250.52 (A(3) Concrete-Encased Electrode

Categories: Electrical Safety

This weeks column is not about a Code change it is about a common problem we all face on a regular basis.  Footer steel, when is it required to be made part of the Grounding Electrode System?  We will have to check with the building plans examiner or the building inspector and see if there is going to be steel in the footer and if it will need to be made into a Grounding Electrode?

What will require it to be made into a concrete-encased electrode.  There are three requirements to make a good concrete–encased electrode.  The first is that the rod be at least 20’ in length, and it does not have to be one 20’ piece, it can be several shorter pieces connected together to make a 20’ piece.  The second is that it has to be at least a 1/2” in diameter. and the third and probably the most important is that it cannot be isolated from the Earth by a vapor barrier.

We are creating another electrode for our Grounding System.  In section 250.50 they talk about the Electrode being present.  What do we do when it is already poured. I get calls all the time about what to do when they miss the steel in the footer.  At that point I feel that the steel is not available and although you may want to chip into a footer to find a piece of steel rebar how do you know if it is 20’ long, and is not above a vapor barrier?  I have spent time trying to come up with a solution, because chipping into a slab is probably not the best answer. You could cause cracks in the concrete by hitting and vibrating the steel rebar when chipping into the footer.  So when someone calls me in the future and they ask what to do, my solution will be to get them to dig a trench and lay a 20’ piece of 1/2” rebar and make a connection to it and then encase it in at least 2” on concrete.  Maybe next time they will remember to connect the steel and call for an inspection. 

We just need to train the General Contractors and the Electrical Contractors that if this steel if available it is required to be part of our Grounding Electrode System.  If the building plans don’t call for steel in the footer we cannot make them put it in.  It is only required when there is steel and the footer has no vapor barrier and is called out for on the  plans.



Till next time be safe and work safe



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