Voltage not adding up

Discussion in 'Electrical and Wiring' started by Smontagu, Oct 13, 2013.

  1. Oct 13, 2013 #1

    Smontagu

    Smontagu

    Smontagu

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    15 year old house.
    No other electrical issues known.
    Plug and switch not used often.
    Wanted to add an outlet and ran into this problem.
    Disconnected plug so it can be ruled out.
    Replaced switch to rule it out, same problem.
    Switch on:
    0v at switch
    0v hot-ntrl
    120v hot-grnd
    120v ntrl-grnd

    Switch off:
    98v at switch
    98v hot-ntrl
    120 hot-grnd
    12v ntrl-grnd

    Other switches on the circuit measure:
    120v hot-ntrl
    120v hot-grnd
    >1v ntrl-grnd
    They are not effected by the switch.

    Not sure what to do?
     
  2. Oct 13, 2013 #2

    Smontagu

    Smontagu

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    The switch goes to a blower for the fireplace that is not working now. Not sure why that is.
     
  3. Oct 13, 2013 #3

    Smontagu

    Smontagu

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    I meant other outlets on the circuit measure not other switches. Also the switch is normally off. Both the fan and the outlet used to work.
     
  4. Oct 13, 2013 #4

    JoeD

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    Are you really measuring hot to neutral or are you measuring black to white, both of which are connected to the switch. Those voltage readings are correct a switch loop with no neutral in the switch box.
    If there really is a neutral (white not connected to switch) then you have an open neutral some where on the circuit.

    Tell us everything about what you did to add the new receptacle.
     
    kok328 likes this.
  5. Oct 13, 2013 #5

    Smontagu

    Smontagu

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    Okay so I don't think the switch is involved. The switch is to a fireplace fan. When I measured the "switch" there was only one measurent, from hot to hot across the switch. When I say hot I mean black. When I say neautral I mean white. When I say ground I mean exposed copper wire.

    The first measurement is across the switch. The other 3 measurements are at the outlet. I was not clear sorry.

    When installing the new outlet two things happened. First I had to drill a hole in the 2x4 behind the drywall, not easy. Second when I was cramming the outlet back in the box I did not tuck the ground wire away well enough as the breaker tripped when I turned it back on. I adjusted the outlet in the box and it was fine after that.
     
  6. Oct 13, 2013 #6

    Smontagu

    Smontagu

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    Also the switch only has two attachments for the black wires. The white and ground wires ae just straight attached with a twist carrot tops. In my mind when the switch is off the reading should be open or 120v. If the switch is on it should be closed and read 0v. Not sure why there is 98 and 12 which only equal 110? Where did the other 10 volts go???
     
  7. Oct 14, 2013 #7

    Smontagu

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    I removed some drywall and confirmed I did not drill into any cables.

    I disconnected the switch completely. There are three wires. The supply line, a cable to the outlet I am having trouble with, and a cable to the fireplace fan.

    When the switch was wired the fan was on one side and the supply and outlet were on the other side.

    Now the supply to the switch with everything disconnected is:
    120v blk-grnd
    20v wht-grnd
    70v blk-wht
     
  8. Oct 14, 2013 #8

    kok328

    kok328

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    Listen to JoeD, I think he is thinking the same thing as I.
    You can't measure voltage through the switch unless you are measuring the in/out to neutral or ground. You most likely have a switch leg to the blower motor in which case both black & white are hots. You have to wire it based on voltage not color.
     
  9. Oct 14, 2013 #9

    JoeD

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    OK so if understand you properly there are two black and two white wires in the switch box.
    You measure zero volts from black to white wire and 120 volts ground to black wire.

    You have an open neutral somewhere on the supply circuit. It could be in a working device.
    Measuring across a switch is not useful.
     
  10. Oct 14, 2013 #10

    Smontagu

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    Okay forget everything I said before here is what I have...

    A switch box with 3 cables going in to it. The switch is removed.

    Cable 1- supply
    Measurements are
    120v blk-grnd
    20v wht-grnd
    70v blk-wht

    Cable 2- goes to mulitiple outlets
    Measurements are
    All 0v

    Cable 3- goes to fire place fan
    Measurements are
    All 0v

    When the switch box was connected the three ground wires were rabbit eared together. The 3 white wires were rabbit eared together. On one side of the switch was the fan black wire, on the other side was the supply and cable to the outlets.

    What are the possible causes for having low voltage readings (70volts) from the black to white wires, and having a 20 volts white to ground reading.
     
  11. Oct 14, 2013 #11

    kok328

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    Cable 1, open neutral
    Cable 2, open hot
    Cable 3, open hot
     
  12. Oct 14, 2013 #12

    bud16415

    bud16415

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    Taking the switch out was a good idea and isolating everything. As you would think the two loads won’t have anything on them cable 2 and 3. You should measure 120 v from black to white and from black to ground on cable 1. The black wire is the hot wire and the common is white. You shouldn’t be getting voltage readings of anything except zero and 120 so these 20 and 70 volt readings are not right.

    What type of meter are you using and on what setting on the meter?

    If those readings are correct you have to chase the problem back down that cable to where it comes from. If you have anything you can use as a test load like a light bulb and do it safely you could test at each set of wires and see what the bulb does. If you have the low voltage you say you will see a very dim light at the low voltage. I keep a refrigerator socket with a rough service bulb in my meter box with a set of test leads attached and it’s quite handy for stuff like this.

    Likewise I have a power lead that’s fused that I can plug into a good circuit and power up something like your fan cable just to make sure those cables are working the way they should.
     
  13. Oct 14, 2013 #13

    kok328

    kok328

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    Bud, on a switch leg with the switch removed, you will have 0 volts between black & white, white & ground, black & ground.
     
  14. Oct 14, 2013 #14

    bud16415

    bud16415

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    From his last post he said he had 3 cables coming into the box number 1 was the power for the circuit and 2&3 were loads one being a fan of some kind and the other an outlet box or something like that. If you remove the switch I was saying the feed into the box cable one would have power to it. It sounded like the power then went straight to the outlet and thru a switch to the fan. That was my take on it anyway. Taking the switch out should leave everything down stream dead.

    The other method would be having the power originate at the device and then come to the box to be switched it didn’t fit his scenario as well I thought.

    He didn’t mention odd voltages around the rest of the house. Or things not working just this one circuit. Strange voltages make me thing of a missing ground also. Maybe I totally misread his problem I will have to go back and read it from the beginning. I started where he said don’t pay any attention to all the above.
    :eek:
     
  15. Oct 14, 2013 #15

    kok328

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    missing ground shouldn't cause low voltage problems. At this point, the OP has us all confused.
     
  16. Oct 15, 2013 #16

    JoeD

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    Like I said back in post #4 and #9 you have an open neutral on the supply cable.
     
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