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What Is a Good Ground Resistance Value?
What Is a Good Ground Resistance Value?

Zero Ohms… Not Really!

The goal in ground resistance is to achieve the lowest ground resistance value possible, that makes sense economically and physically, when contacting the earth, also known as the soil/ground rod interface.

Ideally, a ground should be zero ohms of resistance, but…

Unfortunately, there is not one standard ground resistance threshold recognized by all certifying agencies.

The NFPA and IEEE recommend a ground resistance value of 5 ohms or less while the NEC has stated to “Make sure that system impedance to ground is less than 5 ohms specified in NEC 50.56. In facilities with sensitive equipment it should be 5ohms or less.

Copper Earth Rod thermoweld connection at a 33kV Substation in Nakheel, UAE
Copper Earth Rod thermoweld connection at a 33kV Substation in Nakheel, UAE (photo by Muhammad Adnan; Substation Designer via Flickr)

The telecommunications industry has often used 5 ohms or less as their value for grounding and bonding while electric utilities construct their ground systems so that the resistance at a large station will be no more than a few tenths of one ohm.

In general, the lower the ground resistance, the safer the system is considered to be.

Reference: Fluke Earth Ground Testing Fact – Distributor Training Program

About Author //

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Edvard Csanyi

Edvard - Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV high power busbar trunking (<6300A) in power substations, buildings and industry fascilities. Designing of LV/MV switchgears.Professional in AutoCAD programming and web-design.Present on

30 Comments


  1. Tunji
    Nov 25, 2016

    Good enough. Thanks Edvard


  2. trisha gupta
    Aug 22, 2016

    How to measure the value of earth resistance in Multi-Dwelling Unit(Apartments) where neither the earth pit is not accessible, nor the earthing rod?

    Are there any non destructive methods available? By non destructive, I mean without digging?


    • Imran Malik
      Oct 25, 2016

      You may Rap around the ground cable to water pipe. it will reduce the grounding resistance.


  3. suzzanae
    Jun 22, 2016

    Hi, I would like to know whether we can achieve 5 ohm for more than 10 years or not.
    And, can we suggest type of earthing just differentiating wet soil, sand soil or rocky soil without calculation. if any standard thumb rule are there please share .

    Also. LPS for metallic tower and not metallic tower .


  4. gilbert
    May 14, 2016

    may i ask some question reguardimg on bonding of grounding,? how come that it is more efficient my grounding system if i’m goin g to bond the grounding of my lightning arrester in a building grounding? if a high voltgage and current occur cause by a lightning,. do i have a current pass through my equipments which is grounded (connected to a building grounding )???


  5. Jimmy Jones
    Dec 11, 2015

    If I turn off all breakers in my homes main breaker panel and remove the main Neutral Wire from the panel tie point, then run a wire from one unused 120 volt 20 amp breaker to ground the breaker should clear if the ground is sufficient. Right? If it doesn’t clear, then the ground must be over 5 or 6 ohms. I know this is dangerous and I’m not recommending anyone doing it but am I correct in what I’m saying here? I’ve seen people try to obtain this 5 ohms or less ground and never come close to obtaining a low enough resistance reading by itself to clear the breaker.


  6. v.ragu
    Dec 11, 2015

    In my experience we could achieve close to zero that if all the earth rod are interconnected


  7. muhammad salam
    Oct 16, 2015

    whats the domestic,human,and industrial value of grounging


  8. Salman Kamal
    Oct 13, 2015

    Although zero ohm is the most ideal figure, but it is not always the case, in my experience along, there are many solution to make nearby zero, such as carbon and salt arrangement with many earth copper rods connected together and surrounding the premises such as substation. The worst case where you have Stoney ground area with a lack of humidity or source of water.


  9. MIUNSHYA MUSONDA
    Sep 04, 2015

    Hi i want to know the recommended earth resistance value for electrical installation


  10. diolan
    Aug 31, 2015

    hello edvard, the article of the nec is the 250.56 and the value shall be less than 25 ohms. In the article is missin the number “2”.


  11. surya
    May 03, 2015

    so ….we cannot find earth resistance practically


    • Girish R Pillai
      Feb 22, 2016

      We can find earth resistance practically. Earth resistance tester with 3 points or a clamp on type meter will help. Its easy to operate.


  12. joseph
    Apr 21, 2015

    What it’s the purpose of earth megger


  13. Suresh
    Jan 02, 2015

    straight answer to my question. most useful site. Thanq

    • Edvard
      Edvard
      Jan 03, 2015

      You’re welcome Suresh! Straight to the point!


  14. emad hassoun
    Oct 15, 2014

    Very nice shorted ( concetrated information) ….I hope to see more like that ….. thank


  15. godwin
    Oct 15, 2014

    I really like a site like this, were I can reffer some of my engineering questions to. I would like to know how to test a lightning arrestor that is mounted on a mast with a copper tape running down to earth pit?


  16. ghulamsarwar
    Aug 03, 2014

    well this z vry good site for electrical information,,,,v r getting a vry low resistance with copper groundind rod almost 1 ohm……& less than 5 ohm with galvanized steel rod of 19mm dia with 24mm lenght,


  17. Vivek
    Jun 06, 2014

    I have been searching a site like this for quite a long time. I’ve finally discovered the site for all my electrical references. I feel really happy for the good work you do, Edvard. Thanks a lot…


  18. ashraf
    Jun 06, 2014

    Dear Edvard.
    That is so good information , you are professional and I would like to keep in touch with you.
    Thanks
    Sincerely.
    Engineer.
    Bush. Ashraf


  19. ouadi
    May 26, 2014

  20. shrikant
    May 10, 2014

    describe 4 point earth resistance measurement method,


    • Girish R Pillai
      Feb 22, 2016

      Its very easy and explained on the meter itself in simple language. To arrange the spikes in a straight line at measured intervals. Apply current by pressing the push button. Note the reading and calculate based on the formula which is inversely proportional to the distance between spikes.


  21. Raj
    Apr 24, 2014

    In house we get 7 to 5 ohms.


  22. ashish
    Feb 02, 2014

    my think bildup


  23. Sohail Khan
    Dec 29, 2013

    Nice information about earthing resistance….


  24. iwak
    Dec 25, 2013

    where i can informasi accurate troubleshooting electrical,i m from indonesia,write english no good

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