A Contractor has used the buildings rebar system as a grounding electrode, to connect the transformers throughout the building to ground. NEC states that an acceptable grounding electrode is one that is encased in concrete at the footing all per Article 250.52(A)(3). I believe that this only applies to the 20' of continuous rebar in the footing and this does not extend the electrode all the way up the building to say the 20th floor via the rebar system. The contractor is trying to claim that the rebar is all tied together in the entire building and that this is a steel framing member and thus per NEC Article 250.52(A)(2) it is an electrode. Because this is a concrete structure, I designed the building to include a common grounding electrode conductor of 3/0 up the entire building per Article 250.30(A)(4) with taps to each separately derived system (xfrmr). I believe this section of the code was added to address this specific issue of using the rebar as an electrode as if it were building steel framing member. Article 250.30(A)(7) offers other options for a grounding electrode, which includes all those stated in 250.52(A) if one of the two in 250.30(A)(7) are not available. In no case does the NEC allow the buildings rebar to be used as an electrode, only that portion which complies with article 250.52(A)(3). I know this is confusing but that is my problem also. Is this installation in violation of NEC? And if so which specific Article? Or am I already on the right page by saying a common grounding electrode conductor must be installed (min. 3/0) and connected back to the main service electrode system near as possible to the service or electrode system, and each separately derived system must have a tap to connect to this electrode conductor per Article 240.30(A)(4), and the rebar can not be used?