Neutral drops out in circuit.

Discussion in 'Electrical Forum discussion & Blog' started by Homeownerinburb, Jan 21, 2012.

  1. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Hey guys,

    So more fun and games at the new ranch.

    Most of the house is wired with conduit, with a three wire circuit.

    On one of those three wire circuits, the neutral has failed somewhere along the line. Several items closer to the panel function, but most of the system has live hots but the volts from the hot to the neutral looks to be about 30v.

    Clearly the neutral has failed somewhere. I dread needing to crawl under the house, but I'll do it if I must.

    But does anyone have some clue as to where I am likely to find the fault?

    I own a small air compressor. I have in the past used this to pump air down conduit, which seems to tell me where the conduit goes.

    If I can find one box that has a valid neutral and the next box that does not, then obviously I will be trying to pull fresh wire to replace it.

    But how to find it? Sounds very tedious.
  2. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,307
    Location:
    Houston, TX
    Is that 30 Volts that you are measuring under load, or no load ?

    How are you taking your measurement, and what with ?
  3. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    No load, I'd expect it to run to nothing with a load.

    I own a cheap multi meter. I read from the hot that gave me a solid 120v to ground, and found from hot to neutral 30v.
  4. drick

    drick In the Trades

    Messages:
    392
    Multimeters,especially the cheap ones, are notoriously bad at giving accurate voltage readings in cases where there is no ground or a weak ground, so yo could have 30v or 90v or who knows what. You can still use it, but be forwarded.

    Since you still have the 120 volt leg you are in luck. First mark all the non working outlets with a piece of electricians tape or whatever so you know which they are. Next get a 120 volt reading between hot and ground on one of the nonworking outlets and then turn off your circuit breakers one at a time until you determine which circuit the nonworking outlets are connected to. Finally turn off all circuit breakers except the circuit for the nonworking outlets. Locate the remaining working outlets in the house and also mark these with a piece of tape. Electricians NORMALLY wire devices in a logical order, so your problem is most likely between the last working outlet/ light switch (that being the one furthest from the electrical panel on that circuit) and the closest nonworking outlet to it.

    Most of the time it turn out to be a problem with the last working device or a bad splice in a junction box (2+ gang light switch boxes are always a good place to look for a loose neutral) and not a bad wire, so look for those thing before pulling a new conductor.

    -Rick
    Last edited: Jan 21, 2012
  5. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,249
    Location:
    Land of Cheese
    Drick, that is one of the most logical and explanatory posts I've seen in awhile. Thanks for taking the time to put it here.
  6. lumpy1974

    lumpy1974 New Member

    Messages:
    3
    Location:
    San Jose, CA
    Yes alot of time the problem is in the working outlet ,switch.also belive it or not if you have burnt
    Wires the screw holdiing the cover on will appear rusted do to the heat from the wires coiking
    In the box.once you find this problem be good to inspect outlets,switchs,light fixtures,even install
    New devices like a commercial grade device.the problem is the connections loosen up over time
    Or circuit overloads that is what you can check for overloads.maybe cuurent check at panel also the connection
    In panel tighten screws call electrcian for panel if you think you need help in breaker box
  7. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,307
    Location:
    Houston, TX
    What do you get from Ground to Neutral ?
  8. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Mystery solved!

    The handyman hired by the seller installed several GFIs...........

    One serves the laundry closet. Why a GFI in a laundry closet?

    Get this: That outlet is in a back to back outlet, with another receptacle in the dining room. It is a three wire circuit..... And what do you suppose? There were three hots and three neutrals that needed to be lashed together...... And the handyman fed half the house on the load side of the GFI. So it tripped, cut off the hot for all that was down stream of that circuit, and the neutral that that circuit and it companion shared. Which explains why I saw 120v on one circuit, of course, and why I had no return on the neutral.

    Look out for those handymen! How many different elements of the electric code do you suppose he violated?
  9. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Rick,

    Good stuff. I will try to remember all that.
  10. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,811
    Location:
    Cave Creek, Arizona
    quote; Finally turn off all circuit breakers except the circuit for the nonworking outlets. Locate the remaining working outlets in the house and also mark these with a piece of tape

    Wouldn't it be more logical to just test which outlets, in addition to the non-working one, are not live when THAT circuit breaker is off, rather than turn everything else off and see which ones are still functional?
    I once had a customer whose garage freezer outlet failed and spoiled everything. They could not get it to work so they ran an extension cord to it. When I was there doing something else I asked them the reason for the extension. When they told me, I told them that they had a GFCI somewhere that had tripped. They said they had reset all of them and it still didn't work. I checked the entire house and found the GFCI outlet under a bench in their bathroom. They had never seen it or even knew it was there.
  11. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,307
    Location:
    Houston, TX
    The wires should be marked.

    Sounds like it is wired wrong.
  12. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Oh, it certainly was wired wrong. It was in a box that ran from one side of the wall to the other, and had an outlet at both ends. The three wire line entered, and the red line and neutral exited to go to a counter outlet in the kitchen. That is two white wires and two red. These were wired to the line side of the GFI. Without a pig tail for the neutral. Then the white and red going to the outlet on the opposite side of the wall. The blue wire entering with the line just crossed, split down two other conduits, and these of course were paired with the neutral, and the red ran down one of the conduits as well.

    So when the GFI tripped, the neutral and the red hot were cut off, but the blue hot carried forward.

    Needless to say, I made up some pigtails and deleted the GFI. Don't need a GFI in a laundry serving the equipment, and it is down near the floor, so if it did trip, one would need to move the equipment to reset it.
  13. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,307
    Location:
    Houston, TX

    Good that you figured it all out.

    Having a GFI on anything that uses water, and may leak, is not a bad Idea. If it is wired correctly.
    Last edited: Jan 23, 2012
  14. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    OK, but the GFI should be accessible.
  15. drick

    drick In the Trades

    Messages:
    392
    Yes it would. My Bad.
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