Main panel grounding

[Dave85]

I have not done much electrical in a while and so I am rusty when it comes to what needs to be done so I thought I'd run this by everyone to see if I was correct.

We have a 150A main panel with a 60A sub right next to it.
The house currently only has one grounding rod and so I believe it needs to be upgraded to two rods 7 feet apart and about 2 feet from the foundation.
The wire should be bare stranded 6 gauge.

Am I correct?

Thanks for the help

 

[mcclary's electrical]

Is there a water pipe foe GEC???? If so,,,,you only need one rod. If you want two anyway, I would use a #6 solid bare.

 

[Dennis Alwon]

I have not done much electrical in a while and so I am rusty when it comes to what needs to be done so I thought I'd run this by everyone to see if I was correct.

We have a 150A main panel with a 60A sub right next to it.
The house currently only has one grounding rod and so I believe it needs to be upgraded to two rods 7 feet apart and about 2 feet from the foundation.
The wire should be bare stranded 6 gauge.

Am I correct?

Thanks for the help

2 rods at least 6 piece apart but the further the better. The wires needs to be copper-- solid or stranded cover or bare #6

Also as stated water pipe should be bonded if they are metal.

 

[GMc]

You beat me to it Dennis.

After reading 250.56 I ws going to say the same. (2 rods)

edit to add (2 rods)

 

[mcclary's electrical]

You don't need two with a metal water pipe GEC you only need ONE 250.53(d) 2

 

[GMc]

You don't need two with a metal water pipe GEC you only need ONE 250.53(d) 2

Article 250.56 Requires the resistance of Ground Rods to be 25 OHMs or less. Otherwise we are required to drive a second rod.

 

[Dennis Alwon]

You don't need two with a metal water pipe GEC you only need ONE 250.53(d) 2

Yes, and if you read 250.53(D)(2) it directs you to 250.56. Two rods are required unless you can get 25ohms with one rod. Generally that cannot be done so 2 rods are the MO for most of us.

 

[mcclary's electrical]

You're right, Ive just never had them test one rod. If I'm on a metal pipe for primary ground, I'll use one rod for secondary. If rods are primary, I drive two.

 

[ivsenroute]

You don't need two with a metal water pipe GEC you only need ONE 250.53(d) 2

I shared this opinion as an inspector at one time and was corrected after an in person conversation with one of the NEC panel members who let me know the intent of that section of the code. I was corrected. What was fun was making the electricians that I was previously allowing this add the 2nd rod. I simply told them the truth that I was wrong in the past, I was corrected by the proper authorities and now a 2nd rod is required.

Unless you can prove <25 ohms to earth then a 2nd rod is required even if you attach to a metal water pipe.

If everyone would use a CEE for additions and new construction then we would not have to worry about the ground rods at all.

 

[infinity]

You're right, Ive just never had them test one rod. If I'm on a metal pipe for primary ground, I'll use one rod for secondary. If rods are primary, I drive two.

There really is no code definition of primary and secondary electrodes. If the water pipe is present and qualifies as an electrode then it must used. It's required that the water pipe electrode be supplemented by another electrode. If you choose to do so using ground rods then a single rod must have a resistance of 25 ohms or less. Rather than try to prove that the rod actually has this resistance we simply pound in two rods and call it a day.

As Ivsenroute said, with most new construction, you would be using the CEE so the ground rods wouldn't be needed at all since the CEE can serve as the supplemental electrode for the water pipe.

 

[iwire]

There really is no code definition of primary and secondary electrodes.

I am glad you brought that up, I see it often in these forums and wonder where it comes from?

 

[infinity]

I am glad you brought that up, I see it often in these forums and wonder where it comes from?

I hear this too and wonder where the myth of primary and secondary electrodes originated. I'd guess that since the water pipe must be used and supplemented you might consider that the primary electrode and the supplemental electrode the secondary. Of course that goes out the window when you have a CEE or building steel present too since those are not made electrodes like a ground rod would be.

 

[mcclary's electrical]

I call them p&S because say for instance on a 200 amp service, if there's a water pipe GEC,,,,it would take a #4,,,,,and then the rods could be #6,,,,,but if there is no pipe GEC ,,,then the rods would become #4(and what I call primary),,,,,,,no these terms don't match NEC,,,,,I should have said "supplemental" But I stil seperate them in terms becasuse if there was NO DIFFERENCE,,,,,there would be a #4 on both

 

[Dennis Alwon]

I call them p&S because say for instance on a 200 amp service, if there's a water pipe GEC,,,,it would take a #4,,,,,and then the rods could be #6,,,,,but if there is no pipe GEC ,,,then the rods would become #4(and what I call primary),,,,,,,no these terms don't match NEC,,,,,I should have said "supplemental" But I stil seperate them in terms becasuse if there was NO DIFFERENCE,,,,,there would be a #4 on both

Even if the water pipe is non metallic you still only need a #6 to the rods.

 

[infinity]

Even if the water pipe is non metallic you still only need a #6 to the rods.

As Dennis pointed out that's all that is required to a rod regardless of the size of the service entrance conductors. IMO the use of the words primary and secondary is confusing but that just me.

 

[iwire]

for instance on a 200 amp service, if there's a water pipe GEC,,,,it would take a #4,,,,,and then the rods could be #6,,,,,but if there is no pipe GEC ,,,then the rods would become #4

If you built a 4000 amp 480 volt service in an area with no electrodes you could meet code with just one or two rods connected to the service with just 6 AWG.

The rod can not 'connect' to the dirt well enough to require more than a 6 AWG.

 

[Rockyd]

People need to understand the difference between grounding and bonding. Mike Holt writes a great book called Grounding VS Bonding -

In a nutshell 250.4 (A) covers it, but a lot of people miss it, the first few times (and some never do "get it").

See 250.4(A)(1) Electrical systems that are grounded shall be conected to the earth in a manner that willl limit the voltage imposed by lightning, line surges, or unintensionsal contact with higher voltage lines and that will stabilize the voltage to earth.

So one will realize that grounding has nothing to do with bonding in purpose.

Now read 250.4 (A)(3) Normally non-current-electrically conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected together and to the electrical supply source in a manner that establishes an effective ground fault current path.

Bonding is for tripping OCPD's.

Grounding is for drainage of higher voltages to earth. See the FPN at the bottom of 250.4(A)(1) about methodology in proper installation.

 

[romeo]

Main panel grounding

You don't need two with a metal water pipe GEC you only need ONE 250.53(d) 2

2 rods needed at least 6 ft. apart. or show 25 ohm Resistance in the first one. 250.56

 

[romeo]

Main bonding electrode

Main bonding electrode

If you built a 4000 amp 480 volt service in an area with no electrodes you could meet code with just one or two rods connected to the service with just 6 AWG.

The rod can not 'connect' to the dirt well enough to require more than a 6 AWG.

I agree

thought it had something to do with the speed of lightning.

 

[Dennis Alwon]

The rod can not 'connect' to the dirt well enough to require more than a 6 AWG.

And yet some EE's require a 3/0 to the rod. Go figure.