Jim, While the Neutral (the white wire in the US three wire power cable) must be bonded to ground at the service entrance and nowhere else, by code the Neutral must ** NOT ** be bonded to the case/chassis of any equipment (e.g., white should never be connected to the case) so the neutral is not at issue here. However, the SAFETY ground (green wire/round pin) is also bonded to ground at the service entrance - and in most residential installations ONLY at that point.
It is this situation, where the safety ground (chassis) and the shield of the coaxial cables (also connected to chassis) are at different potentials that is potentially unsafe. First, the "safety ground" conductor in most residential wiring is no larger than #10. In a lightning strike, currents WILL flow on the safety ground. Those currents can make the chassis/cabinet of anything connected to the power lines HOT and can be dangerous. The ONLY way to prevent this issue is BOND the coaxial entry window, cable TV entry, satellite TV entry, telephone entry, and power entry ... in addition, any other conductor (water lines, gas lines, power to outbuildings or landscape lighting, etc.) that enter the home should be bonded to the common point. Where those items do not enter the building at the same place it may be necessary to install a ground ring (heavy wire with multiple ground rods) around the entire structure and tie each conductor to that ground ring. Again, the key is to insure that the individual "grounds" rise and fall together and can not become separated and therefore pose a danger to either persons or equipment. 73, ... Joe, W4TV > -----Original Message----- > From: elecraft-boun...@mailman.qth.net > [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Jim Brown > Sent: Thursday, January 21, 2010 12:42 PM > To: Elecraft List > Subject: [Elecraft] Was Grounding negative side of power > supply? -CORRECTING A SERIOUS ERROR > > > NO, NO, NO! > > Joe, who rarely ever gets it wrong, has led us down a VERY > wrong path, > and you, who also rarely get it wrong, have followed him. :) > > It is the NEUTRAL that must be bonded to EARTH and SYSTEM > GROUND at the > main panel/service entrance, and ONLY at that panel. An additional > NEUTRAL connection to ground (or the green wire) is what > causes an unsafe > condition. > > Multiple paths to earth for the chassis of equipment are a > GOOD thing, as > long as they are all bonded together. in fact, safety codes and good > engineering practice all say that you can have as many connections to > EARTH as you want, that more connections are better, AND that all of > these earth connections MUST be bonded together by a low > impedance path. > > On Wed, 20 Jan 2010 22:46:54 -0500, Don Wilhelm wrote: > > >Joe and all, > > >I would also like to point out that the situation Joe presents can be > >the source of "sneak ground path currents" which can > contribute to noise > >at your station. > > I suggest study of my power point on Ham Interfacing to > understand what > you are calling "sneak ground path currents" -- indeed, they > are nothing > more than leakage currents from the hot side of the AC power > line through > capactance to the chassis of equipment. This capacitance > includes bypass > capacitors (including those in line filters) and the stray > capacitance > between the power transformer primary and its frame, which is > bonded to > the chassis. > > http://audiosystemsgroup.com/HamInterfacing.pdf > > For more on power and grounding, see > > http://audiosystemsgroup.com/SurgeXPowerGround.pdf > > >By all means, connect any ham related ground rods to > >the AC mains entry point ground rod. I don't care how you > accomplish > >that - just "do it". If it reduces noise in your receiver, > that is a > >benefit, but if not, be assured that your shack will be a more safe > >place to inhabit. > > YES! > > >73, > >Don W3FPR > > >Joe Subich, W4TV wrote: > >> This creates a situation that is potentially hazardous > >> to your equipment. The AC "third (green) wire" is supposed > >> to be connected to ground only at the main panel/service > >> entrance. > > WRONG. See above. > > 73, > > Jim Brown K9YC > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
