wire size for grounding panels

This is from the 2002 NEC. The NEC is revised every three years.
http://photovoltaics.sandia.gov/docs/PDF/PV_grounding_CC_HP_102.pdf

here is the link to the newest version of pv and nec code, suggested practices. 

#6 bare copper with lay in lugs or split bolt lugs is commonly used in pv source circuits to a combiner or pass thru box, and after a combiner or pass thru the same size conductor as the largest current carrying conductor is typically used.

http://howto.altestore.com/Reference-Materials/National-Electric-Code-and-Solar-Electric-Systems/a45/

james,
altE staff

James - you cannot run the equipment ground as you propose....According to NEC Article 690.43, the equipment ground must be run the same raceway as the circuit conductors.  Basically the whole system is grounded together.

-BF

hi bruce,

nice post.  the one thing i would like to add is that in some cases it is possible to have egc and grounding electrode separate from that of the remainder of a system, although not for james j with his modules on a building (that contains the bos).

here is a link to an old john wiles article that describes the "seperately derived system" in which i believe in cases of physical distance between array and the building which it serves, the equipment grounding may occur at the array, go to its own grounding electrode while not carrying egc in the conduit to the building.  upon reaching the building the BOS equipment is all bonded as appropriate and tied in with the building's grounding system and electrode(s).

http://www.nmsu.edu/~tdi/pdf-resources/cc74.pdf

looks like this is still valid in 690.47D 2008 version, but eager to hear others' thoughts on this.

cheers,

james
altE staff

right on. 

in james j case they are roof mounted, so in theory at site of first enclosure (combiner or pass thru)on roof,  the egc, along with pv source circuit wires, transition from bare copper and use-2/rhw-2 respectively, to more "normal" conductors like thhn or so run together in conduit as pv output circuit, as Bruce F suggests.

james
altE staff