I was adding another circuit for a bathroom which required me to remove
the breaker box panel for the first time. I notice while looking inside
the breaker box; I spotted a red copper ground wire (like the copper
wire heated up and discolored) this is a 12/2 cable that runs outside
underground about 90ft. to a pool GFCI outlet. I was curious about
this; so I shut the 20A breaker off and disconnected the ground wire
from the neutral busbar and I saw a faint arc between the ground wire
and busbar (I did this with the power off to that circuit). So I put a
multimeter across the ground wire and busbar; it read: 47.3 volts. Any
The Neutral (white) and Hot (black) wires in this cable look fine and I
checked the wiring at the GFCI outlet box at the pool and the ground
wire is very red at that end.
I never had this breaker trip or any other weird problems; the GFCI
outlet works fine. Could lightning struck the pool at one time?
You had to have read the 47.3 volts with a digital multimeter. Disregard
almost anything a digital multimeter tells you during troubleshooting of
electrical power systems as they are too sensitive to stray voltages on
disconnected wires to be of any use. The neon test lights are almost as bad.
Use an analog meter or incandescent test light instead.
If there is any significant current leakage to the ground wire you will just
have to disconnect things until it goes away to find the source. I do not
believe you have a problem there, but I could be wrong.
The discoloration of the ground wire is very unlikely to be due to any
overheating without other supporting symptoms. I have found some cables with
discoloration on bare or insulated wires when new. Most of the wires are
nice and shiny, many are dull, and some are really grungy with plastic stuck
Your situation is definitely worth checking out, but from your description I
personally do not think anything is wrong. If you are unsure you probably
should have someone else look it over.
Sorry I can't address the original post. My server did not deliver it.
The code requires green or green with yellow stripe, or bare. Where I come
from people don't worry too much about the color. Black is common with a
little green tape at both ends for identification. The color is not your
You say you have 47.3 volts between the ground wire and the busbar (assuming
you meant the grounding bus bar or neutral bar at first means of
disconnect). That could be a problem, especially since it is going to the
You want an electrician to check it and a good one that really understands
grounding. You see when large spaces are involved between points , there
will be differences in voltage. Electricity exists everywhere. There are
chemically induced currents , rf currents, all sorts of currents going to
ground. Very often there is a potential voltage between the ground of one
space and the ground of another. Systems over great spaces have grounding
grids to keep these transient currents drained one into the other and in
A few volts of potential is very common, but you note 47.3 volts. That is
some heavy voltage around a pool. It could just be some low amp
capacitance, but that should drain away quickly upon grounding and take time
to build back up. The indication is there is a ground fault from some
source near the pool or passing through the area. You need to find what is
causing that and have it repaired.
Because your GFCI doesn't trip does not mean you don't have a problem. The
individual GFCI works like this: The current that goes out the black wire
and comes back on the white wire (changing directions 60 times per second)
is measured. So long as both measurements remain within a certain tolerance
of each other (black wire vs. white), there is no indication of a ground
fault....for that circuit. If you have current flowing on the ground
wire....that would indicate either the GFCI is not working.......or the
ground fault is from a source other than the GFCI. That other source is
using the ground path of the ground wire. Either way it could be dangerous.
This one could present a head scratcher for even the best of electricians.
Randy R. Cox
40+ volts different between a buried conductor and the building's
earth ground is too much. And the GFCI does not trip (this assumes
GFCI is in breaker box - not at outside receptacle)? That breaker box
GFCI action means 90 feet of black and white wires are not part of a
circuit that creates a rather unacceptable 40+ volts. How is earthing
for that breaker box? Is it securely connected to a nearby and
properly installed earthing electrode? Is a second ground wire connect
to where cold water pipe enters building? These missing ground wires
might mean transient currents has to find earth via buried 90 foot
conductor and have now blown a hole in cable's insulation jacket.
For some reason you have currents flowing through a safety ground
wire that in normal operation should have no currents - significant
currents indicated by sparking. That and the 40+ volts is not
acceptable expecially with electicity running to outside water. Yes,
clearly a definite problem exists. Above are some first things to
suspect / inspect. Interesting symptoms - GFCI does not trip and yet
clearly there are unacceptable currents on a now reddish safety ground
wire 90 feet to outside water.
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