Eric & Jeff, Would it be reasonable to consider that since one outlet is coming from the generator system and the other from the mains that the entrance and sources are far apart. If far apart on gound/safety or neutral could be at a different potential. I am sure they make there way back to the same point, but could be in 1000s of feet of wire.
If this were the case I would not want to connect together for a number of reasons. They could set up a loop from various sources of induced voltages. If GFI were involved then this could set up for false tripping of the breaker. 73, ron, n9ee/r >From: Eric Lemmon <[EMAIL PROTECTED]> >Date: 2008/07/18 Fri PM 09:35:04 EDT >To: [email protected] >Subject: RE: [Repeater-Builder] Switching a Repeater Betwen AC Sources > >Jeff, > >Whether multiple ground paths exist is irrelevant. What the NEC requires is >a direct, low-impedance fault return path for each branch circuit, >considered individually. You cannot dispense with any ground paths because >you think there exists alternate paths. While it is true that parallel >paths may decrease the total impedance to a fault on any one branch circuit, >that in no way constitutes license to eliminate a required grounding >connection. > >73, Eric Lemmon WB6FLY > > >-----Original Message----- >From: [email protected] >[mailto:[EMAIL PROTECTED] On Behalf Of Jeff DePolo >Sent: Friday, July 18, 2008 7:50 AM >To: [email protected] >Subject: RE: [Repeater-Builder] Switching a Repeater Betwen AC Sources > >> The primary purpose of the equipment grounding conductor >> (green wire) is to >> provide a low-impedance path for fault current on a branch >> circuit. The >> lowest-possible impedance is realized only when the EGC is >> routed alongside >> the phase conductor. Article 250.24(C)(1) states: "This >> conductor shall be >> routed with the phase conductor..." I didn't quote the entire >> sentence, >> because it is very long. > >I understand that. What I was saying is that isn't the *only* ground path. >You're almost guaranteed to have multiple ground fault paths, therefore >EGC's from both systems are already tied together by virtue of those other >paths. Even if you didn't intentionally jumper the EGC's together, if you >had one device plugged into one outlet and another plugged into another >outlet and both devices mounted in the same rack (or, even just sitting on >top of each other), the EGC's will be electrically joined through the units' >metal cabinet exteriors. > >> The reason for keeping the equipment grounding conductors >> separate is very >> simple; we are talking about a hospital, not some ordinary >> radio shack. >> The critical (red) buss likely feeds catheter labs, dialysis machines, >> mechanical respirators, and similar equipment that is >> connected to human >> bodies. Even a few milliamperes of stray current flowing through a >> grounding conductor may take a side trip through a patient's >> heart and kill >> them. > >Well, now we're getting into a completely different topic. Line powered >medical equipment is wholly isolated from the patient. While I'm no expert >on the subject, there's something called the isolation barrier which wholly >isolates the patient from the electrical system. > >> One of the previous posters suggested putting the computer on >> the white >> buss, with the repeater on the red buss. That's a good idea, >> but be careful >> to use a fiber-optic link to pass data between them, else the >> two devices >> will have a common ground connection through the data cable's shield. > >Depending on what the interface is between the two, that may or may not be >necessary. Twisted pair Ethernet is transformer-coupled, so no additional >isolation is necessary (just don't use shielded cable). For simple things >like control logic (PTT, COR, whatever), just use an optocoupler. For >audio, transformers. > >--- Jeff WN3A > > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
