Hello. As I understand it, a UFER ground is superior to 2 ground rods. Is it possible/effective to use basement walls w/rebar instead of footings to create a UFER? I think this method would be superior to using the footings because there is more rebar tied together and more concrete surface area in contact with the earth when compared to the the rebar and surface area of footings. It would/will be great to hear 2-3 comments w/code references and a little theory to convince me. Thanks to all that take the time.
UFER characteristics?
- Thread starter sarg1
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- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: UFER characteristics?
A concrete encased electrode must comply with the rules in 250.52(A)(3). These rules were based on the orginal research by h Ufer in the early 1960's, basically the rebar needs to be in the footing to be in contact with weter soil.
But if the wall rebar is tied to the footing rebar, with tie wires, then you have met the requrements.
A concrete encased electrode must comply with the rules in 250.52(A)(3). These rules were based on the orginal research by h Ufer in the early 1960's, basically the rebar needs to be in the footing to be in contact with weter soil.
But if the wall rebar is tied to the footing rebar, with tie wires, then you have met the requrements.
bphgravity
Senior Member
- Location
- Florida
Re: UFER characteristics?
Superior in context to what? If your talking about overall impedance of the grounding system, then yes. However, I do not believe there is any evidence a concrete-encased electrode is any safer or is any better at providing the requirements of 250.4(A)(1) simply becasue of the lower resistance.
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
Re: UFER characteristics?
In Cheyenne, WY, they've actually banned ground rods, because the ground is so stinkin' hard (and the wind always blows, and the refinery is in the middle of town, and it stinks, and...oh...anyway) that everybody was driving ground rods a foot and chopping them. Now UF'er is the secondary ground in houses, period.
Just a pearl of insight. Glad I could help.
In Cheyenne, WY, they've actually banned ground rods, because the ground is so stinkin' hard (and the wind always blows, and the refinery is in the middle of town, and it stinks, and...oh...anyway) that everybody was driving ground rods a foot and chopping them. Now UF'er is the secondary ground in houses, period.
Just a pearl of insight. Glad I could help.
bphgravity
Senior Member
- Location
- Florida
Re: UFER characteristics?
Build three structures next to each other and install a typical electrical service to each. For the first structure, a concrete-encased electrode is used with a measured resistance of 6-ohms. The second structure gets a single ground rod measured at 250-ohms. The third structures has no grounding eloectrode system.
Monitor the three systems for 10 years using a double blind method. I would be willing to bet that a trained professional would not be able to match the data with each structure.
Basically, there would be no discernible difference in the operation or safety of each system.
Don't get me wrong. I am a consumer advocate. I proposed expaned use of GFCI, AFCI, and even voltage drop requirements for the 2005 NEC. There are many better ways the purpose of our code can be met without adding more conservative grounding methods.
Build three structures next to each other and install a typical electrical service to each. For the first structure, a concrete-encased electrode is used with a measured resistance of 6-ohms. The second structure gets a single ground rod measured at 250-ohms. The third structures has no grounding eloectrode system.
Monitor the three systems for 10 years using a double blind method. I would be willing to bet that a trained professional would not be able to match the data with each structure.
Basically, there would be no discernible difference in the operation or safety of each system.
Don't get me wrong. I am a consumer advocate. I proposed expaned use of GFCI, AFCI, and even voltage drop requirements for the 2005 NEC. There are many better ways the purpose of our code can be met without adding more conservative grounding methods.
charlie
Senior Member
- Location
- Indianapolis
Re: UFER characteristics?
, I hope there is no lightning of we have no transformer failures during that time.
Bennie . . . UH . . . Bryan
, I hope there is no lightning of we have no transformer failures during that time. bphgravity
Senior Member
- Location
- Florida
Re: UFER characteristics?
Confusing my statements for Bennie's is an honor. (For the most part)
Confusing my statements for Bennie's is an honor. (For the most part)
Re: UFER characteristics?
In the bottom slab I would use Ufer's method of grounding:
"The concrete encased electrode shall consist of at least 20 feet of bare copper not smaller than No. 4 AWG encased in 2 inches of concrete near the bottom of the footing or foundation."
Appendix page 234, IAEI Soares Book on Grounding
And if copper pipe is used in the plumbing, don't forget to bond the hot and cold water pipes together at the water heater (this system is also to be bonded to the main grounding electrode system sizing in accordance with 1996 NEC Table 250-94, Section 250-81). And, if you really want to be ahead of the curve, bond the hot and cold water pipes at each mixer at the tub and/or shower stalls. "Likely to become energized" are key words to take to heart when thinking about the safety of others. And no amount of money spent now can compare to the piece of mind that what you install is the absolute safest possible.
http://www.ul.com/regulators/ode/0203.pdf
"Generally, Section 250.104(A) requires all metal water-piping systems installed in or attached to a building or structure to be bonded to the electrical service equipment enclosure, to the grounded conductor at the service, the grounding electrode conductor, where it is large enough, or to one of the grounding electrodes at the building. The bonding jumper from the service to the water-piping system must be sized in accordance with Section 250.66 and Table 250.66. This bonding jumper is sized using the same section and table used for the grounding-electrode conductor for the service."
"Most electricians automatically bond the cold water line but do not ensure that the cold and the hot water lines are metallically interconnected through mixing valves in the plumbing fixtures. Since Section 250.104(A) requires all water-piping systems to be bonded back to the service, and hot or cold water linesare not specifically mentioned, both hot and cold water lines must be bonded and connected back to the building service. The bonding jumper from the cold to the hot water piping system must be sized in accordance with Section and Table 250.66."
http://www.sea.siemens.com/step/pdfs/surge_2.pdf
http://www.rbs2.com/pq.htm
"There are a number of other "power quality" problems, such as distortion of the sinusoidal voltage waveform, disturbances of the rms voltage (e.g., brownouts, temporary overvoltages), etc. The solution to these problems is to use appropriate technology, such as line conditioners. I put the term "power quality" inside quotation marks, because it is a misnomer: the real problem is with disturbances in the voltage waveform, not power. Nevertheless, "power quality" has become a common term among engineers and technicians who work with delivery of electrical power to customers."
http://www.rbs2.com/blitz.htm
[ December 05, 2004, 02:40 PM: Message edited by: rannon ]
The rebar used in most of the basement construction I have seen doesn't tie the two slabs (vertical and horizontal) together. Rather, they have a keyway joint constructed between the two allowing a type of interlocking joint for layout purposes or sealing. A cold joint does not meet the requirements for a Ufer Ground. As far as the bottom slab rebar may qualify, but paralleling ground rods would be a better method of providing adequate acceptable grounding. The Ufer provided with the bottom slab of the basement would simply augment the paralleled ground rods and/or cold water ground/bonding thus eliminating a potential difference within the basement. If it were my house I would create a bonding ring around the house bonding all of the vertical slabs together with a #2 bare copper tied to a #4 bare copper which is bonded to the rebar of each individual slabs (including the bottom slab).
In the bottom slab I would use Ufer's method of grounding:
"The concrete encased electrode shall consist of at least 20 feet of bare copper not smaller than No. 4 AWG encased in 2 inches of concrete near the bottom of the footing or foundation."
Appendix page 234, IAEI Soares Book on Grounding
And if copper pipe is used in the plumbing, don't forget to bond the hot and cold water pipes together at the water heater (this system is also to be bonded to the main grounding electrode system sizing in accordance with 1996 NEC Table 250-94, Section 250-81). And, if you really want to be ahead of the curve, bond the hot and cold water pipes at each mixer at the tub and/or shower stalls. "Likely to become energized" are key words to take to heart when thinking about the safety of others. And no amount of money spent now can compare to the piece of mind that what you install is the absolute safest possible.
http://www.ul.com/regulators/ode/0203.pdf
"Generally, Section 250.104(A) requires all metal water-piping systems installed in or attached to a building or structure to be bonded to the electrical service equipment enclosure, to the grounded conductor at the service, the grounding electrode conductor, where it is large enough, or to one of the grounding electrodes at the building. The bonding jumper from the service to the water-piping system must be sized in accordance with Section 250.66 and Table 250.66. This bonding jumper is sized using the same section and table used for the grounding-electrode conductor for the service."
"Most electricians automatically bond the cold water line but do not ensure that the cold and the hot water lines are metallically interconnected through mixing valves in the plumbing fixtures. Since Section 250.104(A) requires all water-piping systems to be bonded back to the service, and hot or cold water linesare not specifically mentioned, both hot and cold water lines must be bonded and connected back to the building service. The bonding jumper from the cold to the hot water piping system must be sized in accordance with Section and Table 250.66."
http://www.sea.siemens.com/step/pdfs/surge_2.pdf
http://www.rbs2.com/pq.htm
"There are a number of other "power quality" problems, such as distortion of the sinusoidal voltage waveform, disturbances of the rms voltage (e.g., brownouts, temporary overvoltages), etc. The solution to these problems is to use appropriate technology, such as line conditioners. I put the term "power quality" inside quotation marks, because it is a misnomer: the real problem is with disturbances in the voltage waveform, not power. Nevertheless, "power quality" has become a common term among engineers and technicians who work with delivery of electrical power to customers."
http://www.rbs2.com/blitz.htm
[ December 05, 2004, 02:40 PM: Message edited by: rannon ]
- Location
- Massachusetts
Re: UFER characteristics?
IMO that is a bit over the top for a dwelling unit.
Hit the rebar in the footing and forget about it.
Are you running a communication site out of your house?
IMO that is a bit over the top for a dwelling unit.
Hit the rebar in the footing and forget about it.
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