A tale of woe, including carelessness, stupidity and laziness....
cube1 at charter.net
Wed Aug 26 16:23:44 CDT 2015
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.
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.
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