Are a bunch of your wires running for long lengths in parallel through
the same holes in the studs? It is a long shot, but it might be
inductive coupling. Were the circuits that had the breakers still on
loaded? That is, were lights or other things on such that the circuits
had current flowing in them?
Typically, if Romex-style cable is used the return current in the white
wire should cancel the field from the black wire and thus there
shouldn't be any significant net field to affect adjacent wires,
however, sometimes strange things can happen.
voltage is being induced in the disconnected circuit due
to its close proximity with live current carrying wires.. the
electro magnetic effect created by an conductor.
I am currently revamping a 20 year old control system, no
big deal, a few pumps, a boiler and a cooling tower... very
nice control job these guys put in... 24vdc, the wires are
all bundled nicely.. and the job as worked more or less fine
for 20 years with a few bugs no one has figured out.
in checking out I noticed all kinds of 2 to 9 volt reads in
open circuits. Fortunately there were no electronics or
logic controllers in this old system so the stray voltages
were not sending bogus signals to the electronics... but at
9vdc, and sometimes AC.. and relays operating at 24vdc... I
think they got a little sticky at times and is the source of
the unfathomable bugs.
However moi here is adding a PLC to the mix (dinky solid state
computer that does simple logic functions, 256 various
combinations)... and If I am not careful the wiring I install
will be next to higher voltage conductors that will induce
current in my PLC feed wiring.... and the PLC will go nutz...
and produce all sorts of bogus output.
a bad thang.
Fortunately I am putting this low voltage wiring in a separate
cabinet and not bundling the wire as the other stuff is
bundled so I wont get stray signals.
I almost decided to run some 110 vac transformer power wire in
the same conduit as the 24 vac control and alarm wiring some
of which would go directly to dialers.. no relay in between.
that could have been a mess because both the dialers and the
PLC are AC voltage.. *any& AC voltage... so say 15vac or 120
vac signal is acceptable as an input to the plc. That would
have been messy. The instructions with these particular
devices even say you can use DC inputs over a wide range to
trigger the PLC switching actions even though they are rated
for AC only and sell a strictly DC unit if you want one.
So what does that tell a person? That all those trace stray
voltages will create havoc in yer electronic gismo's.
Getting back to your case. Dont worry about it...while there
is voltage in the disconnected circuit, its induced and not
capable of pushing much amperage, so its harmless in a home
wiring sort of scenario/... just a faint distortion to a
circuit under load.
Following advise I plug-in the load (TV) into one of receptacles. Residual
voltage dropped to zero immediately in switched off circuit even when
measured by digital multimeter. To verify this I unplugged the TV and
voltage jumped to previous ~8-9V. Now I am convinced it is inductive voltage
induced by other hot circuit wires running close to the disconnected one. I
am calling the electrical inspector to re-inspection.
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