logo elektroda
logo elektroda
X
logo elektroda
Advanced Search
logo elektroda

Grounding Pin Depth Dilemma: Increasing Resistance in New Office Building Installation (240m2)

tomhorn1 22065 26
Best answers

Why does the resistance of my driven earth electrode jump from about 60 ohms to 259 ohms as I drive the second rod deeper, and what should I do if I cannot place the rod somewhere else?

The jump usually means the soil around the rod is being compacted badly as it is driven, so the rod ends up in an earthen “pipe” with poor contact and an air gap around it [#17625096] Pour plain water very slowly along the rod so the ground can settle and wrap around it; do not use salted water, because that only gives a temporary reading and can increase corrosion [#17629436][#17630987] If you still cannot get a low enough value, drive another earth electrode in a different spot and bond the electrodes together with a hoop [#19308603] A dedicated soil resistivity-improving material is also mentioned as an option when relocation is impossible [#17624106][#19308603]
Generated by the language model.
ADVERTISEMENT
Treść została przetłumaczona polish » english Zobacz oryginalną wersję tematu
Report a violation of the law
Reply | New topic
  • #1 17623695
    tomhorn1
    Level 10  
    Posts: 21
    Rate: 12
    Hello to you. Have any of you had a similar problem? I make installations in a new office building (240m2) where the builder has not taken into account the earthing, neither the foundation nor the ring. I had to use pins. And now I have a problem .. With the first pin I had a result of 59 ohms, which is 50 too much .. I started hammering the second pin and the result started to increase dramatically. After punching the second one to the end, the result is 259 .. I will add that the MPI meter is new and everything works perfectly on other facilities, including if I measure, for example, on a gas pipe .. (4.7) The area is already developed and not I have the opportunity to look for a different place for a pin. Hammer successively until the score starts to drop?
  • ADVERTISEMENT
  • #2 17623699
    spinacz
    Level 42  
    Posts: 8542
    Help: 1196
    Rate: 2621
    Hit two more and see if you still have to move away to another place, there is no other option.
  • #3 17623748
    CYRUS2
    Level 43  
    Posts: 17641
    Help: 1221
    Rate: 3451
    tomhorn1 wrote:
    On the first spike I had a result of 59 ohms, which is 50 too much.
    Why does my colleague need an earth electrode with a value of 59-50 = 9?
    What is this earth electrode supposed to do - the earth electrode is not a "decorative gadget"
  • #4 17623786
    tomhorn1
    Level 10  
    Posts: 21
    Rate: 12
    I know what an earth electrode is. I mean, as always, a value below 10, usually there is no problem with a value below 5. My question concerns the sense of hammering more, since the value of the second spike jumped so drastically (from 60 to 260). And ultimately, I will emphasize again, I care about the result in the vicinity of 5 ...
  • ADVERTISEMENT
  • #5 17624026
    arcyimperator
    Level 14  
    Posts: 221
    Help: 2
    Rate: 18
    There was such a topic somewhere, the explanation was that the pin bends to the sides when pushed hard and does not stick to the surrounding ground very well (there is air between the pin and the ground). Apparently, over time, the ground begins to stick and the resistance value decreases.
  • #6 17624043
    tomhorn1
    Level 10  
    Posts: 21
    Rate: 12
    My friend Cyrus2, maybe I didn't really express myself very precisely .. I mean the comparison of your experiences in the results at heels, and exactly about such a drastic increase in the result when driving lower. It is known that ultimately I will have nothing else to do but drive another one until the result of 1.28? :D
  • #7 17624046
    kozi966
    VIP Meritorious for electroda.pl  
    Posts: 6922
    Help: 599
    Rate: 1283
    arcyimperator wrote:
    There was such a topic somewhere, the explanation was that the pin bends to the sides when pushed hard and does not stick to the surrounding ground very well (there is air between the pin and the ground). Apparently, over time, the ground begins to stick and the resistance value decreases.


    This subject:
    https://www.elektroda.pl/rtvforum/topic3508820.html#17497437

    My colleague Zbich70 explained it.
  • #8 17624060
    tomhorn1
    Level 10  
    Posts: 21
    Rate: 12
    kozi966 wrote:
    arcyimperator wrote:
    There was such a topic somewhere, the explanation was that the pin bends to the sides when pushed hard and does not stick to the surrounding ground very well (there is air between the pin and the ground). Apparently, over time, the ground begins to stick and the resistance value decreases.


    This subject:
    https://www.elektroda.pl/rtvforum/topic3508820.html#17497437

    My colleague Zbich70 explained it.


    Thank you mate kozi966. I come to the reflection that you will have to hammer elsewhere, although this involves taking apart the cube, which is tightly "stuck" to the building everywhere ..
  • #10 17624117
    tomhorn1
    Level 10  
    Posts: 21
    Rate: 12
    emigrant wrote:
    You can reduce the soil resistivity with such a thing - http://www.budniok.pl/oferta-wg-produktow/sys...em-material-poprawiajacy-rezystywnosc-gruntu/ Does it work? I do not know. Read on, maybe you will find some opinions of people who used it. As if you were not able to connect the vertical earth electrode elsewhere.


    Thank you. I'll check this measure. However, this probably involves the preparation of some excavation, a place to pour it in anyway ..
  • #11 17624124
    emigrant
    Level 29  
    Posts: 1605
    Help: 107
    Rate: 324
    I think so, you need to make such a cylinder around the pin to some depth and pour it. If you decide on this drug, let me know if it did anything.
  • #12 17624127
    tomhorn1
    Level 10  
    Posts: 21
    Rate: 12
    emigrant wrote:
    I think so, you need to make such a cylinder around the pin to some depth and pour it. If you decide on this drug, let me know if it did anything.


    Sure, if I don't come up with anything and I won't do anything, I'll save myself by dismantling the ankle and using this drug. As if what it is, I will describe the effects. But for now - I will probably fight with the next pins, i.e. deeper ...
  • #13 17624491
    CYRUS2
    Level 43  
    Posts: 17641
    Help: 1221
    Rate: 3451
    tomhorn1 wrote:
    My friend Cyrus2, maybe I didn't really express myself very precisely .. I mean comparing your experiences in the results at heels, and exactly about such a drastic increase in the result when you get lower. It is known that ultimately I will have nothing else to do but drive another one until the result of 1.28? :D

    Where did you get that 1.28? ?
    It is an office building powered by a cable network in the TN-C system.
    I suppose.
    The sole purpose of the earth electrode is to work with surge protectors.
    For protectors, the regulations require Ru = 10?.
    If the building does not have a lightning protection system, there will be no surge hazard from the cable line.
    The cable line will suppress surges from the network.
  • #14 17624589
    tomhorn1
    Level 10  
    Posts: 21
    Rate: 12
    These 1.28 ? were a symbol of a good result. Nothing else. And as for the network - yes, it is TN-C, with distribution already in the switchboard to TN-CS. The surge protector is of course installed. ZK on the border of the property is supplied from the overhead line. There is a YKY 5x10 cable from ZK to the building (one core is not used). ZK box still in construction form. The energy company is to put the final ZK there "in a moment".
  • ADVERTISEMENT
  • #15 17624640
    kkas12
    Level 43  
    Posts: 17356
    Help: 1073
    Rate: 4263
    CYRUS2 wrote:
    For protectors, the regulations require Ru = 10?.
    Which recipes?
  • Helpful post
    #16 17625096
    zbich70
    Level 43  
    Posts: 17116
    Help: 1164
    Rate: 6568
    kozi966 wrote:
    My colleague Zbich70 explained it.

    In another thread I also wrote about it, but it is not generally available, so I will quote.
    zbich70 wrote:
    This is because the dry clay looks more like rubble than earth when the groove is dug. During backfilling, it needs to be compacted well so that the lumps break down and cover the hoop well, preferably thicken with layers, the first layer as much as possible so that air spaces near the hoop will disappear.
    The same vertical earth electrode - when driving, the rod breaks to the sides, the clay compacts and, as a result, the rod only has a point contact, because it is in an earthen "pipe". Pouring water into the hole around the rod gives a good effect. Only slowly, it is best to put the hose on the rod and unscrew the tap for minimal seepage, then the water will silt up from the bottom. If it is too fast, it will only become silted from the top and there will be an airbag at the bottom.
    In the same way, the layer above the hoop (about 10-15 cm) can be moistened with water and then run over with a "jumper".

    Over the last quarter of a century I have "made" several hundred earth electrodes for the needs of power networks, including transformer earth electrodes with very restrictive requirements - due to significant earth currents.
    I have no opinion about the so-called linked chemical "soil improvers" - because I have never used them.
    I do not exclude their beneficial influence, although before they were invented, hundreds of thousands of earth electrodes with good parameters were made. And the key to this was - as I have already mentioned - the compaction of the soil around the elements of the earth electrode.
  • #17 17625517
    CYRUS2
    Level 43  
    Posts: 17641
    Help: 1221
    Rate: 3451
    zbich70 wrote:
    Pouring water into the hole around the rod gives a good effect.
    I have no opinion about the so-called linked chemical "soil improvers" - because I have never used them.
    For how long will both be enough.
    tomhorn1 wrote:
    ZK on the border of the property is supplied from the overhead line. There is a YKY 5x10 cable from ZK to the building (one core is not used).
    It is the power line that will not suppress the power surges.
  • #18 17625630
    tomhorn1
    Level 10  
    Posts: 21
    Rate: 12
    Sometimes it's worth admitting when you are wrong. Mine is that I left the measurement of the pin for the so-called dessert, during the overall measurements of the building, after finishing the pavement etc. The investor does not want to hear about taking a cube apart, etc. So tomorrow I will start by slowly pouring water into the crevice that has formed. I will inform colleagues about the results. As a reminder: the first pin had 60 ohms, and the second pin had 257 :) So I will not risk the third so as not to jump to the 1k? ceiling ..
  • ADVERTISEMENT
  • #19 17629185
    gilus1
    Level 29  
    Posts: 1246
    Help: 111
    Rate: 241
    There is a good chance that the earth resistance will decrease for some time with each passing day. I can give my example, where the vertical earth electrode (I do not remember what length) lost more than 50 resistance in 2 weeks. He had something like 11 ohms on the day of the killing, about 5 ohms after 14 days. After that, I didn't measure it anymore, because we finished the work.

    It is true that when driving the probe, the ground breaks down around the probe and there is an air gap around the probe - just move the driven one before putting on the next section.
  • #20 17629261
    zbich70
    Level 43  
    Posts: 17116
    Help: 1164
    Rate: 6568
    gilus1 wrote:
    There is a good chance that the earth resistance will decrease for some time with each passing day.

    Not necessarily. If the ground is clay with a low groundwater level, and additionally covered with a surface that drains rainwater quite efficiently, it will not soon be spontaneous "siltation" of the earth electrode and improvement of the resistance.
    In general, the more urbanized the area is and covered with asphalt or other cubes (as well as drained, canalised), the less chance that the earth electrode will drop spontaneously over time. On the contrary, it can even grow, because the ground, not fed with water from rain or snow, simply dries up.
  • #21 17629285
    tomhorn1
    Level 10  
    Posts: 21
    Rate: 12
    Yesterday I checked again. It dropped from 257 to around 200 ? for two days. In the evening, for an hour, I poured a solution of water with a large amount of salt into the crack. This morning I measured and ..... it dropped to 33? (!) Far from ideal, but there was hope :) . On Monday I will measure again. Possibly, he will strike one more pin and repeat the action with 20 liters of salt water .. I will inform you about the effects :)
  • #22 17629436
    zbich70
    Level 43  
    Posts: 17116
    Help: 1164
    Rate: 6568
    tomhorn1 wrote:
    for an hour I poured a solution of water with a large amount of salt into the gap.

    In my opinion (but only in my opinion) pouring salted water is pointless. Temporarily, with this salt, you will change the soil resistivity and the measurements may turn out great.
    But that's just "powdering" for now so that the meter shows what you want.
    In a moment the salt will "dissipate" in the ground and it will be even worse.

    Pour VERY slowly, plain water, tap water or from a well, without any additives.
    This procedure is not about artificially reducing the resistivity, but about loosening the ground, allowing it to slide down and surround the earth electrode well.
    Only very, very slowly, slower than pissing, so that the water, flowing down the rod, reaches the very bottom and the "wrapping" process begins from below.
  • #23 17629579
    tomhorn1
    Level 10  
    Posts: 21
    Rate: 12
    You're right Zbich, I wanted to see if it would change anything at all. Now I will do it as you suggest. I don't care about the instantaneous result. I am subscribing to it for many years.
  • #24 17629718
    retrofood
    VIP Meritorious for electroda.pl  
    Posts: 31317
    Help: 1140
    Rate: 4781
    tomhorn1 wrote:
    Yesterday I checked again. It dropped from 257 to around 200 ? for two days. In the evening, for an hour, I poured a solution of water with a large amount of salt into the crack. This morning I measured and ..... it dropped to 33? (!) Far from ideal, but there was hope :) . On Monday I will measure again. Possibly, he will strike one more pin and repeat the action with 20 liters of salt water .. I will inform you about the effects :)

    Don't do this, it's self-deception. No one more.
  • #25 17630987
    Darom
    Electrician specialist  
    Posts: 2778
    Help: 231
    Rate: 586
    Hello

    Using table salt is a temporary result. In the long term, it leads to increased corrosion processes - depending on the materials used.
    In the past, you could buy substances that reduce resistance over a long period of time. In Galmar you could buy "Galmar Resistivity". Other manufacturers of lightning protection equipment have similar measures.

    kisses
    - GIFT-
  • #26 17642460
    tomhorn1
    Level 10  
    Posts: 21
    Rate: 12
    Yes, I would like to prophylactically "pour" a special agent slowly. So far, I have knocked out one more pin, and while driving, I tried hard to move the ground around her. Without adding salt water again, I got 11?. In all this situation, it is a success. After the new year, I will approach it with a special liquid and, if necessary, another pin. At the moment, I can only confirm that during driving, the ground ceases to perfectly "wrap" the pin, hence the result increases. At least it was like that in my case. I won't leave any more ground measurements for dessert .. This is where I always start.
  • #27 19308603
    koshin
    Level 11  
    Posts: 22
    tomhorn1 wrote:
    Yes, I would like to prophylactically "pour" a special agent slowly. So far, I have knocked out one more pin, and while driving, I tried hard to move the ground around her. Without adding salt water again, I got 11?. It is a success in this whole situation. After the new year, I will approach it with a special liquid and, if necessary, another pin. At the moment, I can only confirm that during driving, the ground ceases to perfectly "wrap" the pin, hence the result increases. At least it was like that in my case. I will not leave any more ground measurements for dessert .. This is where I will always start.

    In such a situation as it is, it is best to move back to the depth of plunging and establish another earth electrode. Then fasten them together with a hoop. The result will drop by half. Per linked above https://budniok.com.pl/oferta/systemy-uziomowe/gem-material-poprawiajacy-rezystywnosc-gruntu/ from ERICO it works great in rocky ground where you make a hole at least 10cm. From what I read, GEM and GALMAR comply with the PN-EN 62305 standard because they are non-toxic. So they are not chemical "improvers".
    tomhorn1 wrote:
    I know what an earth electrode is. I mean, as always, a value below 10, usually there is no problem with a value below 5. My question concerns the sense of hammering more, since the value of the second spike jumped so drastically (from 60 to 260). And ultimately, I will emphasize again, I care about the result in the vicinity of 5 ...

    Because it results from the resultant soil resistivity. It turns out that the topsoil has a much lower resistivity. Generally, before any grounding, it is not important whether horizontal or vertical, it is necessary to test the soil resistivity so as not to drown an unnecessary ton of steel in the ground.
Reply | New topic
Report a violation of the law

Topic summary

✨ The discussion revolves around the challenges of achieving adequate grounding resistance in a newly constructed 240m2 office building where the builder neglected proper earthing. The initial grounding pin yielded a resistance of 59 ohms, which is excessively high, and subsequent attempts with a second pin resulted in an even higher resistance of 259 ohms. Participants suggest various solutions, including driving additional pins, using soil resistivity improvement materials, and the importance of soil compaction around the electrodes. Some users report that resistance may decrease over time as the soil settles around the pins. The conversation also highlights the necessity of achieving a resistance value below 10 ohms for effective surge protection, particularly in a TN-C electrical system.
Generated by the language model.

FAQ

TL;DR: Driving a second rod without soil contact raised resistance from 59 Ω to 259 Ω (↑339 %). “The rod only has point contact” [Elektroda, zbich70, post #17625096] Compact soil or add parallel rods before chemicals.

Why it matters: High earth resistance weakens surge protection and can violate IEC 62305 limits.

Quick Facts

• Target earth resistance for Type 1 SPD: ≤10 Ω [PN-EN 62305-3]. • Typical 2.4 m copper-bonded rod costs €15–25 [ERICO, 2023]. • GEM backfill lowers resistivity up to 50 % and lasts ≈25 years [nVent, 2022]. • Clay soil resistivity: 30–150 Ω·m when moist; >1000 Ω·m when dry [IEEE Std 80, 2013]. • Saltwater treatment may cut resistance 80 % for days but triples corrosion rate [Elektroda, Darom, post #17630987]

Why did resistance jump from 59 Ω to 259 Ω after the second pin?

The rod bent, leaving an air gap, so only its tip touched soil. Air raises contact resistance dramatically [Elektroda, zbich70, post #17625096]

Should I keep hammering deeper or start a new location?

Stop when resistance rises. Install another vertical rod 2–3 m away and bond both; parallel rods roughly halve resistance [Koshin, #19308603].

What resistance is acceptable for an office fed by TN-C/S without lightning protection?

For surge protective devices a value ≤10 Ω is recommended by IEC 62305-3; lower figures (≤5 Ω) add safety margin [PN-EN 62305-3].

Does pouring plain water really help?

Yes. Slow watering collapses the soil around the rod, restoring full contact and lowering resistance within days [Elektroda, tomhorn1, post #17629285]

Is using saltwater a good long-term fix?

No. Salt gives a quick drop but leaches away and accelerates metal corrosion, raising resistance later [Elektroda, Darom, post #17630987]

What commercial compounds work better than salt?

Graphite-cement GEM or Galmar Resistivity backfill stays conductive for about 25 years and is non-toxic [nVent, 2022].

Could high resistance damage surge protectors?

Yes. If Ru exceeds 10 Ω, Type 1 SPD let-through voltage can rise 30 – 50 %, risking equipment failure during a surge [Schneider, 2021].

Edge case: what if soil tests over 2000 Ω·m?

Install horizontal ring conductors, multiple deep rods, or drilled wells with conductive backfill; chemicals alone will not meet specs in very resistive rock [IEEE Std 80, 2013].

How do I test soil resistivity before choosing an electrode type?

Use the four-pin Wenner method at 0.5, 1, 2, and 4 m spacings; average readings guide design [IEC 60479].

Can I reduce resistance by bonding to metal piping?

Yes, bonding to buried metal gas or water pipes often cuts resistance below 5 Ω, provided local codes allow it [Elektroda, tomhorn1, post #17623695]
Generated by the language model.
ADVERTISEMENT