On 8/26/2015 3:07 PM, Noel Chiappa wrote: > > From: Paul Koning > > > What happened is that the "grounds" were offset enough, and with enough > > of a current supply, that the ground strap that's supposed to connect > > the row of RP06 drives melted. > > This sort of thing is a major electric code violation: you can > certainly have > > multiple services, but all the grounds are required to be connected by > > substantial wire; you're not allowed to stick ground rods in at > > multiple places and leave it at that. > > I'm pretty blown away that the various grounds could be offset by that much, > to produce that kind of current when they were tied together. Wow. > > Noel >
Consider, say, 10 circuits, 20A each sharing a neutrals. Suppose each neutral as a total resistance of 0.1 ohm. If the neutrals were done properly, the voltage drop would be 20 x 0.01, or 2 V. Share one neutral, though, and you are up to a whopping 20V. And if that happens, guess what: some of the current is going to happily use the earth ground (or an FE) as the path of least resistance.
