Interpretation on supplemental ground rods

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ivsenroute

Senior Member
Location
Florida
Here is the scenario.

Existing 100 amp overhead service being replaced to include meter base and feed to the existing untouched main panel.

As part of this installation a supplemental rod was installed in addition to the existing grounding system attached to the copper water main. Green #6 THHN copper was run to the rod.

The hot and cold copper pipe was bonded along with the black gas pipe.

Inspector wants another rod installed or prove the <25ohm rule.

Contractor states the existing house and service only had one grounding point at the water main which worked great for years, the panel was not being replaced and the added supplemental rod was a bonus, as was the bonding of the water pipe and gas black pipe. One rod added now means there are 2 grounding points.

Inspector states that the water main is the main grounding system and the rod is supplemental and all supplemental rods either need to prove the 25 ohm rule or add a second.

What is your experience and opinion?
 

ivsenroute

Senior Member
Location
Florida
One more item of note.

So a home fed by a plastic pipe from a well or plastic public water feed only needs 2 rods if the 25 ohm rule cannot be verified.

BUT

A home fed by a metal water pipe suitable for grounding must also have 2 ground rods (barring the 25ohm rule) which means that it will need 3 connections to ground vs only 2 for a house with no metal water pipe feed.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
ivsenroute said:
One more item of note.

So a home fed by a plastic pipe from a well or plastic public water feed only needs 2 rods if the 25 ohm rule cannot be verified.

BUT

A home fed by a metal water pipe suitable for grounding must also have 2 ground rods (barring the 25ohm rule) which means that it will need 3 connections to ground vs only 2 for a house with no metal water pipe feed.

This is correct
 

cowboyjwc

Moderator
Staff member
Location
Simi Valley, CA
I came up on this when I was doing a service change and was told I could add the ground rod or dig up the yard to prove that there was still 10' of metalic water pipe in the ground.

You had to bond the water pipe regardless of whether you put in two ground rods or not. I also agree with Scott about the gas line.
 

svemike

Member
Location
Sonoma, CA
I must be missing something. 2005 NEC 250.53 (D) (2) states "an additional" meaning one, must be installed. Another (#2) if 25 ohms cannot be achieved. How does that make it 2 automatically before an ohm test failure?
 

George Stolz

Moderator
Staff member
Location
Windsor, CO NEC: 2017
Occupation
Service Manager
I'm not quite sure what you're saying, but if he drives two ground rods, he doesn't have to test their resistance to earth. He can simply walk away from the installation with the rods cumulatively resisting the earth at a million ohms or more. :)
 

svemike

Member
Location
Sonoma, CA
If you lived where I do, you would do anything to avoid ANY ground rods, but if you were lucky enough to get one in 8 ft, why try two if not necessary. In this area, the AHJ does not require ohm test. Service changes often do not have access for trenchers or backhoes on any part of property, and if you could hand dig in seriously rocky soil for 2-1/2 ft deep trench alternative, you could pound a ground rod. This is the biggest unknown for my service changes. I don't have a gigantic jack hammer with a trailer mounted compressor that can drive thru rock like the Utility has. As an aside, in good soil, I normally start the ground rod with a head start within the trench the conduit is in, but an inspector once required me to install the rod in "virgin" soil, outside the trench. Can't find any reference to that issue in the NEC. Any comments?
 

George Stolz

Moderator
Staff member
Location
Windsor, CO NEC: 2017
Occupation
Service Manager
svemike said:
If you lived where I do, you would do anything to avoid ANY ground rods, but if you were lucky enough to get one in 8 ft, why try two if not necessary. In this area, the AHJ does not require ohm test. Service changes often do not have access for trenchers or backhoes on any part of property, and if you could hand dig in seriously rocky soil for 2-1/2 ft deep trench alternative, you could pound a ground rod. This is the biggest unknown for my service changes. I don't have a gigantic jack hammer with a trailer mounted compressor that can drive thru rock like the Utility has.
The dog ate my homework too, but I will still drive two ground rods if required. :D

As an aside, in good soil, I normally start the ground rod with a head start within the trench the conduit is in, but an inspector once required me to install the rod in "virgin" soil, outside the trench. Can't find any reference to that issue in the NEC. Any comments?
It's nonsense. How was your poker face when he said that? :)

Although, an inspector that frequents this forum once accidentally jumped on a ground rod, driving it through his abdomen - hearing that story prompted me to never leave a half driven rod in a trench ever again. I still shiver thinking about it.
 

cowboyjwc

Moderator
Staff member
Location
Simi Valley, CA
George Stolz said:
Although, an inspector that frequents this forum once accidentally jumped on a ground rod, driving it through his abdomen - hearing that story prompted me to never leave a half driven rod in a trench ever again. I still shiver thinking about it.

Owwwwwwwwwww
 

George Stolz

Moderator
Staff member
Location
Windsor, CO NEC: 2017
Occupation
Service Manager
I thought it was you - it was an inspector in CA. I just went looking and couldn't find it.
icon9.gif
 

cowboyjwc

Moderator
Staff member
Location
Simi Valley, CA
George Stolz said:
I thought it was you - it was an inspector in CA. I just went looking and couldn't find it.
icon9.gif

Nope, I've been real lucky in 30+ years in the trade the worse I got was 5 stiches in a knuckle.

I did take a tumble a couple of years back as an inspector and got up thinking I was fine, about two hours later it was all I could do to straighten out my arm, and it felt like a truck snuck up on me and ran me over. Nothing broken, but I was sure sore for a week or two.

But no ground rods stuck any where, though there have been suggestions.:D
 

sguinn

Senior Member
Location
Blue Ridge, Ga
I "ask" that elec. drive two ground rods or show resistance, haven't had anyone test yet, they just drive the second one and go on with life. Not to get off the thread too much but after ten years in the trade, nothing but the occasional cut or sore back, but after year and a half of inspecting I've been:

1)Struck by lightning
2)In a head on collision(last inspection of the day)(Also not my fault):-?
 
AHJ's in my area "require" the second ground rod for any service upgrade where the 25ohm rule cannot be proven. I tend to agree with this. Just drive it or put it in a trench. It's not like it costs a heck of a lot.

As for the gas grounding we are now "required" to run a #6 bare copper or larger, or a #1 AL or larger, ground from the "point of service entry (where the gas line enters the dwelling) to the "point of electrical service entry" (where the Meter Base is). This is still required even if the gas line is entirely copper, or iron, or SS flex.
 
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