If you bought a house in the last 15 years or so, you may actually have a building element protruding from the side of your home. In this article, I discuss service grounding connections and what I call the rebar "sticking-out" method as permitted by Section 250.68(C)(3) of the 2017 National Electrical Code (NEC), which reads as follows:
"A rebar type concrete-encased electrode installed in accordance with 250.52(A)(3) with an additional rebar section extended from its location within the concrete to an accessible location that is not subject to corrosion shall be permitted for connection of grounding electrode conductors and bonding jumpers. The rebar extension shall not be exposed to contact with the earth without corrosion protection."
When the steel rebar "sticking-out" method first started to appear, a piece of upturned rebar was tied to the footing steel and many times simply left sticking out from the side of a home. The grounding electrode conductor was then clamped onto this piece of steel to ground the electrical service.
I have seen this method used as early as the 1990s when I worked as an electrical inspector for Pinellas County, Fla. I believe we were one of the first jurisdictions to allow for this surrogate. This stands to reason, as we were one of the first jurisdictions in Florida to mandate the 250.52(A)(3) concrete-encased electrode be utilized. Back at that time, the 250.68 "sticking-out" method was not yet codified, but the various jurisdictions allowed it nevertheless.
For the purposes of this article, it is important to understand that this is not the method that was tested for performance by Herbert G. Ufer, the father of the concrete-encased electrode. Electrical inspectors later discovered that, with the sticking-out method came many problems and issues (or at least we did).
One of the most obvious problems was that of corrosion. Rusting is extremely common with steel reinforcing bar. Even high humidity can cause it to rust. This is especially an issue at the point where the grounding electrode conductor attaches to the reinforcing bar, usually by means of a ground clamp. This turns out to be a weak link if the reinforcing bar is stubbed-up outside the building. If the steel is exposed to the elements, I believe the point at which the ground clamp is attached will need to be protected by some means, but I'm not quite sure what the correct solution would be. Should the protection be some type of encapsulation? An approved potting compound or epoxy? These and other methods may render the connection not completely visible to the electrical inspector, which could be a big problem.
Corrosion at the point of connection for the grounding electrode conductor—in reference to the below-grade portion of the upturned reinforcing bar—is also a significant issue. More often than not, the contractor will leave the upturned rebar sticking out of the foundation, below grade. We can all agree that steel reinforcing bar is subject to extreme corrosion when routed below the earth. The NEC attempts to address this problem.
Is the electrical contractor actually going to be responsible for coatings that may need to be applied to steel reinforcing bar?
Section 250.68(C)(3) of the 2017 NEC states, "The rebar extension shall not be exposed to contact with the earth without corrosion protection." This sounds fine in theory, but in practice, this statement leaves many unanswered questions. What exactly is the "corrosion protection" supposed to consist of? Various paints and epoxies are available for steel reinforcing bar corrosion protection. Is the electrical inspector actually going to be responsible to inspect paints and epoxies? Some coatings have a warranty of only a few years. How will an electrical inspector be able to determine the correct coating was applied—and at the proper thickness, no less?
Along with the rustproofing issue comes the additional problem that the below-grade portion of the rebar will more than likely be covered with dirt when the electrical inspector comes to perform the inspection (if it is extended outside the building). Should electrical inspectors require the electrical contractor to "dig up" the rebar extension at the time of inspection if the corrosion protection isn't immediately visible? Or should inspectors simply red-tag the job for "covered before inspection" and leave? To reiterate, this requirement to use corrosion protection sounds grand in theory, but in practice, it creates a snowdrift of enforcement issues.
Should one of the most important parts of the electrical installation even be allowed to utilize forms of corrosion protection?
We aren't simply talking about a piece of underground metal conduit, perhaps for a feeder. The grounding electrode system is one of the most important parts of the electrical system. The corrosion and enforcement problems can be totally eliminated by requiring the rebar extension to be turned up above slab with a 90-degree bend into a wall cavity where the wire-type grounding electrode conductor can then be connected to the extension and run to the main service disconnect. This is all extremely simple to accomplish. The more experienced electrical contractors that I see do this usually turn the rebar up into an interior garage wall. Then a blank electrical plate is used after the sheetrock is installed to make the connection accessible after installation.
The rebar extension is accurately described as a conductor, which gives rise to yet another issue. What jumps out at me here is that, if the rebar extension is in fact "a conductor" used for grounding, then it should have a specified method of connection. Take a quick gander at Section 250.8. I fully understand that steel reinforcing bar is not a "wire-type" conductor, which would have to be connected using one of the methods described in Section 250.8. But I think 250.8 is self-evident and makes my point: since this widget is used for system grounding, exactly how the connection is to be made should be very specific.
Currently, the NEC ignores the overlap issue. It should be noted, however, that reinforcing bars are required to have proper overlap per the building code. For example, if there is No. 5 rebar in the footing that is being spliced onto another, there will need to be approximately 25-inches of overlap for a tension splice. Proper lap is usually defined as being 40x the diameter of the reinforcing bar. Hence, in the case of a No. 5 rebar, this distance works out to be 25 inches. The length the lap varies depends upon the concrete strength as well as the rebar grade, size and spacing.
Certain jurisdictions allow the 90-degree rebar extension to be installed perpendicular to the footing steel. This creates a mere 0.63 inches of overlap at any point that the extension is tied to the footing steel—usually by means of a common steel wire tie. Is 0.63 inches of steel-to-steel overlap enough? Will this minimal lap continually maintain an inherently low enough resistance-to-ground to prevent damage to the footing during lightning events and withstand the test of time? There is no test data on this.
Some jurisdictions require the "full lap" as the building codes mandate. Others are making up their own rules. Oregon comes to mind—the state of Oregon has incorporated into their building code that, if a rebar extension is utilized for grounding electrode purposes, it must have at least 12 inches of lap (2017 Oregon Residential Specialty Code, Section R403.1.8). I feel that the NEC should describe the required manner in which this grounding connection needs to be made; simply leaving it up to the installer creates inconsistencies from jurisdiction to jurisdiction—and we are supposed to have a National Electrical Code. Perhaps it doesn't need to be a full tension splice per the building code, but the contact length should be of some determinate value. Perhaps the answer is to go with the Oregon model.
The solutions that I've described herein are very easy to accomplish. Building officials have much to consider when they decide what will be allowed (or not) when the rebar sticking-out method is tried. In my opinion, the best concrete-encased electrode is made by strict compliance with Section 250.52(A)(3), using either of the following:
- Route the grounding electrode conductor into the footing and connect to one or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of not less than ½ inch in diameter, installed in one continuous 20-foot length, or if in multiple pieces connected together by the usual steel tie wires, exothermic welding, welding, or other effective means to create a 20-foot or greater length
- Place 20 feet of bare copper wire, not smaller than 4 AWG, in the footing. The 20 feet of copper wire can simply be twist-tied to a piece of footing steel in a few locations. I would use some electrical tape around the footing steel at the points where the copper wire is twist-tied to prevent any possible galvanic corrosion to the steel. Then route this wire to the main service disconnect location.
The concrete encased electrode must be encased by at least 2 inches of concrete and located within a portion of a concrete foundation or footing that is in direct contact with the earth. The above requirements are quite simple to accomplish. This is the method that originated from testing performed by Herbert G. Ufer back in the 1940s. Sticking with the tried-and-true (UFER) method per 250.52(A)(3) will ensure a reliable grounding electrode system that has more than adequate testing and substantiation to back it up.
And...it doesn't leave a sharp edge!