On Sat, 27 Mar 2010 09:32:12 -0400, Don Wilhelm wrote: >An isolation transformer *does* isolate the neutral (and the hot),
NO! This is a summary of NEC (National Electric Code) requirements: The NEUTRAL of a transformer on the secondary side MUST be bonded to the equipment ground (steel conduit, the green wire, building structure, etc), and that green wire must be carried from the breaker panel to each outlet and to the transformer. The neutral conductor that feeds the primary side of the transformer must be bonded to ground at the service for the building (that is, the main breaker panel). And, as we all know, all groundes must be bonded together. Thus, an isolation transformer does NOT isolate either the neutral or the equipment ground. What an isolation transformer DOES do is reduce the voltage between neutral and ground to zero. It also shortens the return path for leakage currents on the green wire -- they now return to that transformer, not to the more distant breaker panel at the service entrance. This has the potential to reduce noise current on the shield of signal cables. BUT -- the simple bonding regimen outlined in my Ham Interfacing Power Point is a MUCH less expensive AND more effective solution. 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
