Sean Breheny wrote: > On Fri, Dec 11, 2009 at 3:33 PM, Dave Tweed wrote: > > YES NOPE9 wrote: > > > However you choose to use the oven, you may want to ground the metal > > > frame work to earth ground as well as to electrical ground. > > > > No! That would be a code violation! At least, in the US. > > > > Electrical ground is supposed to be bonded to earth ground at exactly > > one point, usually at the service entrance or the first distribution > > panel. > > Can you point me to a reference for that? I just looked at my copy of > the US National Electrical Code (2005 version) and I can't find any > prohibition on multiple connections between the building grounding > system and earth ground. Perhaps you are thinking of connections > between neutral and ground, in which case I definitely agree that > there should be only one of those connections. I think that the poster > was suggesting merely that the oven case be connected to BOTH the > green wire from the outlet AND an earth ground rod directly. I don't > think this really does anything useful in this case (i.e., it is not > really an adequate protection against shock), I don't think it would > be harmful, either. If what you were saying were true, then RF > transmitting equipment which had a separate RF earth ground would have > to be chassis isolated from the building AC ground, which it usually > isn't in my experience. No, I don't have a reference close to hand, and you may be right. Perhaps I'm thinking that what isn't allowed is multiple earth grounds that are not electrically bonded to each other. I think the concern is that if the electrical grounding system is required to carry full load current because of a fault in an appliance, then if there are multiple disjoint ground segments, the impedance between them (through the earth) would be too high and there would be a safety hazard. Sorry, it was a knee-jerk reaction, and I really couldn't see a good reason for a separate earth ground on an oven anyway. -- Dave Tweed -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist