On Saturday 26 December 2015 19:32:31 John Kasunich wrote: > On Sat, Dec 26, 2015, at 06:40 PM, Bertho Stultiens wrote: > > On 12/27/2015 12:22 AM, John Thornton wrote: > > > It's single phase 240v but no neutral, each leg is hot 120v and if > > > measured to ground you get 120v. Measured between the two hots you > > > get 240v. > > > > Ah, it is a two-phase system (because you still have a neutral). > > Each phase is 180 degrees apart from each other. > > > > The generation of the two phases comes from a transformer with a > > center-tap denoted as neutral N. Is the neutral floating or > > connected to earth locally (where it enters the house) or maybe at > > some farther away tranformer-station? > > John T has already responded with the specifics of his situation. > Some more background on US residential power: > > The transformer is typically mounted on a pole and serves several > houses. The neutral is connected to a ground rod at the base of the > pole. There are three wires from the pole to each house - L1, L2, and > Neutral (no ground). > > Each house has a ground rod. The neutral from the transformer, the > house ground rod, a connection from the house cold water plumbing (if > copper), the neutrals from all the receptacles, and the ground wires > from all the receptacles are all tied together at a large bus bar in > the main panel. > > Other than the tie point in the main panel, neutral and ground are > kept separated throughout the rest of the building, including through > any sub- panels in garages, etc. > On thing should be the rule though, John. If there is current from anything, motor, lamp, whatever, it goes back on the neutral. The ground, more properly called the static ground is only to establish a grounded condition for the frames of the equipment, independently. If something shorts to the frame, then there will be current flow, and a voltage WILL be developed on the static ground circuit. Under ideal conditions, a GFCI should shut that whole circuit off almost before you can feel a shock.
The problem with using GFCI's for us with our bigger spindle motors & 5-15 HP air compressors is that the higher current rated ones we would need are gawd-awful expensive. A 20 amp GFCI was in the $50 range the last time I pulled one off the pegbord to read the fine print, although there are certainly cheaper places to get them than Lowes/Home Depot. > > John Kasunich 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
