[OPLINTECH] Planned power outage procedure

[Nathan Eady]

Bob Neeper <neeperro at oplin.org> writes:

> This makes a remote possibility of AC coming in on neutral or even
> the ground wire.  Sometimes neutrals can even come from a different
> transformer winding than the Hot lead.  More common in plants but
> possible in large buildings.

That sort of nonsense is VERY common in homes, especially older homes,
where among other things it is common to see the cold (white wire)
interchanged with either the hot (black wire) *or* the ground (bare
wire), albeit hopefully not both on the same circuit.  

I haven't seen circuits crossed, but I *have*, in my very limited
experience (IANA electrician) seen cable from two circuits running
through the same junction box, and in other circumstances I've seen an
outlet powered from the black lead of one cable and the white lead of
another cable in the same box, based apparently on which wirenuts
appeared to have more room in them for another wire.  If those two
abberations had occurred at the same location, you'd have circuits
crossed, so I certainly believe it can happen.  I've also seen a
220-volt electric range wired in a way that bypassed the breaker box
entirely, which could easily result in a burning building if the range
and/or its cable ever develops an electrical short.

> Everything depends on the electrician.

Indeed.

So yeah, wiring weirdness can potentially occur anywhere.

> Really safe is, pull the plug and use a voltmeter (or some dongle)
> to test the circuit before plugging it back in.  Some surge
> protectors have wiring fault indication which should suffice.

In a perfect world, critical systems should ideally be powered by an
online full-time sinewave-output UPS anyway.  But those can be pricey
(albeit not as crazy over-the-top expensive as they used to be), so in
the real world sometimes things that probably ought to have them don't.

-- 
Nathan Eady
Galion Public Library