ECN Forum Forums Code Related Discussion NEC & other Code issues Grounding/bonding 2 panels, 1 meter

400 amp service requires 500 mcm =380 amps at 75%. go to 250.66 a 500 requires a 1/0 copper grounding electrode conductor.
you can run a 1/0 to the ist panel then (TAP)a #4 from (OUTSIDE) the panel to the second panel.You cannot Splice (unless Cadweld or Listed compression ) and going in one panel to the Neutral bar then to the other would be like a splice , But you can Tap.(250.64d)Page 214 of the NEC 2005 Handbook shows a nice detail of this.Since a #6 copper) per 250.66(A) is the largest size wire required to a Ground rod no matter what the size service. I feel you could run one #6 from the Ground Rod or Rods to the Water line (Detail on page 215 NEC Code Handbook) and you;d be done.All of theses are also shown well in Soares Grounding book.