On Sunday 27 December 2015 17:07:15 John Thornton wrote: > I've built a bunch of automation machines for Briggs and Stratton and > they never pull a neutral only 3 240v hots and a ground. We always > have a control transformer for the 120v stuff... I have the same here > now.
After an hours searching thru it, and its the 1996 issue, a 240 volt single phase line w/o a neutral is legal if it goes only to that machine AND the machine was designed for that power configuration, eg is designed to run on 240 for everything. IOW if it goes anyplace else in the building besides that machine, it has to have a neutral too. And of coarse grounded is a given. So in your case, you can utilize a 240-120 stepdown that is NOT an autoformer. And from whats been said, that is what you are doing. However, speaking as a C.E.T., not having the neutral so that the filters you are installing can ship their noise back up that separate circuit, effectively isolated from what is supposed to be a nice quiet ground, does seem like it would put a lot of the absorbed noises into the grounding system. And unless putting the filters in fixes it, making me just a worry wart, I believe this may be much of your noise problem. Since we've come 19 years into the future since my copy of the NEC was put to bed & sold, with more efficient (and more noise sensitive) ways to do things now, I'd expect that a current copy of the NEC would more than likely have some additions designed to head off problems like this. Unfortunately a current copy is now at or somewhat north of a 120 dollar bill. > On 12/27/2015 3:52 PM, Gene Heskett wrote: > > On Sunday 27 December 2015 16:17:20 John Thornton wrote: > >> well there is no neutral because it's a 240vac circuit only... > > > > The only reason there is not a neutral is that the wire was never > > pulled. And I am not sure that missing neutral is NEC kosher. My > > copy is now 17 years old, so I think I'd check a newer one to be > > sure. With it, you wouldn't need the stepdown and isolation tranny > > because you would then have a pair of 120 circuits available in the > > machine. But those loads MUST return on the neutral, they cannot > > use the static ground. > > > >> On 12/27/2015 12:16 PM, Bruce Layne wrote: > >>> On 12/26/2015 06:51 PM, John Thornton wrote: > >>>> There is no neutral in the machine, only L1 L2 and GND. The > >>>> Neutral for the house is bonded to ground at the panels. > >>> > >>> Electrician's Joke: > >>> > >>> Q: What's the difference between neutral and ground? > >>> A: About six inches. > >>> > >>> There's a very good reason the return current is carried on the > >>> neutral and the ground should not carry any current in normal > >>> circumstances, but we do need to understand that electrons don't > >>> care about our conventions. They're just as happy returning via > >>> the ground wire. They don't know that the green wire is off > >>> limits for all but emergency traffic. > >>> > >>> The concept of ground/neutral functional equivalence is also a > >>> real life saver for anyone who might otherwise consider standing > >>> barefoot on a basement floor while hot wiring any line powered AC > >>> circuit. > > > > Cheers, Gene Heskett > > ---------------------------------------------------------------------- >-------- _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
