ground rods
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GG
Senior Member
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- Ft.Worth, T.X.
Re: ground rods
Zero if you have a cold water ground and go to the rebar in the footing.
[ July 17, 2005, 11:32 PM: Message edited by: GG ]
Zero if you have a cold water ground and go to the rebar in the footing.
[ July 17, 2005, 11:32 PM: Message edited by: GG ]
macmikeman
Senior Member
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- Planet macmikeman
Re: ground rods
Not exactly, what it does require is that if you are using ground rod as a supplemental electrode it must present no more than 25 ohms of resistance which is not so easy to prove. You would need to perform a ground rod test to show it does not have a higher resistance. So therefore it is usually much easier to just get the second rod in and be done with it. See 250.56 for reference. P.S. Inspectors where I am at have never asked me for rod #2 yet, except for in cases where the plumbers used plastic wrap over the buried copper water pipes.
Not exactly, what it does require is that if you are using ground rod as a supplemental electrode it must present no more than 25 ohms of resistance which is not so easy to prove. You would need to perform a ground rod test to show it does not have a higher resistance. So therefore it is usually much easier to just get the second rod in and be done with it. See 250.56 for reference. P.S. Inspectors where I am at have never asked me for rod #2 yet, except for in cases where the plumbers used plastic wrap over the buried copper water pipes.
macmikeman
Senior Member
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- Planet macmikeman
Re: ground rods
Whoops, GG my "not exactly" reply was to the original poster, you were faster than me in getting the answer back.
Whoops, GG my "not exactly" reply was to the original poster, you were faster than me in getting the answer back.
GG
Senior Member
- Location
- Ft.Worth, T.X.
Re: ground rods
No problem macmikeman. Where I live the utility wont put a meter in unless they see a ground rod anyway so your post would be the norm here. Plus like you I haven't had an inspector have me drive a 2nd rod or show proof of 25 ohms.
No problem macmikeman. Where I live the utility wont put a meter in unless they see a ground rod anyway so your post would be the norm here. Plus like you I haven't had an inspector have me drive a 2nd rod or show proof of 25 ohms.
allenwayne
Senior Member
Re: ground rods
It amazes me how in different areas different requirements are used.Here we work in 4 different jurisdictions.But have four different requirements.
Area 1-just a footer bond unless water is CU then it has to be used also.
Area 2-2 ground rods and water if CU.
Area 3-1 ground rod with a footer bond and water if CU.
Area 4-has just started using footer bonds.but for the slabs poured before the required uffer we had to chip into a poured up lift cell find rebar attach to it and then hit 2 ground rods and water if CU,I never understood having to chip into an uplift cell in a block wall since that piece is only about 6 ft long and tied to 20 ft of rebar that is in the slab.
Our biggest problem has been theft of copper when slabs have been poured,usually they leave a piece that is around a foot long
It amazes me how in different areas different requirements are used.Here we work in 4 different jurisdictions.But have four different requirements.
Area 1-just a footer bond unless water is CU then it has to be used also.
Area 2-2 ground rods and water if CU.
Area 3-1 ground rod with a footer bond and water if CU.
Area 4-has just started using footer bonds.but for the slabs poured before the required uffer we had to chip into a poured up lift cell find rebar attach to it and then hit 2 ground rods and water if CU,I never understood having to chip into an uplift cell in a block wall since that piece is only about 6 ft long and tied to 20 ft of rebar that is in the slab.
Our biggest problem has been theft of copper when slabs have been poured,usually they leave a piece that is around a foot long
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- Windsor, CO NEC: 2017
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- Service Manager
Re: ground rods
charlie
Senior Member
- Location
- Indianapolis
Re: ground rods
Maybe if people would just get some education . . .
Maybe if people would just get some education . . .
Re: ground rods
If underground water pipe is used as the grounding electrode system it must have a supplemental electrode 250.53(D)(2). I believe the reason is that if the underground water pipe is ever replaced it will be changed to plastic. So it is important that if a ground rod is used to supplement
the water pipe it must meet the 25 ohm requirement or a second ground rod must be used, and it must be at least 6ft. from the first.
Inspectors that are allowing 1 ground rod are not doing there job, and should have a hard time sleeping at night. romeo
If underground water pipe is used as the grounding electrode system it must have a supplemental electrode 250.53(D)(2). I believe the reason is that if the underground water pipe is ever replaced it will be changed to plastic. So it is important that if a ground rod is used to supplement
the water pipe it must meet the 25 ohm requirement or a second ground rod must be used, and it must be at least 6ft. from the first.
Inspectors that are allowing 1 ground rod are not doing there job, and should have a hard time sleeping at night. romeo
charlie
Senior Member
- Location
- Indianapolis
Re: ground rods
I can't agree with that statement. It depends on the area's soil conditions. If it is normal to get 15 Ω in a subdivision and homes are going in the same area, why require two rods? Some people do measure their ground resistance.
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: ground rods
[ July 18, 2005, 10:05 PM: Message edited by: ryan_618 ]
Actually, I sleep very well, and I only require one, if any!
[ July 18, 2005, 10:05 PM: Message edited by: ryan_618 ]
charlie
Senior Member
- Location
- Indianapolis
Re: ground rods
Ryan, the quote was made by Romeo, not me. The way you posted the quote, it looks like I made it instead of Romeo.
Ryan, the quote was made by Romeo, not me. The way you posted the quote, it looks like I made it instead of Romeo.
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: ground rods
Originally posted by charlie:
Ryan, the quote was made by Romeo, not me. The way you posted the quote, it looks like I made it instead of Romeo.
Re: ground rods
In some areas the general experience is that the soil is so poor that they just flat require 2 rods if you are using them. Some areas that flat require 2 rods if you are using them:
1. West Penn Power in PA
2. New York State
3. Geauga County, Ohio
Actually, New York State requires that you also use #4 solid copper to hook up the ground wires. It must run unbroken from the service ground bus to the first rod, loop unspliced through the clamp and then to the second rod, run unspliced through the second rod clamp, and then back to the service using a different physical path. Any trench or protective conduit cannot be shared by the 2 segments that are connected to the ground bus in the service switch. This is so that if the GEC is ever cut, you still have 2 rods.
The mechanical protection requirement in NEC 250.64(B) can also dictate that the GEC for a ground rod be #4 copper. Some places such as Akron, Ohio do not allow a GEC smaller than #4 solid or #2 stranded copper because they do not want to take time to determine if #6 copper is protected enough. The #6 copper wire rule for a plate or rod electrode is 150 year old rule from when telegraph systems were wired with #6 steel wire.
In some areas the general experience is that the soil is so poor that they just flat require 2 rods if you are using them. Some areas that flat require 2 rods if you are using them:
1. West Penn Power in PA
2. New York State
3. Geauga County, Ohio
Actually, New York State requires that you also use #4 solid copper to hook up the ground wires. It must run unbroken from the service ground bus to the first rod, loop unspliced through the clamp and then to the second rod, run unspliced through the second rod clamp, and then back to the service using a different physical path. Any trench or protective conduit cannot be shared by the 2 segments that are connected to the ground bus in the service switch. This is so that if the GEC is ever cut, you still have 2 rods.
The mechanical protection requirement in NEC 250.64(B) can also dictate that the GEC for a ground rod be #4 copper. Some places such as Akron, Ohio do not allow a GEC smaller than #4 solid or #2 stranded copper because they do not want to take time to determine if #6 copper is protected enough. The #6 copper wire rule for a plate or rod electrode is 150 year old rule from when telegraph systems were wired with #6 steel wire.
Re: ground rods
Romeo, worrying about what may happen in the future is not a justification for requiring over and above what your adopted codes are.
What would you do if there is a piece of equipment calling for a 125 amp fused protection, it is fed with 125 amp conductors and protected with 125 amp fuses in a 200 amp fusible switch, would you require this be changed somehow due to the fact that some time in the future someone may put larger fuses in?
We simply can not control the "What Ifs"
On another note, even if these rods combined got down to 5 ohms total resistance they aren't doing much anyways, I call them placebos.
Roger
[ July 19, 2005, 07:42 AM: Message edited by: roger ]
Romeo, worrying about what may happen in the future is not a justification for requiring over and above what your adopted codes are.
What would you do if there is a piece of equipment calling for a 125 amp fused protection, it is fed with 125 amp conductors and protected with 125 amp fuses in a 200 amp fusible switch, would you require this be changed somehow due to the fact that some time in the future someone may put larger fuses in?
We simply can not control the "What Ifs"
On another note, even if these rods combined got down to 5 ohms total resistance they aren't doing much anyways, I call them placebos.
Roger
[ July 19, 2005, 07:42 AM: Message edited by: roger ]
Re: ground rods
Roger Supplemental electrodes for a underground metal water pipes is not over and above NEC requirements it is required by section 250.53(C)(2). Also I would not require a change for the 125A. circuit you mention because it is not a violation.
romeo
P.S. I am not trying to start an issue here just gave IMO . Thanks
Roger Supplemental electrodes for a underground metal water pipes is not over and above NEC requirements it is required by section 250.53(C)(2). Also I would not require a change for the 125A. circuit you mention because it is not a violation.
romeo
P.S. I am not trying to start an issue here just gave IMO . Thanks
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: ground rods
I just don't get that excited about ground resistance.
Ya know, it's funny. The main function of the grounding electrode system is for lightning protection. The NFPA 780 (lightning protection) says to drive two 10 foot ground rods and call it a day. Why do we have to have ufer's and water pipes and building steel and ground rods and everything else?
I just don't get that excited about ground resistance.
Ya know, it's funny. The main function of the grounding electrode system is for lightning protection. The NFPA 780 (lightning protection) says to drive two 10 foot ground rods and call it a day. Why do we have to have ufer's and water pipes and building steel and ground rods and everything else?
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