This weeks news letter is about what we call a Uffer Ground (Concrete encased electrode) 250.52(A)(3). It seems to be a mis-interpreted Code section, that a lot of contractors and inspectors alike do not understand. This Uffer Ground is a type of grounding electrode and not a point to bond the steel in a building slab. We are not bonding the steel in a slab of a building, we making the steel in the slab of a building into a grounding electrode, one 20’ piece.
As stated in the Code section we are to take 20’ of rebar and run #4 cu.to it and use it as one of our required grounding electrodes, when it is available. Yes, if it is available. If we missed it on the pour of the slab it then becomes unavailable, so we use some other method. If you miss it and it is called for on the plan you will need to get the plans changed to show another method. It is not required to chip into the slab and expose a piece of steel so that we can accomplish this, because how do we know it is 20’ long.
So if your slab has several separated steel electrodes (ones that are 20’ and are available) you don’t have to bond them all together to form one, we just need one. (see the highlighted section below) Then next time you fail an inspection for not boding all the steel pads in a home, remember “YOU DON”T HAVE TO”!!!
One other note on this electrode is the informational note at the bottom of the section which states that the concrete should be in direct contact with the earth and not sitting above a piece of plastic vapor barrier.
250.52(A)(3) Concrete-Encased Electrode. A concrete-encased electrode
shall consist of at least 6.0 m (20 ft) of either (1) or (2):
(1) One or more bare or zinc galvanized or other electrically
conductive coated steel reinforcing bars or rods of not less
than 13 mm (1⁄2 in.) in diameter, installed in one continuous
6.0 m (20 ft) length, or if in multiple pieces connected
together by the usual steel tie wires, exothermic welding,
welding, or other effective means to create a 6.0 m (20 ft)
or greater length; or
(2) Bare copper conductor not smaller than 4 AWG
Metallic components shall be encased by at east 50 mm
(2 in.) of concrete and shall be located horizontally within that
portion of a concrete foundation or footing that is in direct contact
with the earth or within vertical foundations or structural
components or members that are in direct contact with the earth.
If multiple concrete-encased electrodes are present at a building
or structure, it shall be permissible to bond only one into the
grounding electrode system.
Informational Note: Concrete installed with insulation, vapor
barriers, films or similar items separating the concrete from the
earth is not considered to be in “direct contact” with the earth.
Next we have a new type of connector in a meter can given to me by Howard of Stuart.
Till next time be safe work safe.
Jake