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Intermittent tripping breaker

Discussion in 'Electrical Engineering' started by max, Mar 21, 2005.

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  1. max

    max Guest

    I am hoping someone can give me some insight as to where to look to
    solve a bizarre problem with a home circuit breaker that is tripping.

    Bulldog "Pushmatic" breaker panel.
    Yes, it's old, but it's been extremely reliable.

    About a week ago, a 20-amp breaker started randomly tripping
    in the panel. By "randomly" I mean it trips 2 or 3 times a day,
    with no apparent load on the circuit.

    I have traced the circuit. The wire runs from the panel to
    the basement. There, it goes to a single octagon box, and runs a
    pullchain light. Out of there, it goes to a receptacle, into which
    is plugged a gas oven (power for the oven light and control valve for
    the gas, no real load here). Also from that octagon, another
    wire goes to an outlet, and some basement overhead lights in other
    octagon boxes.

    And THAT'S IT.

    I replaced the breaker. Didn't help.
    I pulled all the boxes in the basement open, pulled OUT the fixtures
    to examine the wiring. Nothing is loose, nothing is skinned or shorted.
    I checked the voltages from hot to neutral, hot to ground, and neutral to
    ground, and it's all fine (120 v between hot and Neutral or hot-to-gnd,
    nothing between neutral and ground).

    I unplugged the oven, didn't help, so I know it's not that.
    I pulled the feed wire out of that first octagon box and capped off
    the wires, so the circuit was running NOTHING. It didn't trip after that.

    But if I connect it to anything else, I get this tripping problem.

    Oh, one more thing. I also pulled open the service panel, pulled
    the hot wire off the breaker, and inserted an ammeter. With the oven
    unplugged, I see zero current draw, which is right. If I turn on
    one light in the basement, I see about 1.2 amps, which is also about

    I am beginning to think that it's somehow related to another circuit
    in the house. But every single thing in the house works (we have gone
    to every room, turned on every light and appliance, and plugged
    something into every single outlet in the house. Everything works.

    It's almost like it's related to something that comes on and off by
    itself, like a thermostat, or the furnace hot water circulating pump,
    but I can't really correlate the tripping to those things either.

    Any brilliant ideas?

    --- Max
  2. SQLit

    SQLit Guest

    Have you tried meggering the circuit? Checking the insulation of the wiring.
    You will need to unplug everything to do this.
  3. max

    max Guest

    What do you mean "meggering"? Do you mean:
    1. Unplug everything from the circuit (including taking
    all bulbs out of the fixtures.

    2. Disconnect the hot wire at the panel
    3. See what the resistance is from hot to neutral and
    from hot to ground.

    Is that the idea? And make sure that the resistance is
    really really high, right?

    --- M.
  4. Roy Q.T.

    Roy Q.T. Guest

    Soundz to me like you have a Ghost taunting you }:)

    What gage is the wire that is attached to the circuit breaker ?

    What gage is the wire throughout the defective 20A circuit?

    * Is there a trough or splice box where several circuits converge past
    the panel & before the branch circuits ?

    Reads like you were thorough enough, but You've missed something, for

    That sort of problem occurs alot when a)you have an overload, or, b) a
    (Ghostly) bad neutral connection somewhere.Maybe the owner just likes
    having you around opening boxes & testing wires }:) Ask her if itz okay
    if you bring in an Exorcist to look into it ?

    Roy Q.T. ~ E.E.Technician
  5. Guest

    You have the basic idea. However, the resistances involved are normally
    so high (tens of megohms) that your garden-variety meter, powered by a
    1.5 V or 9 V battery, can't measure them. A meter called a "megger" is
    designed to measure high resistances by applying a voltage of 500 to
    1000 V or so. Some of them generate this from a normal battery and some
    have a hand crank you can turn.

    Also, I would disconnect all three wires (hot, neutral, ground) at the
    panel, and try all three pairs (hot-neutral, hot-ground,
    neutral-ground), before trying to measure resistance this way. If you
    do this, it won't hurt anything to try it with a normal meter, but don't
    be surprised if the meter reads "infinity" on all three readings.

    Some other ideas... when you replaced the breaker, it was with a brand
    new breaker, right? Something else you might try, if you have another
    breaker of the same rating in that panel, is to swap the circuits
    between the two breakers. If the same breaker blows, it's the breaker;
    if the other breaker blows, it's the circuit.

    Does it seem to be correlated with walking in a certain part of the
    house, or closing a certain door, etc? Movement of the house structure
    might be causing wires with marginal insulation to contact each other.

    Failing that, since it seems like you can follow the circuit pretty
    well, you might work along the chain, disconnecting parts of the
    circuit, like you did at the first junction box. After a while you can
    probably isolate it to a certain run of cable. At that point you can
    either yank that section of cable out to satisfy your curiousity, or you
    can disconnect the bad section and wire around it with fresh cable.

    Matt Roberds
  6. Check for corrosion or oxidation in the circuit breaker panel
    where the circuit breaker snaps onto the buss bar. You should
    turn off all power to tbe panel before doing this. A high
    resistance connection will heat the breaker and cause tripping.

    Bill Kaszeta
    Photovoltaic Resources Int'l
    Tempe Arizona USA
  7. Roy Q.T.

    Roy Q.T. Guest

    Say Max it just occured to me: if you haven't check out any motorized
    appliance Plate current waterpump, washer, fridge etc. the Overcurrent
    Protection on their branch circuit Circuit Breaker to which it is
    connected must be rated 115 -125% the branch circuits total load so you
    must take that into condieration when estimating your current values
    versus your circuit breaker/conductor ampacity.

    I think someone had mentioned it, when any motorized appliance or
    machine kicks on more than the running current is drawn and that may be
    a factor in your troubled circuit.The Ghost in The Machine];-) => Not
    all that connected to it (apparently under current values) but a
    Temporary Intermitent Overload created by an appliances Random kick off
    taking it past the circuit parameters.

  8. max

    max Guest

    The wire is #12, and it's a 20-amp breaker, so that's correct.
    As for any trough or splice box, no. The wire goes up out of the panel,
    into a crawlspace (which I've been in, and I can see all the wires
    coming up out of the panel). From there it goes down a wall,
    and into the basement, where I can see it. About 3 feet later,
    it goes to the first junction box with the pullchain fixture on it,
    and from there, it goes everywhere else in the basement that
    this circuit feeds (2 lights, and 2 outlets, one of which has the
    oven plugged into it).

    So, except for the 8 feet or so of wire going down that one wall,
    I can see every inch of the wire.

    As for an overload... even with this circuit fully loaded,
    there could only be about 4 amps of current on it (just a few
    lights and the oven control valve.

    I also plugged a big toaster oven into one of the basement outlets
    to see if anything "exciting" would happen when the circuit was under
    heavy load. Nothing happened (except the toaster oven came on and
    the elements heated up).

    Just today, I did note that the ground wire from the main service cable
    inside the panel wasn't quite tight (where the big cable goes into
    the big screw on the bus bar). I tightened this. About 10 years ago,
    we had a problem where the main breaker tripped a couple of times
    over a few days, and I noted then that the mains screws weren't quite
    tight (&@#@%^$ aluminum main wire!). No, there is no other aluminum in
    the house. Just the drop from the street pole.

    Anyway, after I tightened it, the breaker didn't trip all day today
    until just about an hour ago. I really thought I had found it.
    Although I did wonder why the loose ground would affect THAT particular

    --- Max
  9. max

    max Guest

    Yeah, I looked up "megger" on the web.
    But I have a good-quality meter that can measure up to
    10 megohms. Besides, if the resistance is a full megohm,
    I doubt I have an insulation problem.

    About the breakers... First, I swapped the wire over to
    another 20 amp breaker that was unused in the panel.
    It still tripped. However, wondering why there would be an unused
    breaker in the middle of a panel, I worried that maybe that
    one was no good (that's why it's unused) and they left it in there
    because they didn't have a blank and didn't want to leave a hole.
    So, I replaced the breaker in the original spot. And it still trips.
    The replacement was NOT new, though. Bulldog Pushmatics aren't easy
    to come by --- although I have since found a few places that have them
    for about $25 a piece.

    I think you're right. If I swap it with one of the existing 20-amp
    breakers that isn't tripping, that will eliminate the breaker from
    the equation once and for all.

    I haven't been able to correlate it with ANYTHING. It trips at all
    times of day or night. It doesn't seem to matter whether the house
    is warm or cold (furnace running during the day, or running less
    overnight). It doesn't seem to be affected by any activity (like
    being upstairs, downstairs, etc).

    Seeing as how it tripped with the lighting branch disconnected,
    or the oven receptacle branch disconnected, but not with BOTH
    disconnected, it certainly seems like it has to be the main wire
    from the panel, or something really weird in the house that's feeding
    voltage back onto this one circuit.

    I should have mentioned that although the house was rewired in the 1970s
    (no, it's no aluminum wire), it is over 100 years old, and there are
    still some unseen sections of knob and tube wiring in it, not to mention
    some insane wiring maneuvers that I probably haven't found yet (i.e.
    I've caught a few potential disasters over the years and fixed them,
    like 3-wire outlets with no connected ground, or a 20-amp circuit
    that went IN to a junction box but came OUT on a branch without the
    ground being connected, and my personal favorite, an extension cord
    in a cabinet that went into the floor, only to be wire-nutted onto
    the romex under the floor (no box, no NOTHING).

    However, and this is key, this particular circuit is nice clean new
    NM rubber-jacketed wire over its whole length. It does not have any
    potential for this other type of junk being in it.

  10. max

    max Guest

    Yup. Been inside every box. Nothing was loose, and nothing was
    touching anything. I even ran the circuit with every box pulled open
    (the porcelain pullchain fixtures pulled down out of their octagon
    boxes, and the receptacles and switches pulled out). Still tripped.

    I wondered about the clamps, or maybe even the steel staples that
    anchor the cable to the overhead joists in the basement. I'll have
    another look at those.

    Of course, this would be a lot easier if the damn thing would just short
    out altogether. Then I could disconnect things and find it. But it
    will run for 8-10 or more hours without a hiccup.

  11. max

    max Guest

    Not a bad idea. But since I've already swapped out the breaker,
    I was looking for that. Although this panel is old (from the 1970s)
    the inside is clean as a whistle. There isn't a blemish or spot of
    rust anywhere. The busses are clean and bright.

    thanks, Max
  12. max

    max Guest

    I have puzzled and puzzled about this. There is nothing motorized
    on this circuit. However, could a motor on ANOTHER circuit cause this?
    I keep wondering if the circulating pump for the hot water heating
    system could cause this (although that thing turns on and off
    a hundred times a day, and I've never caught the breaker tripping
    right when the pump goes on or off). I keep wondering if
    that motor could send a spike back to ground when it kicks off. But
    even if it did, I don't see how that would hit this circuit. The wiring
    isn't anywhere near each other (even though it's in the same room in
    the basement), and the spike would go back to the panel and to ground.
    I'd also expect it to affect other circuits as well.

    Remember, no other circuit in the whole house is misbehaving.
    -- M.
  13. John G

    John G Guest

    As someone has already said your good quality meter will NOT do what a
    MEGGER will do.
    A Megger will put 500 or 1000 volts between the test points and find
    breakdowns that the 1.5 or 3 volts in your good meter will never find.
    Do not forget to remove all the power before testing.

    Aside from all that you do seem to have a strange problem which after
    acutally changing the breaker will only be solved by breaking off every
    separate wire in that furher junction box till one of them proves to be
    the culprit.
  14. Roy Q.T.

    Roy Q.T. Guest

    pardon me: it doesn't seem like a motor Kick (On) overrload };-{) it
    does sound puzzling like you say. I came across a tuff pony like that
    once i'm not sure but I may have just rewired the affected zone.

    (*) There could be a Break in one of the New Conductor (sometimes
    handled too Roughly) that when energized is drawn together at the
    fracture, and when the circuit conductors relax (they do expand &
    contract) the fracture again disengages Causeing it to Trip ... you'd
    have to take a chance and rewire the affecting or affected
    length....test: disengage everything you know is good and put a
    temporary hookup to it (for the tenants convenience) from a circuit
    breaker in known good service spot and see if it will trip again (& from
    what configuration).[you probably have it narrowed down already] but,
    narrow down your branches until you isolate the affected conductor cable
    eliminate it, and redirect New cabling to the splice box remove the
    tempt hookup and VVuala ..... i hope :)

    just in case that test fails: recheck all your Buss lugz in every panel,
    the power company should attend to their meter you can say it's suspect
    & have it opened & check it with them.

    Electrical Circuits & Equipment are known to stop messing around when I
    enter a dwelling };-) with practice & determination (which you don't
    lack) they'll soon respect you too.


    ps: don't tell me ? it's stranded & can't fracture like that.....
  15. Roy Q.T.

    Roy Q.T. Guest

    Only guys I know have Meggers are Utility Linemen/Workers (if all fails
    call em) & Cable TV Trackers. If that was the only solution my goose
    would be cooked a long time ago.
  16. Anthony

    Anthony Guest

    Since you have disconnected the feed from the first junction and it did
    not trip the breaker, the problem has to be further down the line.
    Get a suitable length of 12/2 w/g romex for a test wire, unhook the feed
    at the first junction box, hook it into your new piece of wire. Go to
    your second box on the run, unhook the feed from the junction box coming
    into that box, hook your new wire in there temporarily. Wait for a trip.
    Keep jumping out one isolated leg (run) of the circuit at a time with
    your test wire. You will find your problem.
    There is an obvious problem (short) somewhere, and waiting until it
    becomes evident by itself may leave you homeless :/


    You can't 'idiot proof' anything....every time you try, they just make
    better idiots.

    Remove sp to reply via email
  17. max

    max Guest

    First, me say a big THANK YOU to all of you who have contributed
    your advice on this ugly breaker-tripping problem. I very much
    appreciate it.

    Here's where it stands.

    Recall, the breaker has been swapped with another one that happened to
    be unused in the panel, and with another one I had, which was not new.
    This didn't help.

    The feed from the panel goes to a junction box which feed only two
    branches that are plainly visible in basement ceiling. The breaker
    has tripped when EITHER branch is connected by itself. The only time
    I have seen it not trip is when the main feed wire was just capped
    off with wire nuts at the first junction box.

    I have tightened and checked everything in the main panel, including
    a slightly-loose screw on the main ground from the service cable.

    All branches disconnected at
    the first junction box, which I did before, and which many people have
    suggested. But a pigtail is spliced onto the feed
    wire there. I had tested it before by disconnecting everything
    and just capping off the feed wires, but that doesn't put any load
    on the circuit. It could be that the wire from the panel is
    bad after all, but only shows trouble if there's some load on it.
    So now I've got a light bulb on it all the time.

    I swapped the circuit in the panel with another breaker that is
    known to be working (had never tripped in its life that I know of.
    This eliminates the possibility that the spare breaker I tried in the
    panel was bad AND the replacement breaker I put in was also bad (it
    wasn't new).

    There's one more tidbit that might mean something to one of you
    out there. Let's call the problem breaker #6. Recall that the panel
    feed goes to a junction box, and then 2 branches go out of there --- one
    for some lights, and one for an outlet.
    I noticed today that on the lighting branch, I can read 3 volts between
    the hot wire and ground even though this branch is completely
    disconnected. I went down the panel, turning each breaker off/on in
    turn, and found that the 3 volts disappears when ANOTHER breaker is off
    (#12, just for conversation's sake).

    Cable for circuit #12 does go through the basement, and in a few places
    it is pushed right through the same hole in the floor joists with the
    cabling for circuit #6 (very bad practice, I know... wasn't my
    handywork). In fact,
    the two cables were jammed really right through the same hole
    in 2 spots.
    It's also true that if I put even the slightest load on this branch
    cable, (like an analog VOM), the voltage disappears.
    It looks to me like it's an induced voltage caused by the cables
    for the two circuits being so close together.

    As I plug things in or otherwise change the load on circuit #12, the
    induced voltage goes up or down (but never more than 3 volts).

    I drilled some new holes and rerouted the #6 cable so they are
    separated. After each place I did this, the "mystery" voltage dropped,
    until now it's down to about 200 millivolts. And no, I didn't find even
    the slightest nick or distress on the cables where I separated them.

    The breaker was tripping even when this branch was completely
    disconnected, so this can't be the problem.

    But... is this normal? Is it anything to worry about?

    --- Max

    And to tell you the truth, I'm beginning to think this is one of those
    problems that's being cause by MORE THAN ONE problem at the same time.
    I've had a few of those in my life, and they are always the worst.
  18. max

    max Guest

    Standard 20A non GFI Bulldog Pushmatic.
    The feed goes out of the panel, to a junction box with a pullchain
    light on it.
    From there, it goes out to only two branches. One is an outlet, and the
    other is just some lights in the basement (all octagon boxes with
    porcelain fixtures on them).

    The breaker will hold anywhere from 2 to 12 hours (approximately).
    Usually, it holds for 6-8 hours.

    When it trips, there is no way I can see to "reset" these like
    a "normal" breaker( i.e. a Square D, where you switch it all the
    way to the "off" position, and then turn it "on").
    These are just push on, push off devices. The only thing you can
    do is "push" it, and it clicks on (and "on" shows in the little

    If there is some special way I'm supposed to reset these, I'd sure like
    to know about it.

    Yes, while it's on, I definitely have tried pulling on things to see if
    I could expose a weak spot, bad connection, or short somewhere. I've
    had all the fixtures down out of there boxes, on, and bent and twisted
    them, and pulled on the romex cabling in the ceiling everywhere I can
    touch it. Nothing ever happens.

    Colors: Yes, all the blacks are hot, all the whites are neutral, and
    all the bare are ground. I've checked every one, in every single box,
    including the panel, with a meter. I've checked between hot and
    neutral, hot and ground, and neutral and ground. Everywhere I get
    Hot-Neutral (about 120v)
    Hot-Gnd (about 120v)
    Neutral-Gnd (zero, or a few millivolts at most)
    (All except for the one whacky branch, where I saw the induced voltage
    from circuit #12.)

    About another circuit interacting... that's kind of where I was going
    when I found the induction voltage from circuit #12. I put a meter on
    the circuit #6 hot wire and my wife cycled all the breakers. But the
    only thing I saw was that 3 volts, which fades the further apart you
    make #6 and #12 cables.

    On making this up... You can rest assured that I certainly am not.
    Problems like this are about as much fun as mystery plumbing leaks
    (don't get me started!) And it's been one terrific headache. I'm just
    glad it happens to be on a circuit that doesn't cause any disasters
    when it trips (i.e. it doesn't shut down our furnace or refrigerator
    in the middle of the day when nobody is home!)

    I'll let you know when I know something. Since I put everything back
    together this afternoon after separating the wires, I hung that pigtail
    light on the circuit (with the rest of it disconnected) for a few hours,
    and nothing happened. Now, I've got the branches hooked back up, and I
    did swap the breaker with a known proven working one from another
    circuit, so I'll know for sure whether the breaker has anything to do
    with it.

  19. tuna

    tuna Guest

    The cable in the wall goes down behind kitchen cabinets. Nothing has
    been touched or
    changed on that wall in the 16 years we've lived in this house. There
    is no place you could
    hang a picture, even if you wanted to.

    I should clarify that when I "swapped the two breakers" this last time,
    I did exactly what you
    suggest. I just swapped the hot wires on the breakers, and left the
    breakers right where they

    And it ran all day today, until tonight. It tripped right after an
    electric heater switched off 2 floors
    away (yes, on a different circuit, and not even one that runs anywhere
    near where this
    troublesome one runs in the basement). Of course, we turned the heater
    back on and off
    a million times, but the breaker won't trip again.

    Yep, I tightened every screw in the panel. All the neutral and ground
    ones in the ground block.
    All the hots on the breakers, and even gave a crank on the 2 main hots
    and the main
    ground (which is how I found the slightly loose main ground).

    About the incandescent lamp... I wouldn't know. Since this circuit runs
    stuff in the cellar,
    I would have to camp out there for 8-10 hours at a time with a light on
    to see what
    it would actually look like when it trips.

    This last time ran from about 2:00PM until 8:30 PM. 6.5 hours... which
    is pretty typical.

    So... once and for all, it DEFINITELY ain't the breaker. I guess it
    could be a squirrel or mouse
    chew, or something stupid like that, in that wall.
    When they rewired the house, I don't know exactly what they did. But
    they did tear
    the entire kitchen apart, and most likely ripped out all the old plaster
    to put up the drywall
    that's there now, plus the cabinets, appliances, etc. This was all done
    in the 1970s sometime.
    Yes, this wire has been there that long, untouched.

    It would take hours to snake a new wire down that wall and get it back
    to the panel,
    but I think it is possible. If they didn't staple it in the wall, I
    could even use the old wire to pull the
    new one through. But it it's stapled, I'll have to bore a new hole top
    and bottom and start
    fishing a snake through there --- joy --- been there, done that, don't
    really want to do it again.

    --- Max
  20. Roy Q.T.

    Roy Q.T. Guest

    Dang it ! Right ?

    look if this doesn't work send for an exhorsits Okay.

    Take the feed you describe off the panel & the 2 branch circuit wires at
    the junction box ( in short isolate the branch circuits from the feed
    from the circuit panel

    Now: with a separate run of cable use (10 Awg for this), reconnect the
    branches to the panel. Since you have the time :) wait for a trip as
    you've been doing. if it doesn't trip, attached the New Cable
    perminently with proper connectors and bushings to the Breaker Panel &
    Branch Circuit Junction box.

    If the problem persists and you decide not to re-wire the primary feed
    to the of Branch Circuits

    " Dominus Padre Voltbiscum " };-)

    Roy JPQT

    addendum: sometimes if you push the breaker in release it with a snap &
    push On again it may re-set if a healthy voltage is present.

    addendum II: what type of service conductors feed the house.
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