I question the validity of your statement that separating the grounding conductor "would greatly increase the impedance of the grounding system"
It might do this depending on the route the ground wire takes, but if the installation had a 4 inch ground foil running around the perimeter of the building and every grounding conductor ran from an outlet to this ground foil, wouldn't that REDUCE the impedance and possibly offer better ground conduction? Seems to me that a long #12 ground wire, from the outlet all the way back to the service panel, would have a higher impedance. I agree with the rest of the paragraph below however. How often is R56 updated? Does R56 mention somewhere that local regs take precedence, or that NFPA codes supercede R56? Is R56 just a thorough collection of installation guidelines and recommended practices? I've never seen a copy so I'm asking merely for my own education. Bob M. ====== --- On Wed, 4/8/09, Eric Lemmon <[email protected]> wrote: > From: Eric Lemmon <[email protected]> > Subject: RE: [Repeater-Builder] Re: Motorola R56 grounding > To: [email protected] > Date: Wednesday, April 8, 2009, 10:04 PM > Martin, > > Sure! The National Electrical Code (NEC) requires > that the equipment > grounding conductor (green or bare wire) must always follow > the same route > and wireway used by the supply and return conductors. > There must never be > any deviation from this basic requirement. The three > wires (hot, neutral, > and ground) feeding every receptacle must always run > together, but the R56 > manual proposes that the grounding conductors of some > "technical" > receptacles shall follow a path separate from the hot and > neutral > conductors. That is not allowed by the NEC, since > that would greatly > increase the impedance of the grounding system and thereby > reduce the > protection of the circuit against faults. Also, the > NEC requires that the > system grounding conductors, equipment grounding > conductors, and lightning > protection grounding conductors must ultimately be bonded > together to create > ONE grounding system. The R56 manual proposes a > scheme that creates > separate grounding circuits that can create dangerous > voltages on some > circuits if a fault occurs on another circuit. > Despite some really creative > schemes to create separate grounding paths, such schemes > are not allowed by > the NEC or by state electrical codes based upon the NEC. > > Readers following this thread should be aware that the NEC > is updated every > three years, and becomes law as each state or commonwealth > ratifies it > through legislative action. The current edition of > the National Electrical > Code, NFPA 70, is the 2008 edition. > > 73, Eric Lemmon WB6FLY
