100 and 200 amp residential and commercial service

[netcom45850]

this question applies to 100 and 200 amp residential and commercial services
where in the code is the number of ground rods specified? I have been taught 1 5/8x8 rod for 100, 2 for 200, 3 for 300. this is in addtion to the water main grounding conductor. Am I right or over doing it? please let me know.

 

[Dennis Alwon]

article 250.56---
rod size art.250.52(A)(5)

You never need more than 2 ground rods

 

[cpal]

250.56 addresses the number of electrodes in somuch as it requies the resistance to be 25 ohms or less.

If you read the language in the nec it only requies one additional electrode.
IMO once you drive the second rod (spaced 6 feet)you are done.

 

[iwire]

I agree with the others but will add you may not be required to provide any ground rods.

If the building has a concrete encased electrode in the footing you will not need any additional electrodes.

 

[infinity]

I'm curious as to where you got the 1,2,3 rod idea from?

 

[AES1005]

Ground rods

Ground rods

Grounding with made electrodes, 250.56 where a single electrode does not have a resistance to ground of 25 ohms or less is augmented by one Additional electrode. With in mind this is for lightning protection and a reference to ground. Service amps would not effect the amount.

 

[netcom45850]

Thanks For The Reply's
I Have Had Jobs That Were State Inspected 300 Amp Service Single Phase And The Inspector Required 3 Rods.

As For The 1 2 3 Rods Idea Thats What I Was Taught.

 

[infinity]

Thanks For The Reply's
I Have Had Jobs That Were State Inspected 300 Amp Service Single Phase And The Inspector Required 3 Rods.

As For The 1 2 3 Rods Idea Thats What I Was Taught.

Maybe this is a local requirement. It is not an NEC requirement.

 

[RUWIREDRITE]

Ground Rods

Ground Rods

To all this may concern, you never need more than 0ne ground rod if you can prove the proper resistance can be acheived by only one rod. I own ground resistance testers and on more than one occasion had to prove our findings to the local jurisdictions. I do pool testing and bonding also and bought this equipment to do all my tests. Remember when you do these tests the ground must be dry to get an average accurate reading.

 

[Dennis Alwon]

To all this may concern, you never need more than 0ne ground rod if you can prove the proper resistance can be acheived by only one rod. I own ground resistance testers and on more than one occasion had to prove our findings to the local jurisdictions. I do pool testing and bonding also and bought this equipment to do all my tests. Remember when you do these tests the ground must be dry to get an average accurate reading.

For me it isn't worth the extra trip to prove it to the inspector nor the cost of the tester. It's cheaper to install 2 rods and be done with it. In this area I am told you will never get 25 ohms to ground anyway even with two rods.

 

[iwire]

How often do you get under 25 ohms with just one rod?

Does adding another rod get it under 25 ohms?

 

[netcom45850]

Thanks For The Info

Thanks For The Info

These Responses Have Been Helpful. Until I Purchase A Ground Resistance Meter I Will Continue To Install Grod Rods As I Have In The Past.

 

[RUWIREDRITE]

tester

tester

Here in the Garden State, I was one of the first contractors to buy one when commericial pool bonding tests became manditory. All of the local jurisdictions know my company well and also knows we carry them on most of our fleet vehicles. I expect from my employees to use them on service installations to see what the resistance is on that given moment(minus the weather conditions). The extra rod doesn't seem to be a big deal to most, but in some cases just trying to get one of those critters in is a chore at best, even with all the new fangled ground rod drivers available. Plus I love to buck authority, when i can,lol. Keeps them guessing.

 

[infinity]

Here in the Garden State, I was one of the first contractors to buy one when commericial pool bonding tests became manditory. All of the local jurisdictions know my company well and also knows we carry them on most of our fleet vehicles. I expect from my employees to use them on service installations to see what the resistance is on that given moment(minus the weather conditions). The extra rod doesn't seem to be a big deal to most, but in some cases just trying to get one of those critters in is a chore at best, even with all the new fangled ground rod drivers available. Plus I love to buck authority, when i can,lol. Keeps them guessing.

But how is the ground rod test cost effective? You would need to be there with the inspector so that he could witness it. This would involve a second trip to the job site. IMO that's a lot more expensive than a $10 rod.

 

[LarryFine]

The extra rod doesn't seem to be a big deal to most, but in some cases just trying to get one of those critters in is a chore at best, even with all the new fangled ground rod drivers available.

I bet my Bosch rotary hammer and rod drivers cost less than one ground tester.

 

[Dennis Alwon]

I bet my Bosch rotary hammer and rod drivers cost less than one ground tester.

That's what I have been using for 20 years. I just replaced my last week. I sometime even drill holes with it.