Re: Low Voltage on Neutral Conductor

kmans999@xxxxxxx wrote:
Tony Hwang wrote:

pipedown wrote:


<kmans999@xxxxxxx> wrote in message
news:1155225290.654800.35410@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx


Bud-- wrote:


Tony Hwang wrote:



kmans999@xxxxxxx wrote:



I would appreciate assistance in troubleshooting an electrical
problem:
I have a single-pole switch serving 3 overhead lights in basement.
All lights are inoperable. I replaced the wall switch (evem though
old
one passed a passive test) and same problem. I have 2 wires wires
entering the switch - a 3 conductor and a 2 conductor. The 2
Conductor
appears to be the feed/source. When I separate all wires, I measure
50v across the neutral (white) to the live (black) and measure 110v
between black to ground. It would appear to be a bad neutral feeding
the switch. What is the best way of troubleshooting this circuit
(other lights/outlets on the circuit breaker appear to operate
normally
so I can eliminate the circuit breaker as cause).


Hi,
Sounds like neutral wire lost continuity partial of full.

I agree.

The 50 volts you are measuring is probably from capacitive coupling
between wires - phantom voltage. If you connected a light from incoming
hot to neutral there would probably be zero volts.

The problem is probably in a neutral connection in another box. Could be
a loose wire in a wire nut or bad contact in a backstab connection
through a receptacle. (I think everyone in this newsgroup advises
eliminating backstabed connections.) The bad connection is likely in a
box with receptacle/light/switch on the same circuit that is closer to
the panel. (Could also be in another dead box, but you said there
weren't any.)

Good troubleshooting so far.

bud--


I do have many backstab connectors, mainly on the outlets rather than
the switches. I did visually check the nearest ones to the suspect
switch locality for physical problems (loose/burned, etc) but have not
yet replaced them with screw terminal outlets. Is there a proper way
to "test" these outlets rather than a visual test?



Turn off the breaker first then use an ohmmeter to check the continuity
between the wire at the back of the receptacle and the hole for the plug in
front.

Its a wasted exercise though since the act of removing the receptacle from
the j box and pulling on the wires would have fixed an open. if it were
really bad, it should just fall out. Just buy a 10 pack of recepicals at HD
and have at it.

In any case, a map of the path each branch circuit takes on its way from the
breaker box to the receptacles is very useful. Might take the opportunity
to map this branch out and tape it to the inside of the panel.

Fortunately there should be no connections buried in a wall and wires almost
never go open in the middle.



Hi,
This kind of trouble shooting I always use low input impedance analog
meter. Such as old work horse Simpson 260. On digital works I use Fluke
and o'scope.
Tony


Over the weekend I was able to identify (not 'trace' - as I have no
idea how to trace all circuits w/o schematic) all circuits working off
of the circuit breaker with the faulty circuit. I checked every switch
and every outlet and verified all "good connections". By that I mean
all had tight connections, nothing burned nor any signs of oxidation.
I did find a light switch that was in the proximity of the "faulty
switch" that appeared to be the feed. When I shorted the neutral and
hot wires at the 'faulty switch' location I was able to see the short
while reading across the N/H wires at the other switch location.
However this second switch serves a ceiling light fixture in the dining
room that works just fine. Every light fixture and outlet served by
this circuit breaker appears to work fine except for the light switch
and the 3 overhead lights in the basement that work off this
switch...which I had replaced simply to eliminate it as the potential
cause. Not being in the trade, my primary trouble shooting tool is an
analog Ohm-meter.. . . and the assistance of those on this site.

Ken


If I read that right, the neutral was also floating at the switch for the dining room ceiling light. What is the source for the neutral at that switch. The dining room ceiling light box is a prime suspect.

(If there are 3 wires from DR ceiling light to switch, the hot and switched hot wires are required to light the ceiling light. If the neutral is open to the switch, the ceiling light will still light. The neutral is only used, along with the hot, for the circuit down stream - which is your dead switch.)

One of the more useful tools can be a light bulb in a socket with pigtail leads - probe hot and neutral wires and see if the bulb lights. It will not show the 'phantom' voltage. But it sounds like you are doing OK with your meter.

bud--
.

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