On 12/28/2015 04:25 AM, Dave Cole wrote: [snip] > I do a lot of machine wiring and I was redoing a machine for a major > electrical manufacturer in the US (although this particular plant does > hydraulics) > and the plant maintenance nitwits tied a relay coil between a 480 volt > hot leg and the protective ground because they did not have a neutral in > the control cabinet and they had a 277 volt relay! 8-O > > I ripped out the added "circuitry" and wrote a note to the maintenance > mgr and explained that if the protective ground wire had became > disconnected from the power feed that the machine frame would become hot > to ground through the 277 volt relay coil!
Oh boy! Some never learn how this stuff works and how dangerous it can be. For that matter; I learned, many many years ago, that the protective ground (or "earth" as it is called here) is the first pin/wire that must be connected and the last that is disconnected. Specifically with disconnection it is regardless whether it is a connector or cable you are pulling, the protection must always be the last to go. -- Greetings Bertho (disclaimers are disclaimed) ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
