How many ground rods

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sparky

Member
Location
Pennsylvania
I have a installation for a service replacement in a city row house. We have grounded the incoming 1" copper water pipe with #4 copper and driven one ground rod outside and connected with #6 copper. The inspectors says I need two ground rods. But I think I only need one since my water pipe is my main ground. the rod is supplmental.
 

iwire

Moderator
Staff member
Location
Massachusetts
I agree with the inspector


250.53 Grounding Electrode System Installation.

(D) Metal Underground Water Pipe.
Where used as a
grounding electrode, metal underground water pipe shall
meet the requirements of 250.53(D)(1) and (D)(2).


(2) Supplemental Electrode Required. A metal underground
water pipe shall be supplemented by an additional
electrode of a type specified in 250.52(A)(2) through
(A)(8). Where the supplemental electrode is a rod, pipe, or
plate type, it shall comply with 250.56.
The supplemental
electrode shall be permitted to be bonded to the grounding
electrode conductor, the grounded service-entrance conductor,
the nonflexible grounded service raceway, or any
grounded service enclosure.


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.
 

jetlag

Senior Member
I have a installation for a service replacement in a city row house. We have grounded the incoming 1" copper water pipe with #4 copper and driven one ground rod outside and connected with #6 copper. The inspectors says I need two ground rods. But I think I only need one since my water pipe is my main ground. the rod is supplmental.

Around here the water line is always supplmental and the rods are the main , reason being you have no proof at what point the copper might go to pvc in the ground , or have pvc compression coupling. If you can prove the rod has a max of 25 ohm resistance , it is legal , but it is much easier just to install 2 rods
 

wireguy8169

Senior Member
Location
Southern Maine
While I was working and living in PA I had to do it both ways, if I did not know the area and was in a hurry I just drove two not a big exspense or time thing IMHO, if I was talking to the AHJ I would ask, but I found (worked from the Western to Eastern and many places between) most areas were saying they wanted two and its much to costly to try and prove the less than 25ohms. I know in most of Montgomery county which is just outside of phila. I always had to drive two...hope this helps
 

iwire

Moderator
Staff member
Location
Massachusetts
Around here the water line is always supplmental and the rods are the main , reason being you have no proof at what point the copper might go to pvc in the ground , or have pvc compression coupling. If you can prove the rod has a max of 25 ohm resistance , it is legal , but it is much easier just to install 2 rods

So did your area change the NEC?


A metal underground water pipe shall be supplemented by an additional electrode
 

jxofaltrds

Inspector Mike®
Location
Mike P. Columbus Ohio
Occupation
ESI, PI, RBO
I agree with the inspector

Only one required.

Around here the water line is always supplmental and the rods are the main , reason being you have no proof at what point the copper might go to pvc in the ground , or have pvc compression coupling. If you can prove the rod has a max of 25 ohm resistance , it is legal , but it is much easier just to install 2 rods

Where does it say that I have to 'prove' 25 OHMS to the inspector? I just have to install it that way.

What if it is 25 OHMS on the day that I install it and two days later it does not meet code.

Easier does not make it correct.

I am required to torque some connectors. Who verifies that?

If the inspector wants to test the electrode system, then have at it.

I can install two rods and still not meet the 25 OHMS and be compliant (I disagree). Probably my least favorite rule in the NEC.

If I have a ground rod and it is not less than 25 OHMS I must augment it. If I choose to use another ground rod per 250.56 that ground rod (250.52(A)(5)) is still a single electrode. Yes they form a single grounding electrode 'system'.

I see nothing in 250.56 that says the 25 OHMS does not have to be met.

It is not what we think but what the code 'says'.
 

jetlag

Senior Member
So did your area change the NEC?

Actually all they want here is the the two ground rods . They dont even want the water pipe on residential . ON commercial they want to see the water line before it is covered up if that is the main . If thats changing the code I guess they do , you tell me .
 

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
Actually all they want here is the the two ground rods . They dont even want the water pipe on residential . ON commercial they want to see the water line before it is covered up if that is the main . If thats changing the code I guess they do , you tell me .

It may be more correct to say they are ignoring the requirements of the code.

Roger
 

jetlag

Senior Member
It may be more correct to say they are ignoring the requirements of the code.

Roger

I dont understand what everyone is saying , are you saying in your area you allways have to test for the ohms on ground rods ? I am saying all the residential around here for the past 30 years is plastic water pipe, if you want to use one rod you have to do the ohm test to prove less than 25 ohm. If you use 2 rods on a residence they dont make you do the test. I know the ohms still have to be less than 25 . Each county does test in different areas to determine that 2 - rods always meets the requirements . I dont understand what code they are ignoring , is it not requiring an ohm test on residential with 2 ground rods ?:confused:
 

paul

Senior Member
Location
Snohomish, WA
Here WA modified the code and said if you test and prove 25Ω or less, you're okay. If no test, drive two. Temp power poles only need one, except for the City of Seattle. I learned that one the hard way!
 

jetlag

Senior Member
thanks paul

thanks paul

Here WA modified the code and said if you test and prove 25Ω or less, you're okay. If no test, drive two. Temp power poles only need one, except for the City of Seattle. I learned that one the hard way!

That is the same as required here because the code was modified by the state .But post are saying they ignore the code here, easy is not better and the inspectors must write their own code , Do you know what they are talking about ? :confused:
 
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curt swartz

Electrical Contractor - San Jose, CA
Location
San Jose, CA
Occupation
Electrical Contractor
Actually all they want here is the the two ground rods . They dont even want the water pipe on residential. ON commercial they want to see the water line before it is covered up if that is the main . If thats changing the code I guess they do , you tell me .

The not wanting a water pipe electrode is the code they are ignoring. If you have an underground metal water pipe it must be used as an electrode. It does not matter if the project is residential or commercial. The water pipe is the primary electrode and the ground rods are supplemental. If there isn't an underground metal pipe the interior metal piping must be bonded. If you install a single ground rod the resistance must be less than 25 ohms but the the resistance of 2 or more ground rods is not required to be less than 25 ohms.
 

ericsherman37

Senior Member
Location
Oregon Coast
Oregon forbids the use of a metal underground water pipe as an electrode for existing installations undergoing service change or upgrade. Still have to bond it of course, but it's not usable as a grounding electrode in a GE system. New construction is still required to use metal underground water pipe as an electrode but it has to be supplemented per NEC. But I haven't seen a metal underground water pipe on new construction thus far in my career.

Oregon also requires that 25 ohms for a single rod be proven, otherwise 2 rods is the norm.

Oregon also requires a ufer in ANY construction with reinforced footings (assuming the building or structure will be supplied with power in some manner).

Not that this has any bearing on the original post, just thought I'd share :D
 

LEO2854

Esteemed Member
Location
Ma
Oregon forbids the use of a metal underground water pipe as an electrode for existing installations undergoing service change or upgrade. Still have to bond it of course, but it's not usable as a grounding electrode in a GE system. New construction is still required to use metal underground water pipe as an electrode but it has to be supplemented per NEC. But I haven't seen a metal underground water pipe on new construction thus far in my career.

Oregon also requires that 25 ohms for a single rod be proven, otherwise 2 rods is the norm.

Oregon also requires a ufer in ANY construction with reinforced footings (assuming the building or structure will be supplied with power in some manner).

Not that this has any bearing on the original post, just thought I'd share :D

same here in massachusetts
 

roger

Moderator
Staff member
Location
Fl
Occupation
Retired Electrician
That is the same as required here because the code was modified by the state.
Is there a website we can see GA's modifications on line?
But post are saying they ignore the code here, easy is not better and the inspectors must write their own code , Do you know what they are talking about ? :confused:

Read all of article 250.50 and 250.52 for your answer.

Roger
 
.............sometimes I just do not understand how this section of the NEC is still so misunderstood?????????????????????????:-?


What century is this??? How many books have been written to discuss this topic, how many videos, how many presentations, how many posts ;)


I thought that ostrichs were found in other countries...


This topic will just about become moot anyway, since the adoption of the current NEC code in jurisdictions will not see the need for ground rods if one is smart enough to understand this Part (Part III) of the NEC - for new work.
 
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