find it amazing..nothing, I'll keep it to myself!

Happy to hear you have work overseas!!!

Sorry for getting off topic. It just seems all this hard work means nothing!!! All the studing, licensing, etc etc!! :roll:

Well I am in the military so I don't work for a contractor. I represent the government in making sure the contractors are in compliance with code. We could sure use some well qualified electricians over here.
There are 3 primary electrical contractors here now: Inglett and Stubbs, Flour, and KBR.
I am sorry to hear about the your work situation. If you would ever consider coming into theatre (it is not as bad as the news would have you think) I am sure one of the above contractors would hire you on. God knows they need help.

 

[Cavie]

I don't think it leaves room for further interpretation. "You are testing the resistance of a single rod, not the entire system." Yet, I'm open to hear other opinions!

My company has a clamparound resistence tester and the instructions state that it is designed to be used on multi grounded systems without disconnecting the individual rod. It works great. Just clamp around and read just like an amprobe.

 

[resistance]

Well I am in the military so I don't work for a contractor. I represent the government in making sure the contractors are in compliance with code. We could sure use some well qualified electricians over here.
There are 3 primary electrical contractors here now: Inglett and Stubbs, Flour, and KBR.
I am sorry to hear about the your work situation. If you would ever consider coming into theatre (it is not as bad as the news would have you think) I am sure one of the above contractors would hire you on. God knows they need help.

Nice to hear you are inspecting the electrical overseas. I've heard horror stories!!! I served during the Golf war, and spent time in UAE, Bahrain, and Somalia.