I have an overhead light fixture that was failing intermittantly.
I opened the J box of the on/off wall switch controlling that overhead
I have a twisted bundle of 4 white wires stuffed into a wire nut.
The white neutral for the overhead light had loosened from the group.
When I tried to reattach it properly to the other three twisted
together, tiny sparks flew.
One of the neutral wires is hot.
I isolated and disconnected this neutral, and reconnected the 3 other
Everything upline from there now works.
I get a reading of 120v when I attach a voltmeter to the hot white
wire and ground it to the box.
When I short the wire against the metal box, BIG sparks fly.
I don't want to connect it to the other white wires again
The disconnected wire is to the floor outlets in one room.
Prior to my disconnecting this wire the floor outlets worked.
(Last time someone worked on electric in this room was over 7 years
What would cause this wire to be hot, yet still appear to function?
If I had an incorrectly polarized outlet, wouldn't it short out
against the ground?
Am I missing something Any ideas?
One of the uses on that circuit has the wires on the wrong screws.
Color on brass, white on silver.
If they are all receptacles, get one of these to check polarity
Keep the whole world singing . . . .
Is there any voltage between the white neutral wires and the green (or bare)
ground wiring? There should be none. If there is, investigate that first.
Your neutral is not attached to the safety ground.
Verify that the outlets don't work now that they are disconnected. If they
still work, you have another problem.
Perhaps some one confused black and white. Have you disconnected the black
wire going to those floor outlets?
Draw the existing wiring diagram. A picture may help you sort it out.
The white wire is a return path for hot to earth ground. If something on
one of those outlets downstairs is actively used, all what you see it
normal. Unplug all appliances et all downstairs outlets, try it again.
Thanks for the replies.
Dave seems to have hit on the proper solution for my particular
I thought I had unpugged or shut off everything prior to my original
tests. I Missed a computer monitor and a clock.
With thhem removed - No more voltage. no more sparks.
I'll rewire it all in daylight tomorrow.
Glad you found the "culprits". Some stuff may have a standby condition,
still drawing power. Best to physically disconnect all. Just hook the
neutral back to the way it was.
Retired USN Chief Fire Controlman
Because it is the return path for the circuit, the neutral is,
in essence, the hot. So just like finding current between
your black wire and the ground, you find current between the
neutral and the ground.
Unplug the device that is providing the circuit continuity and
the phenomenae goes away.
[Sorry if this is a duplicate.]
Sure, there will be current on the neutral, equal to the current on
the hot for a 120V circuit. But the load will cause a voltage drop of
almost 120V, so while the hot will be 120V from ground, the neutral
should only be millivolts above ground. I think that if the OP truly
measured 120V between a neutral and a ground, just having a device
plugged in downstream doesn't explain that.
Maybe what was happening was that with the downstream neutral
disconnected (no circuit), the voltmeter was giving a phantom 120V
reading due to the induced current from the parallel hot conductor.
As a separate matter, touching the downstream neutral to the grounded
box, while a downstream load was plugged in, completed the circuit for
that load, causing the spark.
Any residential circuit on which has power drawn from the hot needs a
neutral. The neutral carries the current to earth ground. The
difference/potential in those conditions is the neutral will be at a
potential equivalent to the difference voltage drop of the the load and the
actual supply voltage AND earth ground. Thus, the neutral is hot minus the
load vs. earth ground is the actual potential.
The voltage drop is negligible. The current draw may be more perceptible,
but not measured in this case.
A voltage drop to zero across a load is effectively infinity impedance. No
current can occur in such condiitions. No current means no electrical flow.
Wouldn't warm your tongue, never mind a spectacular electrical air arc.
What's present on one part of the circuit on the same wiring is also present
down the line.
Actually, it returns it to the source, the power company
transformer--the earth ground is relevant only because the local
transformer is center tapped and earthed.
Not sure what you are saying here. If the circuit consists of Hot
Transformer terminal -> Hot wires -> Load -> Neutral wires -> Grounded
Transformer terminal, then the voltages above ground at each point
might be 120V (Transformer), 119V (Hot wire at the Load), 1V (Neutral
wire at the Load), 0V (Grounded Transformer terminal). Under normal
operation, there will never be a 120V voltage difference between a
neutral and an earth (ground).
As for the spark, it indicates current flow and was probably just due
to completing the circuit by connecting the neutral to the EGC, which
is bonded to the grounded service conductor at the main disconnect.
Think of it this way. The receptacle is acting as an open point between the
black and the neutral. If the neutral is open at another point and a lamp is
plugged into the receptacle, the lamp closes the open point in between the
black and the neutral at the receptacle, and the neutral has just become an
extension of the black up to the open point. That's why he measures 120V. If
the open point was connected like it should have been, the current would
return to the ground at the panel and he'd measure zero volts between
neutral and ground.
Ah, of course, thanks for the explanation! Sorry to have been a bit
slow on the uptake here. When there is no circuit, there is no
current, so there is no voltage drop across the load, so the measured
voltage on the open neutral is 120V.
Begging your pardon here. Two phases of voltage normally enter a home at
the entrance panel. One phase is strictly used for 115/120 VAC to outlets,
lighting and such.
Earth ground is introduced at the end of the utility providers entry to the
users panel. It can be one panel located near the utility pole or outside
the house or a panel inside of the house. Depending where this specific
panel is, determines the function of earth ground at that point. There is
no physical tie to any of the utility regarding earth ground and the users
The users panel where the 115/120 VAC is introduced is where neutral is tied
to earth ground. Neutral goes nowhere else on the return path.
Voltage potential measuring is assuming there is an open between the 2
points measured. IE - hot and neutral. When measuring between the hot and
neutral across a load, that measures the difference accounting for the load.
If that load exists, and a spark gap is made between the neutral and earth
ground, the remaining voltage potential jumps the gap to earth ground.
Creating a spark.
A simple DC battery and light bulb (load) is a good graphical representation
of the same thing. The negative side is hot. The positive side is earth
ground. The wire from the light bulb to the positive side is neutral. The
only difference is that current does not fluctuate and change directions in
a DC circuit, and voltage potential doesn't change @ 120Hz..
Dave, I think we are in agreement. I was missing the fact that with
an interrupted neutral, there is no current flowing in the circuit, so
there is no voltage drop across the load, so the load end of the
interrupted neutral is at the same voltage as the hot.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.