Resistance to Ground
- Thread starter cjcrawfo
- Start date
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friebel
Senior Member
- Location
- Pennsville, N.J.
Re: Resistance to Ground
To: cjcrawfo, Your question is, "how to get your ground resistance down to 5 ohms or less".
I worked for a large chemical company and there were times that we would need to get our ground resistance down to 5 ohms. This is how we would do it.
1. We would start with the Ufer ground system.
2. Then we would generally have a water main coming into the building of at least a 6 inch main. We would tie into the water line with our ground before the first valve.
3. After doing number 1, and 2, we generally had the ohm reading that we wanted, but there was one time that we also drove a ground rods 50 feet into the earth before we could achieve the 5 ohm reading that we desired.
All of the above grounds were tied togeather, for our main ground system. We did not separate them, like some of the instrument people would want us to do. I hope that this will help you out with your grounding problem.
To: cjcrawfo, Your question is, "how to get your ground resistance down to 5 ohms or less".
I worked for a large chemical company and there were times that we would need to get our ground resistance down to 5 ohms. This is how we would do it.
1. We would start with the Ufer ground system.
2. Then we would generally have a water main coming into the building of at least a 6 inch main. We would tie into the water line with our ground before the first valve.
3. After doing number 1, and 2, we generally had the ohm reading that we wanted, but there was one time that we also drove a ground rods 50 feet into the earth before we could achieve the 5 ohm reading that we desired.
All of the above grounds were tied togeather, for our main ground system. We did not separate them, like some of the instrument people would want us to do. I hope that this will help you out with your grounding problem.
Re: Resistance to Ground
Thanks for the response all but we already tried getting a professional company that only did grounding and they quoted us almost 18K and they wouldn't gurantee the 5 ohm. As far as bonding to water pipes were are not allowed to b/c our system has to stand alone and there aren't any pipe where we are working at.
Thanks for the response all but we already tried getting a professional company that only did grounding and they quoted us almost 18K and they wouldn't gurantee the 5 ohm. As far as bonding to water pipes were are not allowed to b/c our system has to stand alone and there aren't any pipe where we are working at.
- Location
- Illinois
- Occupation
- retired electrician
Re: Resistance to Ground
cjcrawfo,
Can I ask why you must have 5 or less ohms to earth?
Don
cjcrawfo,
Can I ask why you must have 5 or less ohms to earth?
Don
wanderer20001us
Senior Member
Re: Resistance to Ground
These are expensive but may get the results you are looking for.
http://www.erico.com/products/ChemRod.asp
These are expensive but may get the results you are looking for.
http://www.erico.com/products/ChemRod.asp
Re: Resistance to Ground
Don,
I find myself asking that same question as to WHY? It is a spec for each of our cell sites. The ground here in East TN is nothing but red clay and rock. I was out this morning and megged each of my sites and they all are down. I think the Terra-fill is starting to have some effect.
Sam, thanks for the link I will see if the specs on those rods are any different for the ones we are currently using.
I hope that the client just says enough is enough soon. Thanks again everybody!!!
Don,
I find myself asking that same question as to WHY? It is a spec for each of our cell sites. The ground here in East TN is nothing but red clay and rock. I was out this morning and megged each of my sites and they all are down. I think the Terra-fill is starting to have some effect.
Sam, thanks for the link I will see if the specs on those rods are any different for the ones we are currently using.
I hope that the client just says enough is enough soon. Thanks again everybody!!!
- Location
- Illinois
- Occupation
- retired electrician
Re: Resistance to Ground
cjcrawfo,
That does make sense, transmission sites are one of the very few types of installations, where a low ground resistance is actually required for the performance of the system.
Don
cjcrawfo,
That does make sense, transmission sites are one of the very few types of installations, where a low ground resistance is actually required for the performance of the system.
Don
Re: Resistance to Ground
cjcrawfo, The XIT rods you have are just as good or better than Enrico. Both are basically the same product. Lyncole or no one I know of will gaurantee 5-ohms or better due to changing soil conditions, but they will at least tell you what it will take to get to that point without having to guess and trail and error.
Typically I use a Ufer ground supplemented with a ground ring, XIT rods at each corner of the building/tower and at the building entrance, back filled with bentonite clay at all my cell site designs. Occasionally it takes radials in addition to the rings/rods to achieve 5-ohms or better.
Don, the only purpose I know of for low impedance systems at cell sites or any Telco site is lightning and TVSS protection.
cjcrawfo, The XIT rods you have are just as good or better than Enrico. Both are basically the same product. Lyncole or no one I know of will gaurantee 5-ohms or better due to changing soil conditions, but they will at least tell you what it will take to get to that point without having to guess and trail and error.
Typically I use a Ufer ground supplemented with a ground ring, XIT rods at each corner of the building/tower and at the building entrance, back filled with bentonite clay at all my cell site designs. Occasionally it takes radials in addition to the rings/rods to achieve 5-ohms or better.
Don, the only purpose I know of for low impedance systems at cell sites or any Telco site is lightning and TVSS protection.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Resistance to Ground
This is true somewhat. But only at some low frequency broadcast Am or short wave radio stations. Almost all these today use a radial grid buried around tha transmiting tower for the ground plane effect as the whole tower is the antenna. above 50mhz. the ground plays very little in the transmision signal. But as Dereck has pointed out it's mostly for lightning and noise protection.
Re: Resistance to Ground
I saw an article once where somebody having a bad grounding issue went for an 'active' solution... took a 1" diameter copper pipe and put in a bunch of holes... buried the pipe and installed a system that kept it wet with a continuous drip of water... i tried to find the post online but couldn't find it.
I saw an article once where somebody having a bad grounding issue went for an 'active' solution... took a 1" diameter copper pipe and put in a bunch of holes... buried the pipe and installed a system that kept it wet with a continuous drip of water... i tried to find the post online but couldn't find it.
- Location
- Massachusetts
Re: Resistance to Ground
Water can also raise the resistance of electrodes, pure water is not conductive.
Water can also raise the resistance of electrodes, pure water is not conductive.
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