This is the Sixth in the top ten Code changes for 2011, this change is really just a clarification of what we where doing out in the field. Some of the recent revisions to this had made it a bit unclear but the new language should make it easier to understand.
I get a few calls a week asking if another ground rod is required when doing a service change or a new service? “Do I need to drive another ground rod” , I tell them it depends. It all depends on what else is available at the site. Are you connected to the cold water system pipe, or the concrete encased electrode, or have you tested the single rod to see if you have 25 Ohms or less? If they answer yes then I tell them they are done, unless there are other required electrodes available. 250.50 states that the electrodes described in 250.52(A)(1) through (A)(7) if present at each building or structure SHALL be bonded together to form a grounding electrode system. Section 250.53 of the Code is fairly easy to understand. It states that you SHALL supplement a single rod, pipe or plate electrode with an addition electrode of a type listed in 250.52(A)(1) through (A)(8). The following is a list of those eight items that can or shall be used for an additional electrode(s).
(1) Metal Underground Water Pipe.
(2) Metal Frame of the Building or Structure.
(3) Concrete-Encased Electrode.
(4) Ground Ring.
(5) Rod and Pipe Electrodes.
(6) Other Listed Electrodes
(7) Plate Electrodes
(8) Other Local Metal Underground Systems or Structures.
Until next week be safe work safe
Jake