[Kpack]

I only have one gr rod for my home I live in Bryan tx I don't know a lot about it and I've never heard of 2 gd rods here what is the purpose of 2 I've been hearing y'all talk about.

 

[Jim Port]

Unless it can be proved that the one rod is enough to get the resistance down below 25 ohms the code requires an additional electrode. It is easier to drive two rods and be down with it and avoid the need to show the inspector your testing of the one rod.

Once the second electrode is driven there is no requirement to keep adding electrodes to get below 25 ohms.

 

[sublime2]

I believe the 2 ground rods were decided as an alternate to the one.with just one rod,code requires a rather expensive test to determine if it will fall below a certain #. I think 2 rods will not give you any more protection then the one you already have.

 

[J. V.]

I have only one myself. It was inspected when I did the service upgrade about 15 years ago. I have no intentions to install another one, nor am I required to.

 

[NJMarine]

I believe the 2 ground rods were decided as an alternate to the one.with just one rod,code requires a rather expensive test to determine if it will fall below a certain #. I think 2 rods will not give you any more protection then the one you already have.

It will give you more protection since each ground rod is on a different ground plane.

 

[sublime2]

It will give you more protection since each ground rod is on a different ground plane.

In theory.

 

[Dave632]

Two ground rods will lower the effective resistance to ground, thus providing a more conductive path. For example, if each ground rod is 30 ohms, two ground rods in parallel will present a resistance of 15 ohms. The lower the resistance, the more current will flow to ground, as opposed to some alternate path.

 

[bernie963]

this and other recent ground rod discussions prompts me to ask the following question. If a service is bonded to an incoming copper water service, is any better protection provided by one or more ground rods? In my case the water service is about 40 feet away from the service entrance panel and any additional ground rods would be within a couple of feet of the panel. I understand that the cold water service ground met the code when the house was built in 1985. The copper water service is about 50 feet long to the street which is a cast iron main.

bernie

 

[electures]

I believe the 2 ground rods were decided as an alternate to the one.with just one rod,code requires a rather expensive test to determine if it will fall below a certain #. I think 2 rods will not give you any more protection then the one you already have.

The NEC does not require test. The inspector can request a megger test. Since he has to witness the test and can take several days to get to the job for the test. It is easier to drive the second rod and forget about it. Otherwise the EC can sit and wait for the EI to witness the test. If the test proves less than 25 ohms, no second rod is required.

 

[sublime2]

The NEC does not require test. The inspector can request a megger test. Since he has to witness the test and can take several days to get to the job for the test. It is easier to drive the second rod and forget about it. Otherwise the EC can sit and wait for the EI to witness the test. If the test proves less than 25 ohms, no second rod is required.

Well if there's no test then how does one know that 2 rods will do the job and not just one rod?

 

[electures]

Well if there's no test then how does one know that 2 rods will do the job and not just one rod?

We don't. The NEC does not require more then two rods. I don't require the second rod. But if there is only one rod, I request the megger test. I have three days to complete the inspection including witness the test. It is cheaper to just drive two rods and be done with it.

 

[bobelectric]

Look up your power company provider web site on installation requirements.They require us to use 2 rods at least 6 feet apart,no asterick about only 1 if you can show 1 rod does the job. This is for new installs of course,not existing.

 

[AllanJ]

I should ask, if the building has an entering water pipe or a concrete reinforcing bar as a grounding electrode, is just one ground rod sufficient?

 

[Kpack]

I should ask, if the building has an entering water pipe or a concrete reinforcing bar as a grounding electrode, is just one ground rod sufficient?

Hey Allen you may have to start a new thread on that to get a answer

 

[k_buz]

I should ask, if the building has an entering water pipe or a concrete reinforcing bar as a grounding electrode, is just one ground rod sufficient?

No. If you use rod, you must be less than 25 ohms or drive a second rod. Even if you have properly bonded the other electrodes.

Note: There is some issues that do arise with Ufers. Some people will tell you that all you need to do is bond to the Ufer and nothing else. However, in my area, the Ufer only takes the place of the rods, and you will have to bond to water if present.

 

[Norcal]

I have only one myself. It was inspected when I did the service upgrade about 15 years ago. I have no intentions to install another one, nor am I required to.

If the installation met the code in effect when it was done/inspected there is no need or requirement to "upgrade" to newer code requirements. The NEC is not retroactive. To put it simple, I agree w/ the quote above.