Can you tell how this bathroom light-switch circuit is wired based on these
15 highly annotated photos?
The wierd thing is that the CGFI circuits (apparently downstream of the
light switch) stopped working altogether. There is no current in the GCFI
boxes and in adjacent outlets.
Another wierd thing is the voltage CHANGES when the adjacent bathroom light
switch is turned on or off (but it does not change if I remove the bulbs
from the adjacent light switch).
Can you help me figure out the proper way a light switch should be wired to
This question is a followup to a previous question on the same topic.
All the circuit breakers operate something (although some have tons of
circuits on them and others have almost none).
Wiring isn't as easy as it looks!
Can you help me figure out how to hook a simple light switch in this
Here is the wiring table (see the well annotated photographs)
The wiring table is as follows (parenthesis are when I turn on the adjacent
bathroom light switch which causes the voltage to change for some strange
reason in the first bathroom).
left-most white to ground = 0 volts (0 volts with the adjacent switch on)
right-most white to ground = 26 volts (117 volts with adjacent switch on)
black to ground is 119 volts (118 volts with the adjacent switch on)
red to ground is 119 volts (117 volts with the adjacent switch turned on)
left-most white to red is 26 volts (117 volts with the adjacent switch on)
right-most white to red is 0 volts (15 volts with the adjacent switch on)
black to red is 83 volts (0 volts with the adjacent bathroom switch on)
white to white is 26 volts (117 volts with the adjacent switch turned on)
black to left-most white is 118 volts (118 volts with adjacent switch on)
black to right-most white is 83 volts (0 volts with adjacent switch on)
Can you give me an idea of why the voltage changes when the adjacent
bathroom light switch is turned on with bulbs in the sockets of this
adjacent bathroom light switch (which is a two-wire switch in this adjacent
GFCI measure the current in the active and the current in
the neutral. If the two currents are the same the GFCI does
not trip. If the neutral is connected to another active not the
one coming from the GFCI then the current in the neutral
coming from the GFCI will be different than the active coming
from the GFCI and the GFCI will register a ground fault and
not reset. This is called crossed neutrals.
The Active and neutral going to the GFCI is the same as that in
the House circuits and can be used to supply lights or anything
else. But the Active and neutrals leaving the GFCI can only be
used with each other and cannot be connected to other actives
or neutrals otherwise the GFCI will trip and refuse to reset.
As an example a GFCI has a active and neutral connected to a
power outlet. Then somebody splices into the neutral and runs
it to a light with a different active as soon as the light is turned
on the GFCI Trips
On Tue, 27 May 2008 22:47:09 +1200, Telstra wrote:
I must have this "crossed neutrals" situation. I'm still figuring out what
you wrote (thanks!!!!!!!)
To get the whole thing back together, before I went to bed last night, I
removed the 3-wire (black/white/red) automatic-shutoff switch that caused
all this problem in the first place.
Then, I simply tied the two neutrals together and hooked the remaining
black and red to the original single pole single throw switch and put it
back together waiting for help from here at alt.home.repair.
I added three annotated pictures to the 14-picture set at
15. Simplified wiring just before final taping:
15. Testing with a screwdriver to see the light switch go on:
17. Putting the original single-pole single-throw switch back on:
Unfortunately, I must still have crossed neutrals because nothing I did
caused the GCFI to go live again.
GFCI can also protect other circuits via load terminals on
the back not just the plug outlets and its these wires which
probably go to the lights and are connected to a different
active or a different neutral or it might be possible the lights
have a ground fault ( moisture )
Take the load wire's off of the GFCI'S and see if they reset
Mark all of the wires so they can be replaced.
Donna, Thank you for the photos, but there seems to be too many wires and
variables to figure it out from a distance. It appears that there are too
many wires in some if not all of the electrical boxes. The splices on the
pigtails look like they are taped together. The two green twin circuit
breakers with the homemade handle tie should not have both circuits going
off at the same time. Overall everything looks as though it was done by
someone without much code knowledge and experience. The fact that you have
odd voltage readings when the light from the other bathroom is on tells me
that something may not have been wired correctly from the beginning. Is
there any reason why you cannot bring in an electrician to fix this? I
think that is what you need to do.
On Tue, 27 May 2008 07:51:34 -0400, John Grabowski wrote:
I do thank you for your help. I may very well need to bring an electrician
in. I've never done that before but it sure seems like I'm (almost) stumped
on this one. I just hate to let go (can you tell?).
It really irks me when I can't figure out a home repair on my own or with
help here. So, I may very well conclude that ... but I first want to
understand what is going on.
Bear in mind, the GCFIs were all working so whatever was wired to the
two-wire SPST switches before I put the three-wire automatic-shut-off
switches in was working properly (albeit I never tested the voltages).
I'm going to mull deeply over the GCFI information from Telestra to see if
I can understand it. At the moment, I realize I have "crossed neutrals" but
I need to re-read and re-read his explanation before I will know what to do
to resolve the problem.
I posted 17 well-annotated pictures of the situation at the slideshow
Donna, If I was to come over and work on this, my first step would be to
identify each conductor's function. Is the white really a neutral or is it
carrying juice to feed a switch? What are the red wires for? How does each
box and receptacle get fed? Which wires are the feed from the circuit
Get some numbers or white tape and start labeling everything. Draw a
diagram so you see what is happening on paper.
Don't be hard on yourself for not being able to figure it out. It doesn't
seem like a normal situation for one thing and for another, everyone has
limitations. Even the pros get stumped occasionally.
At the risk of labouring a point the GFCI has four wires
connected to it. Active and neutral from the house supply
which goes to the plug receptacles and load wires which
go to another protected circuit, Disconnecting these load
wires will still leave the plug receptacles LIVE.
The varying voltage is due to the fact that you have placed
the resistances of the light bulbs in series by mixing up
the loop wires to the lights and switches.
For example connecting the loop to the next switch to the
wire to the Bulb would cause the current to flow in series
through both light bulbs.
The way the circuit is wired up is Active to light switch
joined to active loop wire to next light switch. Neutral to
first switch joined to the neutral loop to the next switch.
Both switches now have a NEUTRAL and ACTIVE. The
two wires from the bulbs are now connected one to the
NEUTRAL and one to the SWITCHED ACTIVE.
A ground fault will trigger it and it may need to be rest [ After you
correct the ground fault ]
How are you measuring that voltage? If you are using a modern digital
meter, it likely it picking up induced power from wires that are close to
each other. If that is it, you would ignore than for this use as it is
little more than static electricity. (Note: it is not static electricity
however) It also could be a floating neutral, which means you have an
existing wiring problem.
All this and your questions and comments leads me to strongly suggest
that you hire a professional in this case to weed through all this and make
sure everything is properly done. A mistake here can be your last.
Making a shrewd guess i would say the installer brought
the wires from the GFCI into the backbox of the light switch to
connect to other outlets and take advantage of the holes made
for the light cables and these wires were never connected to
So you have to separate the unprotected circuit from the
protected circuit once this has been done the GFCI will reset
and the lights will go back to being a simple straightforward
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