250.53 B ground rod spacing

[Legrand]

I know we drive ground rods 6' apart, is that per NEC? It just does'nt read that way to me for a single service.

 

[Dennis Alwon]

I know we drive ground rods 6' apart, is that per NEC? It just does'nt read that way to me for a single service.

We drive ground rods at least 6 feet apart. I am confused by your statement. Where in 250.53(b) does the wording exempt a single service.

You must use 2 ground rods unless you can get 25 ohms on one single rod. Generally it is easier to just drive two rods. 250.56

 

[bphgravity]

I agree with Dennis. Why are you driving two rods?

The first rod is all that is required per code, unless you don't comply with 250.56. 250.56 tells you to drive the second rod and space them 6' apart from esch other.

250.53(B) is not exactly the correct section to reference for this question.

 

[charlie]

I know we drive ground rods 6' apart, is that per NEC? It just doesn't read that way to me for a single service.

"250.53(B) Electrode Spacing. Where more than one of the electrodes of the type specified in 250.52(A)(5) or (A)(7) are used, each electrode of one grounding system (including that used for air terminals) shall not be less than 1.83 m (6 ft) from any other electrode of another grounding system. Two or more grounding electrodes that are bonded together shall be considered a single grounding electrode system."
​

There is no exception for single services and the ground rods are not to be closer than 6 feet to each other. However, ground rods may be and are recommended to be their length apart. If you use 8 ft. grounding electrodes, space them 8 ft. apart. The reason is that they work better.

 

[infinity]

I would add that it's highly likely for a service in a new building that would never need any ground rods since you would be using the CEE.

 

[weressl]

I know we drive ground rods 6' apart, is that per NEC? It just does'nt read that way to me for a single service.

It odes not. If you have a grounding system for your service AND you have grounding electrodes for lighting protection then the electrodes of the two different systems should be separated 6' from each other.

 

[Legrand]

"250.53(B) Electrode Spacing. Where more than one of the electrodes of the type specified in 250.52(A)(5) or (A)(7) are used, each electrode of one grounding system (including that used for air terminals) shall not be less than 1.83 m (6 ft) from any other electrode of another grounding system. Two or more grounding electrodes that are bonded together shall be considered a single grounding electrode system."

So they just can't be within 6' of another system so my two rods for the same service could be alot closer no? I don't even know why I brought this up, it does'nt really matter but thats just how I read it and it does'nt seem right.

 

[Dennis Alwon]

"250.53(B) Electrode Spacing. Where more than one of the electrodes of the type specified in 250.52(A)(5) or (A)(7) are used, each electrode of one grounding system (including that used for air terminals) shall not be less than 1.83 m (6 ft) from any other electrode of another grounding system. Two or more grounding electrodes that are bonded together shall be considered a single grounding electrode system."

So they just can't be within 6' of another system so my two rods for the same service could be alot closer no? I don't even know why I brought this up, it does'nt really matter but thats just how I read it and it does'nt seem right.

No. The electrodes must be at least 6' apart. It is recommended by some to be 16' apart for 8 foot rods.

 

[raider1]

"250.53(B) Electrode Spacing. Where more than one of the electrodes of the type specified in 250.52(A)(5) or (A)(7) are used, each electrode of one grounding system (including that used for air terminals) shall not be less than 1.83 m (6 ft) from any other electrode of another grounding system. Two or more grounding electrodes that are bonded together shall be considered a single grounding electrode system."

So they just can't be within 6' of another system so my two rods for the same service could be alot closer no? I don't even know why I brought this up, it does'nt really matter but thats just how I read it and it does'nt seem right.

If you are driving a second rod to meet the requirements of 250.56 then the rods must be at least 6' apart.

250.56 Resistance of Rod, Pipe, and Plate Electrodes.
A single electrode consisting of a rod, pipe, or plate that does not have a resistance to ground of 25 ohms or less shall be augmented by one additional electrode of any of the types specified by 250.52(A)(4) through (A)(8). Where multiple rod, pipe, or plate electrodes are installed to meet the requirements of this section, they shall not be less than 1.8 m (6 ft) apart.

Chris

 

[raider1]

No. The electrodes must be at least 6' apart. It is recommended by some to be 16' apart for 8 foot rods.

Now who would recomend ground rods be 16' apart.

Chris

 

[Legrand]

250.56 Resistance of Rod, Pipe, and Plate Electrodes.
A single electrode consisting of a rod, pipe, or plate that does not have a resistance to ground of 25 ohms or less shall be augmented by one additional electrode of any of the types specified by 250.52(A)(4) through (A)(8). Where multiple rod, pipe, or plate electrodes are installed to meet the requirements of this section, they shall not be less than 1.8 m (6 ft) apart.

That's what I was looking for, thanks again Chris.

 

[raider1]

You are very welcome.

Chris

 

[Dennis Alwon]

250.56 Resistance of Rod, Pipe, and Plate Electrodes.
A single electrode consisting of a rod, pipe, or plate that does not have a resistance to ground of 25 ohms or less shall be augmented by one additional electrode of any of the types specified by 250.52(A)(4) through (A)(8). Where multiple rod, pipe, or plate electrodes are installed to meet the requirements of this section, they shall not be less than 1.8 m (6 ft) apart.

That's what I was looking for, thanks again Chris.

I posted that article in the #2 Post. Guess you missed it. :smile:

 

[raider1]

I posted that article in the #2 Post. Guess you missed it. :smile:

Yes you did Dennis, I just cut and pasted the entire section.

Chris

 

[alfiesauce]

CEC requires two rods at 10'.
or one ground plate..
not that that matters.

 

[Legrand]

Man, I'm sorry Dennis, you were right on top of it. Thanks to all of you guys, I really appreciate you guys pulling my head out of my....

 

[e57]

OK now lets have fun - how far do those rods need to be from the water pipe? Zero - why? Given that rods operate better further apart - would it not make sense that the rod suplimenting it be more that 6' away as well?

 

[bphgravity]

According to the NFPA 780 - A.4.13.2.4:

No benefit is gained from the second ground rod if placed closer than the length of the longer rod. No addtional benefit is gained if the second rod is placed over four times the length of the longer rod.

 

[infinity]

OK now lets have fun - how far do those rods need to be from the water pipe? Zero - why? Given that rods operate better further apart - would it not make sense that the rod supplementing it be more that 6' away as well?

The supplementation is so that if the water pipe were changed to a plastic pipe that the two rods would now be the GES. So no spacing is required for the supplemental electrode from the water pipe.

 

[weressl]

If you are driving a second rod to meet the requirements of 250.56 then the rods must be at least 6' apart.

250.56 Resistance of Rod, Pipe, and Plate Electrodes.
A single electrode consisting of a rod, pipe, or plate that does not have a resistance to ground of 25 ohms or less shall be augmented by one additional electrode of any of the types specified by 250.52(A)(4) through (A)(8). Where multiple rod, pipe, or plate electrodes are installed to meet the requirements of this section, they shall not be less than 1.8 m (6 ft) apart.

Chris

If the NEC is NOT an engineering document, I wonder why this restriction exist. There is no safety issue here, so why is the Code taking a stance? Electrodes placed closer than 6' to each other can also produce the desired value.