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tuften

live wire with circuit off

tuften
9 years ago

Have a 1929 cape with steam heat and bx cable behind plaster
and lath walls.Decided to replace an outlet right behind the cast
iron radiator because it wasn't holding the plugged in wires any
more from years of heat.The outlet is feed power from a jbox just
below in the cellar and is the first outlet from the fuse #4.After killing the power to the outlet and disconnecting its leads from the
fuse I found that the duplex still had power. 120v neutral to grd,
120v hot to grd but 0v neutral to hot.I then shut off all the other
fuses one at a time until the duplex had no power.This happened
when fuse#5 was tripped.I then tried to figure what on fuse#5
could be feeding power to fuse#4 when I remembered we had our kitchen redone 5 yrs ago by an electrican and at that time
the kitchen light was on fuse#4.He remodeled the lighting to 4
ceiling recessed lights and 2 under cabinet lights and put them all on fuse#5.I traced his wiring to a small screw in type fuse subpanel in the cellar ,this subpanel got its power from
fuse#5 at the main.When I pulled the wires for the kitchen lighting from this subpanel I had no more voltage back feeding(if correct) to the dulpex on fuse#4.What do you think
the problem is here,did he some how tap into the other circuit
without knowing.Its been 6yrs wired like this and we have had
no electrical issues at all come up.Your thoughts are greatly appreciated

Comments (12)

  • Ron Natalie
    9 years ago

    How are you measuring this? Most digital meters these days are really high impedence and will read very small currents from long runs (especially disconnected wires) due to inductive coupling between the wires. You might want to use a tester with a bit more impedance (like a light bulb).

    My guess is that you have an OPEN ground. by the way.

  • tuften
    Original Author
    9 years ago

    after I killed power to the outlet and removed the wire nuts from the lines in the jbox I put a 2 prong tester across the neutral and
    hot lines connecting the duplex to the # four fuse and got 0v as i should,then using pliers I untwisted the hot lines ok fine,as soon
    as I touched the neutral lines sparks came off the pliers .I shut off
    the main to get the neutral wires separated put the power back on and proceeded to test the wires from the duplex with tester
    and it lit up neutral to grd and hot to grd but not neutral to hot.I
    then used a fluke meter set to alt volts and got the readings in my first post.How would a open grd cause this if everything clears up when I trip fuse # 5 from another circuit.Thanks for the response.

  • joefixit2
    9 years ago

    put the neutrals back together and check neutral to ground again with fuse #4 off and #5 on tell us what it reads. Also check hot to neutral again with the neutrals connected together and fuse #4 off, #5 on and report back.

  • tuften
    Original Author
    9 years ago

    To do that I will reestablish the original condition and hook back up the kitchen lighting controlled by fuse#5 and get back late today,in work now,thanks

  • tuften
    Original Author
    9 years ago

    With all neutral and hot leads connected this is what I get

    4off 5on hot to neutral = 0v
    hot to grd = 0v
    neutral to grd = 0v

    4on 5off hot to neutral = 120v
    hot to grd = 120v
    neutral to grd = 0v

    4on 5on hot to neutral = 124v
    hot to grd = 124v
    neutral to grd = 0v

    the outlet(duplex) in question on fuse 4 has a hot and neutral
    wire spliced into the hot and neutral wires that are screwed
    into the receptacle.These wires go upstream to a wall switch
    for the porch then to an over head pull chain light in another
    room and after that I don't know

    Last scenario all wires disconnected at jbox for fuse4 and
    testing just the neutral and hot wire from
    the receptacle to the jbox here is the
    problem

    4off 5on hot to grd = 116v
    hot to neutral = 0v
    neutral to grd = 116v

    thanks for any help.


  • joefixit2
    9 years ago

    In the old fuse box, by any chance are the neutrals fused? They usually ran a neutral wire up the middle and a row of fuses just for the neutrals.

    Here is a link that might be useful: fused neutrals

    This post was edited by joefixit2 on Tue, Oct 28, 14 at 0:06

  • tuften
    Original Author
    9 years ago

    here is a picture of the fuse box.Cable coming in on lower left is fuse 5 from the main.Upper right ( black and white wires) are the
    wires the electrician installed for the kitchen lights.The hot went to the lower left fuse and the neutral went to the lower right fuse.As I said before when I removed these wires the problem at the receptacle went awayThe other cables go to an upstairs light and a door bell transformer.

  • bus_driver
    9 years ago

    Time at the moment does not provide for reading all the previous posts. But it is possible that a neutral has been used for more than one circuit and the other circuit is still live.

  • joefixit2
    9 years ago

    I am almost certain the neutral was shared but I can't explain why he is getting 120 from hot to ground but not hot to neutral unless the neutrals are opened during this test, which made me think about fused neutrals.

    This post was edited by joefixit2 on Tue, Oct 28, 14 at 9:24

  • tuften
    Original Author
    9 years ago

    Does this condition pose as a fire hazard or possible electrocution if conditions were right because i have reconnected all wires so my wife can have kitchen lights and the outlet is used for the pc.But before that I tried another test, I tripped fuse 4 and 5 and removed the hot and neutral from the duplex going to fuse 4 and the outlet tested dead as it should.I turned fuse 5 back on which controls the kitchen lights and had my wife switch the light switch on and off and this is the readings I got at the duplex.Lights never came on during this test

    switch on hot to grd = 116v
    neutral to grd = 116v
    hot to neutral = 0v

    switch off hot to grd = 5.6v
    neutral to grd = 5.6v
    hot to neutral = 0v

    As always thanks for your time.

  • joefixit2
    9 years ago

    with the switch on power from switch 5 goes to the lights but they can't work because you opened the neutral path. You will see line voltage on the neutral because it is feeding thru the lamp filaments. As soon as you re-connect the neutral path the lights will come on and the voltage will drop to zero because it is now at ground potential. It is obvious that circuit 5 is using circuit 4's neutral, but how and why and if it is proper or not is not easily figured out over the internet, might be time to call in a pro.

  • tuften
    Original Author
    9 years ago

    thank you .I will pull out both light switches and trace where
    the neutrals go,or as I read at another site this situation is
    safe as long as all the neutral wires are secured, then I will leave it alone