Fence Grounding

[JWall886]

I have been looking at these standards in the NEC and have tried to look into the NESC (which I know isn't relevant for this situation as it is not a substation) but haven't found a good answer. We're looking at installing a new fence around a station with a CP (Cathodic Protection) system and it is our standard to have the fence be grounded. This particular station is closest ~80 feet to anything besides the incoming and outgoing pipes running under the fence that have the CP system associated with it (much further than the NEC required 16ft for fence grounding). From my understanding it doesn't need to be grounded in this scenario but that is company standards and not a hill I am willing to die on.

All this being said, I can't find anywhere what the maximum distance that is accepted as okay to space grounding rods along the fence. I know about the bonding jumpers length (160 ft) and that the gate posts need to be connected to the grounding system but otherwise I can't find anything anywhere. Our company standard is 20 feet which with the size of our fences, plus the lack of actual need to ground the fence, is frivolous imo but I'm trying to find something to back a number up by instead of picking an arbitrary number for when we look to update the standards.

 

[electrofelon]

Isn't the fence already grounded? Or are the posts mounted on plastic piles of some sort?

 

[Dsg319]

Isn't the fence already grounded? Or are the posts mounted on plastic piles of some sort?

He likely is in a natural gas or oil facility. Where refunding fence grounding/bonding is done.


Most company have their own spec on this.

You likely won’t find anything regarding this in the NEC to satisfy a gas company standard for fence grounding/bonding.

I believe the NEC only hits on likely to become energized and fencing around overhead conductors/substation work.

Correct me if I’m wrong

Maybe try IEEE green book

 

[Fred B]

I know the fence around a cell tower has to be bonded.

Likely the company came up with the 20ft number basis to maintain a consistent gradient along the perimeter of the fence given your typical soil conditions.
This number could be adjusted up or down with ground resistance testing for the specific conditions at the location if you really want to get that involved.

2026 NFPA-780 has some information for fences grounding and bonding in article

4.15.5 * Metallic Fences.​

and the appendix A.4.15.5

 

[garbo]

Isn't the fence already grounded? Or are the posts mounted on plastic piles of some sort?

Years ago we had a long tractor trailer scale a few feet from a several hundred foot long 8' high fence. Several times a year at least one to all four load cells would burn out after storms..Tech who replaced the load cells & serviced the scale recommended that we Install a ground rod at each end of fence nearest two ends of k scale. Fence post were set into maybe 2' of concrete. Anyway we installed ground rods and ran a #6 copper wire from first ground rod to holes drilled & tapped in every steel fence post along scale. Until p!ace closed down a few years later no load cells burned out.

 

[JWall886]

He likely is in a natural gas or oil facility. Where refunding fence grounding/bonding is done.


Most company have their own spec on this.

You likely won’t find anything regarding this in the NEC to satisfy a gas company standard for fence grounding/bonding.

I believe the NEC only hits on likely to become energized and fencing around overhead conductors/substation work.

Correct me if I’m wrong

Maybe try IEEE green book

As far as I can tell you are right about what the NEC talks about, I will look into that resource, thank you

 

[JWall886]

I know the fence around a cell tower has to be bonded.

Likely the company came up with the 20ft number basis to maintain a consistent gradient along the perimeter of the fence given your typical soil conditions.
This number could be adjusted up or down with ground resistance testing for the specific conditions at the location if you really want to get that involved.

2026 NFPA-780 has some information for fences grounding and bonding in article

4.15.5 * Metallic Fences.​

and the appendix A.4.15.5

Thank you, I will look into this to try and get a better idea

 

[JWall886]

Isn't the fence already grounded? Or are the posts mounted on plastic piles of some sort?

Yeah, this is why I say this fence doesn't need to be grounded outside of anything but company policy but that's not something I am willing to attempt to push through; it is inherently safer being grounded in the extremely minute chance someone is touching the fence when lighting strikes it which is the only reasonable thing to expect that could happen. I'm just looking for something to say, "we can ground at this distance instead of 20ft"

 

[electrofelon]

Years ago we had a long tractor trailer scale a few feet from a several hundred foot long 8' high fence. Several times a year at least one to all four load cells would burn out after storms..Tech who replaced the load cells & serviced the scale recommended that we Install a ground rod at each end of fence nearest two ends of k scale. Fence post were set into maybe 2' of concrete. Anyway we installed ground rods and ran a #6 copper wire from first ground rod to holes drilled & tapped in every steel fence post along scale. Until p!ace closed down a few years later no load cells burned out.

I can't tell you how many times I have heard "we added some ground rods and haven't had a problem since"

 

[garbo]

Thank you, I will look into this to try and get a better idea

Problem that I came across with ground resistance II that no having an expensive ground resistance reading meter or whatever they are called is that a few times I could get a 100 watt 120 volt incandescent light bulb to produce a dim light in the summer but nothing in middle of winter when it was 30 degrees F. Removed the wire from ground rod and used a non GFCI receptacle to supply up the energized ( ya hot wire ). Mike Holt did a great video where he had to screw together ground rods and finally after 40' into the ground in his bug open back yard wss finally able to get just under 25 ohms ground resistance. I hammered in my share of 8' long 5/8" diameter ground rods and donuts want to think about driving any ride deeper then 8'. Did work for an old Ma Bell installer. He Saud they had ground rods out in the country side that every winter the resistance went up so much they were told to dig a 12 " circle around ground rid and install some type of mineral then water it. Told me mot guys too the short cut and peed on ground rod.

 

[readydave8]

Saud

If that was voice to text, what is your accent?

Or autocorrect?

Just curious

 

[Joethemechanic]

Problem that I came across with ground resistance II that no having an expensive ground resistance reading meter or whatever they are called is that a few times I could get a 100 watt 120 volt incandescent light bulb to produce a dim light in the summer but nothing in middle of winter when it was 30 degrees F. Removed the wire from ground rod and used a non GFCI receptacle to supply up the energized ( ya hot wire ). Mike Holt did a great video where he had to screw together ground rods and finally after 40' into the ground in his bug open back yard wss finally able to get just under 25 ohms ground resistance. I hammered in my share of 8' long 5/8" diameter ground rods and donuts want to think about driving any ride deeper then 8'. Did work for an old Ma Bell installer. He Saud they had ground rods out in the country side that every winter the resistance went up so much they were told to dig a 12 " circle around ground rid and install some type of mineral then water it. Told me mot guys too the short cut and peed on ground rod.

Salt lowers the impedance of a ground rod a whole lot. I read that in a book from like 1910 and tested it and believe me it works.

 

[Joethemechanic]

Problem that I came across with ground resistance II that no having an expensive ground resistance reading meter or whatever they are called is that a few times I could get a 100 watt 120 volt incandescent light bulb to produce a dim light in the summer but nothing in middle of winter when it was 30 degrees F. Removed the wire from ground rod and used a non GFCI receptacle to supply up the energized ( ya hot wire ). Mike Holt did a great video where he had to screw together ground rods and finally after 40' into the ground in his bug open back yard wss finally able to get just under 25 ohms ground resistance. I hammered in my share of 8' long 5/8" diameter ground rods and donuts want to think about driving any ride deeper then 8'. Did work for an old Ma Bell installer. He Saud they had ground rods out in the country side that every winter the resistance went up so much they were told to dig a 12 " circle around ground rid and install some type of mineral then water it. Told me mot guys too the short cut and peed on ground rod.

Chemical Ground Electrode​

Chemical ground electrodes provide a low impedance ground in locations of high soil resistivity and dry soil conditions. Used in conjunction with a bentonite backfill and nVent ERICO’s unique GEM material, the nVent ERICO chemical ground rod electrode systems provide a method to improve soil resistivity directly surrounding the electrode, and can replace multiple conventional ground rods. It maintains a low ground resistance, that dissipates lightning energy and other dangerous electrical fault currents, even in sandy or rocky soil conditions.
The chemical ground electrode is useful for providing an effective earth in poor soil conditions where space for electrodes is limited. Applications include telecommunications, power generation and distribution, commercial and industrial, manufacturing, transportation (rail and aviation), lightning protection, recreational facilities, and defense. The nVent ERICO chemical ground rod electrode systems are most effective when installed as part of a total system that includes high conductivity backfill materials, access/inspection wells, and permanent, reliable nVent ERICO Cadweld connections. They may be installed either vertically or horizontally.

Chemical Ground Electrode Salt Mix​

Catalog Number Unit Weight
ECRCHM15LB 15 lb

Chemical Ground Electrodes

Chemical Ground Electrodes | Ground Rods

www.nvent.com

The ground electrode salt mixwill work with a regular ground rod also.

When i tested what it said in the book, I just dug a little bit out around the ground rod and filled it with regular rock salt. I tested it with a 120 volt hot and an ammeter. Made a big difference. It was grounding for a 160 Meter ham radio antenna I built.

 

[garbo]

View attachment 2579640

Chemical Ground Electrode​

Chemical ground electrodes provide a low impedance ground in locations of high soil resistivity and dry soil conditions. Used in conjunction with a bentonite backfill and nVent ERICO’s unique GEM material, the nVent ERICO chemical ground rod electrode systems provide a method to improve soil resistivity directly surrounding the electrode, and can replace multiple conventional ground rods. It maintains a low ground resistance, that dissipates lightning energy and other dangerous electrical fault currents, even in sandy or rocky soil conditions.
The chemical ground electrode is useful for providing an effective earth in poor soil conditions where space for electrodes is limited. Applications include telecommunications, power generation and distribution, commercial and industrial, manufacturing, transportation (rail and aviation), lightning protection, recreational facilities, and defense. The nVent ERICO chemical ground rod electrode systems are most effective when installed as part of a total system that includes high conductivity backfill materials, access/inspection wells, and permanent, reliable nVent ERICO Cadweld connections. They may be installed either vertically or horizontally.

View attachment 2579642

Chemical Ground Electrode Salt Mix​

Catalog Number Unit Weight
ECRCHM15LB 15 lb

Chemical Ground Electrodes

Chemical Ground Electrodes | Ground Rods

www.nvent.com

The ground electrode salt mixwill work with a regular ground rod also.

When i tested what it said in the book, I just dug a little bit out around the ground rod and filled it with regular rock salt. I tested it with a 120 volt hot and an ammeter. Made a big difference. It was grounding for a 160 Meter ham radio antenna I built.

Thanks. First time seeing one.Curious how chemicals &/or salt affects the life of typical copper colored plated ground rods. One of the machine shops that I did work for were talked into driving a ground rod next to every CNC & EDM machines. Shop was clean & air conditioned. About 8 years after they moved in they added onto the building and moved every machine. They made a heavy two piece 1" wide steel clamp to pull ground rods out if the ground with a fork.lift. Some were so corroded they broke off after a few feet were raised out of the floor. The few that were able to be pulled out of the floor were corroded & pitted with missing outer jscket.That shop was built on Virgin ground where only trees & grass were.Convinced them they did not need ground rods in any equipment. Pulled a copper ground wire to each machine. My thinking was that building had a low resistance ground path due to 1" copper water service and to a lesser extent with cast iron waste and steel underground gas service ( not sure if had dielectric union ). Did drive in a second ground rod for the single & there phase services..

 

[Joethemechanic]

Curious how chemicals &/or salt affects the life of typical copper colored plated ground rods.

Yeah I wondered the same thing, I can't imagine it being good. The ones I put in for my antennas were some heavy wall copper pipe that I picked out of the scrap. They were only in for about 5 or 6 years and then I sold the property and was too busy at the time to pull them out.

The only ones I saw in real life other than my homemade ones were at an old AM radio tower site and not sure if they were for something to do with lightening protection. Usually those towers have radial grounds buried that are just as long as the tower is high. The base of the tower is mounted on insulators and the whole tower is the radiating element. Those ones could have been for anything, there wasn't much left on the site to go by