weressl
Esteemed Member
iwire said:
Oh, so whatever else is the "bonding" condutor - that ALSO pokes out of the footing - is corrosion proof? Especially if it is a different material. A Cu/Fe battery.....
Concrete encased electrode
- Thread starter don_resqcapt19
- Start date
- Status
Oh, so whatever else is the "bonding" condutor - that ALSO pokes out of the footing - is corrosion proof? Especially if it is a different material. A Cu/Fe battery.....
- Location
- Massachusetts
weressl said:
Typically they are brought out under the slab.
But regardless I have never seen copper corrode and pop the concrete apart. On the other hand all I have seen rusting re-bar do that plenty of times.
But I will let the inspectors up here in MA know that you feel they are wrong.
weressl
Esteemed Member
iwire said:Typically they are brought out under the slab.
But regardless I have never seen copper corrode and pop the concrete apart. On the other hand all I have seen rusting re-bar do that plenty of times.
But I will let the inspectors up here in MA know that you feel they are wrong.
The argument just defies logic.
Poking a re-bar out of the slab defies logic. In 250.52 A 3 CEE, an electrode
" Encased by at least 2" of concrete" , located "within and near the bottom
of a concrete foundation or footing that is in direct contact with the earth".
I don't see how poking a rebar thru the top of the concrete comes even
remotely close to the discription given in the NEC!!! To me it's the easy way
out of doing the job right because it gets by. But it's the same thing-- Not in
my book, a VW and a FunnyCar are both automobiles but one performs and
the other barely does it's job.
" Encased by at least 2" of concrete" , located "within and near the bottom
of a concrete foundation or footing that is in direct contact with the earth".
I don't see how poking a rebar thru the top of the concrete comes even
remotely close to the discription given in the NEC!!! To me it's the easy way
out of doing the job right because it gets by. But it's the same thing-- Not in
my book, a VW and a FunnyCar are both automobiles but one performs and
the other barely does it's job.
- Location
- Massachusetts
weressl said:
OK, help me out.
Explain how you would bring out a conductor out of the slab?
Inspectorcliff
Senior Member
- Location
- Colorado
Cce
Cce
In some of the Colorado area we allow the following, 20ft of copper in the footer in close proximity of the ground, (it doesn't say it has to be tied to the rebar, we strongly recommend it), re-bar tied together in close proximity to the ground and one of those pieces extended upwards close to the location of the panel. Some B.O. for different counties or towns require that electrode to come up inside the crawler not outside in the normal environment. :roll: Thanks,
Cce
In some of the Colorado area we allow the following, 20ft of copper in the footer in close proximity of the ground, (it doesn't say it has to be tied to the rebar, we strongly recommend it), re-bar tied together in close proximity to the ground and one of those pieces extended upwards close to the location of the panel. Some B.O. for different counties or towns require that electrode to come up inside the crawler not outside in the normal environment. :roll: Thanks,
Inspectorcliff
Senior Member
- Location
- Colorado
not cce/but CEE
not cce/but CEE
da its still early.
not cce/but CEE
da
its still early.
weressl
Esteemed Member
iwire said:
Same way how the rebar is brought out.
In my experience stubbed REBAR is an invitation for corrosion.
Moreover, this grounding method introduces another big problem: galvanic corrosion (which I believe someone already mentioned). While most of these installations avert this danger through the "massive anode" principle, this problem still exists whenever you connect copper and steel.
Another potential issue with REBAR grounding in building slabs (and foundations to a lesser extent) is the water seal that is sometimes installed beneath the foundation. This thick and heavy plastic layer more or less insulates the building from high water tables, but also electrically insulates that slab.
If someone were to just bond to a REBAR in a slab without knowing that REBAR is solidly and securely connected to a footing that extends beneath the water seal (if present), dangers could abound.
The best way we found to connect to the REBAR is through the use of purpose built grounding plates (Burndy, Blackburn and Erico all carry these). These are little more expensive, but worth it in my opinion (over the life of the installation). And the installation of these allows any inspecting body to ensure connectivity because they are clamped and compressed prior to the pouring of any concrete.
Moreover, this grounding method introduces another big problem: galvanic corrosion (which I believe someone already mentioned). While most of these installations avert this danger through the "massive anode" principle, this problem still exists whenever you connect copper and steel.
Another potential issue with REBAR grounding in building slabs (and foundations to a lesser extent) is the water seal that is sometimes installed beneath the foundation. This thick and heavy plastic layer more or less insulates the building from high water tables, but also electrically insulates that slab.
If someone were to just bond to a REBAR in a slab without knowing that REBAR is solidly and securely connected to a footing that extends beneath the water seal (if present), dangers could abound.
The best way we found to connect to the REBAR is through the use of purpose built grounding plates (Burndy, Blackburn and Erico all carry these). These are little more expensive, but worth it in my opinion (over the life of the installation). And the installation of these allows any inspecting body to ensure connectivity because they are clamped and compressed prior to the pouring of any concrete.
- Location
- Massachusetts
weressl said:
Thanks, that was very helpful and informative. :-?
- Location
- Massachusetts
Frenetic said:
All it takes is a drive around New England and you will see examples of that at many Bridges and other concrete structures, as soon as any rebar is exposed the deterioration gets into high gear.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Frenetic said:
If the footing is not in direct contact with the earth then it does not qualify as a CEE.
Frenetic said:
This really shouldn't be an issue if you use the proper fitting to connect the Cu to the steel.
- Location
- Massachusetts
infinity said:
I agree and will point out a slab does not qualify either.
I agree again, normally by job spec we cad weld the copper to the steel.
weressl
Esteemed Member
iwire said:
You may want to talk to structural engineers. The corrosion starts from the INSIDE. Concrete is porous, permiable by water and the various chemicals present in the concrete are readily initiate the corrosion. Where there is another(different) metal present the corrosion is accelerated. Add road-salt and the condition is aggravated. Epoxy coated re-bars are to stave off the corrosion, but only to delay it not to prevent it completely.
You are toushing on the issue why I think that Ufer grounding is NOT a good practice, insuffciently reserched for its long term effects.
- Location
- Massachusetts
weressl said:
Yes, thanks for concrete 101. :wink:
And as I said once the rebar becomes exposed the deterioration kicks in much faster.
So .....if you intentionally leave piece of rebar sticking out.....
I am done on this subject, feel free to keep going.
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
We don't have the corrosion issues here in Colorado that they do out east.
I haven't seen a lot of old Ufers myself, since the teeth came to the requirement so recently. Generally the rebar is stubbed up inside the garage wall in a dwelling, so in that case it is not subject to much moisture from outside. In commercial, it's usually connected to in the concrete, and the GEC is stubbed up indoors near the service or a suitable grounding bar. Since it comes up indoors, it's not subject to much moisture.
I've only read the last few posts, so if I'm missing a greater discussion here, I apologize in advance.
I haven't seen a lot of old Ufers myself, since the teeth came to the requirement so recently. Generally the rebar is stubbed up inside the garage wall in a dwelling, so in that case it is not subject to much moisture from outside. In commercial, it's usually connected to in the concrete, and the GEC is stubbed up indoors near the service or a suitable grounding bar. Since it comes up indoors, it's not subject to much moisture.
I've only read the last few posts, so if I'm missing a greater discussion here, I apologize in advance.
- Status