Grounding rod-Structural Engineer letter
Grounding rod-Structural Engineer letter
(OP)
Now a days, most of the city asking a letter after re-bar inspection is done by Engineer. It's not that difficult to issue a letter based on what we observed.
But it makes difficult when city wants Structural engineer add a line " Concrete earth electrode is provided as per NEC 20xx" in the letter. As a structural engineer I have no knowledge about NEC (national Electrical code)so I can't certify that. General contractor is not getting a green tag without engineer letter. They also don't want to hire Electrical engineer for another inspection.
City prospector inspected and gave "okay" but wants letter !!!!!!!What's the best way to tackle this issue. Any suggestion would be appreciated. Thank you
Note: For residential, city doesn't requires a electrical engineer to design electrical. 99% cases Electrical is done(layout) by Architect who provides information based on common practice. GC hires a certified electrician to do the job.
I don't understand why a letter by a PE needed when there is no Electrical engineer is involved!!!!!!!!!
But it makes difficult when city wants Structural engineer add a line " Concrete earth electrode is provided as per NEC 20xx" in the letter. As a structural engineer I have no knowledge about NEC (national Electrical code)so I can't certify that. General contractor is not getting a green tag without engineer letter. They also don't want to hire Electrical engineer for another inspection.
City prospector inspected and gave "okay" but wants letter !!!!!!!What's the best way to tackle this issue. Any suggestion would be appreciated. Thank you
Note: For residential, city doesn't requires a electrical engineer to design electrical. 99% cases Electrical is done(layout) by Architect who provides information based on common practice. GC hires a certified electrician to do the job.
I don't understand why a letter by a PE needed when there is no Electrical engineer is involved!!!!!!!!!






RE: Grounding rod-Structural Engineer letter
BA
RE: Grounding rod-Structural Engineer letter
Tell the inspector that what he is requiring is contrary to state law and not allowed. If he must have an electrical certification, then he needs to get it from an electrical contractor (for residential) or an electrical engineer (all else).
RE: Grounding rod-Structural Engineer letter
Copied from:
https://www.thebuildingcodeforum.com/forum/threads...
"It should be noted that the "piece of rebar" should be tied to at least 20 feet of rebar or #4 copper that is encased in concrete, and the concrete is supposed to be in direct contact with the earth. And this means that if there is a vapor barrier between the concrete and the gravel, that is no good."
Additional links:
http://electricalcodeconnection.com/250-52-a3-conc...
https://www.google.com/url?sa=t&rct=j&q=&a...
"Engineering is achieving function while avoiding failure." - Henry Petroski
RE: Grounding rod-Structural Engineer letter
1) The concrete must make electrical contact with the earth, i.e. cannot be separated by vapor barrier, so it is the responsibility of the electrical inspector.
2) A structural inspection of the re-bar may be done prior to pouring concrete, so the inspector may not see the concrete portion of the grounding, nor should he be expected to be on hand when it is poured.
BA
RE: Grounding rod-Structural Engineer letter
RE: Grounding rod-Structural Engineer letter
Dave
Thaidavid
RE: Grounding rod-Structural Engineer letter
RE: Grounding rod-Structural Engineer letter
I wasn't aware of that restriction in some jurisdictions. We've prepared numerous project drawings with cadwelds to structural steel, chain link fences, SOG reinforcing, pad reinforcing, friction piles, etc. for switchyards, transformer yards, etc. Also show pads and plates for NEMA 2 fasteners.
Dik
RE: Grounding rod-Structural Engineer letter
We would usually attach the slab rebar to the home's ground circuit (see attached diagram). The electricians always said it was the dumbest idea in the world and would often instruct the homeowners how to disconnect after closing. What happens if you are barefoot in the garage or in the shower and your house gets hit by lightening? I don't know the correct answer but it doesn't seem like a real good idea to me. If a large amount of charge goes into the slab and the slab is wrapped in plastic, then how does it get out?
Would the permitting office accept a letter from a licensed electrician? Or maybe you could add a plan comment along the lines of "electrical contractor to provide slab grounding connection pursuant to electrical code section xxxx and any other applicable requirements"
RE: Grounding rod-Structural Engineer letter
Ground rods, metal plates.
By such means, the rebar is just rebar. Nothing to do with grounding.
RE: Grounding rod-Structural Engineer letter
RE: Grounding rod-Structural Engineer letter
RE: Grounding rod-Structural Engineer letter
Dik
RE: Grounding rod-Structural Engineer letter
I consider the doping of the soil and the resulting rise in conductivity to more important than the change from the original copper to steel.
And
Construction
Concrete is naturally basic (has high pH). Ufer observed this meant that it had a ready supply of ions and so provides a better electrical ground than almost any type of soil. Ufer also found that the soil around the concrete became "doped", and its subsequent rise in pH caused the overall impedance of the soil itself to be reduced.[3] The concrete enclosure also increases the surface area of the connection between the grounding conductor and the surrounding soil, which also helps to reduce the overall impedance of the connection.
Ufer's original grounding scheme used copper encased in concrete. However, the high pH of concrete often causes the copper to chip and flake. For this reason, steel is often used instead of copper.
When homes are built on concrete slabs, it is common practice to bring one end of the rebar up out of the concrete at a convenient location to make an easy connection point for the grounding electrode.[4]
Ufer grounds, when present, are preferred over the use of grounding rods. In some areas (like Des Moines, Iowa) Ufer grounds are required for all residential and commercial buildings.[5] The conductivity of the soil usually determines if Ufer grounds are required in any particular area.
An Ufer ground of specified minimum dimensions is recognized by the U.S. National Electrical Code as a grounding electrode.[6] The grounding conductors must have sufficient cover by the concrete to prevent damage when dissipating high-current lightning strikes.[7]
Bill
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"Why not the best?"
Jimmy Carter
RE: Grounding rod-Structural Engineer letter
RE: Grounding rod-Structural Engineer letter
Would they require a Electrical PE to certify the rebar is structurally adequate for the foundation? Same deal. Maybe put that in your letter.
RE: Grounding rod-Structural Engineer letter
We just throw in a couple of ground rods so he has something to see. NEC never requires more than two ground rods even though they may not have low enough resistance. Rebar embedded in concrete at the lowest level (no vapor barrier) will probably be the best ground around. However, if it is new construction, anything that can be used as a grounding electrode, that is present, must be utilized. We put ground rods in only to satisfy the local inspectors so he can 'see' something.
RE: Grounding rod-Structural Engineer letter
It might be that what is being asked for is a letter from a licensed electrician regarding the grounding connections. Have a conversation with the inspector about what is being asked for.
RE: Grounding rod-Structural Engineer letter
the design has to be the result of collaboration between an electrical engineer and a structural one, but the execution inspection has to be done by a building inspector and a legal record of this inspection has to presented for approval.
A field inspection of this installation by a building inspector does not require any specialized training. See-for instance:
http://www.nj.gov/dca/divisions/codes/publications...