26 Aug
2015
26 Aug
'15
2:23 p.m.
On 8/26/2015 3:07 PM, Noel Chiappa wrote:
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.
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