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  1. #1
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    Default Circuit breaker keeps tripping....how to proceed??

    We have an old house (circa 1950). There is one branch circuit with old-style NM cable (rubber/black paper insulation, no grounding wire). This circuit powers plugs/lights in the kitchen.

    Recently we plugged a 300W electric heater into the circuit, and the breaker tripped when somebody also ran an electric kettle plus some other appliances....no surprise there, since the load was probably over 15A.

    However, today the breaker tripped when only a couple of lights were turned on. This would be a load much less than 15A. That is new!

    Now I'm wondering about the integrity of the circuit itself....is it possible that running a very heavy load (even for a short time) caused some overheating of the wires, breaking down the insulation and causing a short that is now tripping the breaker?

    Is there any way I can test the integrity of the circuit itself without crawling up into the attic or ripping out plaster walls? What is the best way to proceed from here?

    Thanks in advance to the experts on this forum for their advice.

  2. #2
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    Default Re: Circuit breaker keeps tripping....how to proceed??

    Similar case here , home circa 1953.
    Every now and then I would have the microwave running and plug in the kettle ( knowing better ) bam circuit breaker trips.

    Now I'm sure this had happened many times before I bought the house though there was a fuse panel before I bought the place and haven't experienced or spotted any deteriated wiring as result.


    To say your circuit wiring may have become compromised because of that incident ..... maybe..... though it's more likely a connection at a wire nut might a problem.

    However .... I would be more inclined to start with the breaker itself.
    Take a known good breaker in the panel and swap it with the one that is tripping.
    This way you have an idea if it's the circuit or the breaker and where you have to concentrate the repairs.


    Just a thought.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  3. #3
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    Default Re: Circuit breaker keeps tripping....how to proceed??

    Circuit breakers can be a little more complicated than they appear. They’re supposed to “pop” when amperage exceeds a normal or “rated level.

    The evil twin of amperage is surge current. Calculating simple amperage is fairly easy. It’s watts divided by voltage. A 300-watt appliance on 120-volt circuit conducts about 2.5 amps in a consistent manner other than when surge current happens. Surge current happens when the appliance starts up and suddenly draws enough amps start up to do what it needs to do to get started. And, surge current is normally far more than normal current draw. Generally, 10 to 15 times normal draw. It’s like a racecar. It takes much more fuel to go from zero to 60mph than it takes to maintain that 60 mph over the same distance.

    Circuit breakers operate with an electromagnet. As we all learned in elementary school, an electromagnet works by coiling wires around a metal bar and then passing a current through the wires and that creates magnetism in the bar. More current passing through the wire makes a greater level of magnetism. In a circuit breaker, when the current gets to a high enough level, the magnet is strong enough to move the switch to a closed position.

    And that’s where the problems begin. As my electrical engineer friends tell me. Once that bar is magnetized, it tends to hold more magnetism than it did before so it takes less current to raise it to a level of magnetism than it did before to trip the circuit. So, over time, a circuit breaker becomes easier to trip then it did before. So, essentially, they wear out over time because they always have a current passing through them which maintains that previous level.

    Rule of thumb is; Replace a circuit breaker when it pops, because it will never be as reliable as it was when it was new and will continue to “weaken” over time.

    Also, surge current can possibly weaken wires so that’s a major reason to be concerned when not replacing a breaker.
    If I only knew what I was doing!

  4. #4
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    Default Re: Circuit breaker keeps tripping....how to proceed??

    I disagree with a couple of things mentioned above . Not all molded case circuit breakers use an " electromagnet " , most use a bimettalic element or a combination of the two and
    thus residual magnetism isn't usually an issue . Also , I wouldn't replace a circuit breaker just because it tripped once .

  5. #5
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    Default Re: Circuit breaker keeps tripping....how to proceed??

    Quote Originally Posted by djohns View Post
    I disagree with a couple of things mentioned above . Not all molded case circuit breakers use an " electromagnet " , most use a bimettalic element or a combination of the two and
    thus residual magnetism isn't usually an issue . Also , I wouldn't replace a circuit breaker just because it tripped once .
    Yep .... I agree
    "" an ounce of perception -- a pound of obscure "
    - Rush

  6. #6
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    Default Re: Circuit breaker keeps tripping....how to proceed??

    Quote Originally Posted by rickpantel View Post
    We have an old house (circa 1950). There is one branch circuit with old-style NM cable (rubber/black paper insulation, no grounding wire). This circuit powers plugs/lights in the kitchen.

    Recently we plugged a 300W electric heater into the circuit, and the breaker tripped when somebody also ran an electric kettle plus some other appliances....no surprise there, since the load was probably over 15A.

    However, today the breaker tripped when only a couple of lights were turned on. This would be a load much less than 15A. That is new!

    Now I'm wondering about the integrity of the circuit itself....is it possible that running a very heavy load (even for a short time) caused some overheating of the wires, breaking down the insulation and causing a short that is now tripping the breaker?

    Is there any way I can test the integrity of the circuit itself without crawling up into the attic or ripping out plaster walls? What is the best way to proceed from here?

    Thanks in advance to the experts on this forum for their advice.
    Are either of the locations you tapped for either of these appliances and/or the circuit breaker which tripped formerly one of the multi-wire circuits that you recently seperated to individual branch circuits (one of your former posts)?

    Are any of these receptacles one that you recently replaced (formerly two-slot receptacles) when you were inquiring about replacing non-grounding type receptacles with three-slot type grounding ones? were the original two-slot receptacles the polarized type or non-polarized type (one slot fin wider than the other)?

    Is the "offending" device - space heater - the one that you were inquiring about replacing the cord with a three-prong type? (modern portable space heaters are required to have a fusable cord or plug).

    Do you have GFCI receptacles installed in the kitchen or earlier in the circuit?

    Is your armored cable or somewhere in the circuit intermittantly grounded say to a water pipe?

    Any of the areas near your former pin-hole leaks near copper water pipes or where water might travel from a pin-hole leak in a copper water pipe (perhaps new area) anywhere near your BX?

    A nail penetration, lots of possiblities. Most common a wiring error. Very common to have spilt circuits in kitchens especially with your history of multi-wire circuits.

    What type of panel do you have? how old is it? Do hope it isn't a split bus type with a history of problems.

    And yes, the old rubber wire insulation can dry out and be brittle and crack, fall off. Since there may have been re-routing activity or the cable itself disturbed there could be a problem. A short, arc, etc. may not have taken place in an accessible location.

    I suggest with your history of problems, concerns, and activities you might be best served if you acquired the assistance of an on-site master electrician to do some trouble shooting and to examine the safety of your system. 40 years is beyond the original "useful life" of vintage bx (originally calculated at 25 years). You may have made a wiring error, there could be a compromise, something may have been damaged - too many factors. It is often most difficult to edit, review, and troubleshoot one's own work when one has a pre-set collection of assumptions about the quality and correctness of one's own former actions.

    Kitchen lights and small appliances shouldn't be on the same circuit - and shouldn't have been back in the 50s either, don't think that was allowed back then even in Canada.
    Last edited by Blue RidgeParkway; 12-28-2008 at 10:33 AM.

  7. #7
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    Default Re: Circuit breaker keeps tripping....how to proceed??

    Quote Originally Posted by Blue RidgeParkway View Post
    Are either of the locations you tapped for either of these appliances and/or the circuit breaker which tripped formerly one of the multi-wire circuits that you recently seperated to individual branch circuits (one of your former posts)?

    Are any of these receptacles one that you recently replaced (formerly two-slot receptacles) when you were inquiring about replacing non-grounding type receptacles with three-slot type grounding ones? were the original two-slot receptacles the polarized type or non-polarized type (one slot fin wider than the other)?

    Is the "offending" device - space heater - the one that you were inquiring about replacing the cord with a three-prong type? (modern portable space heaters are required to have a fusable cord or plug).

    Do you have GFCI receptacles installed in the kitchen or earlier in the circuit?

    Is your armored cable or somewhere in the circuit intermittantly grounded say to a water pipe?

    Any of the areas near your former pin-hole leaks near copper water pipes or where water might travel from a pin-hole leak in a copper water pipe (perhaps new area) anywhere near your BX?

    A nail penetration, lots of possiblities. Most common a wiring error. Very common to have spilt circuits in kitchens especially with your history of multi-wire circuits.

    What type of panel do you have? how old is it? Do hope it isn't a split bus type with a history of problems.

    And yes, the old rubber wire insulation can dry out and be brittle and crack, fall off. Since there may have been re-routing activity or the cable itself disturbed there could be a problem. A short, arc, etc. may not have taken place in an accessible location.

    I suggest with your history of problems, concerns, and activities you might be best served if you acquired the assistance of an on-site master electrician to do some trouble shooting and to examine the safety of your system. 40 years is beyond the original "useful life" of vintage bx (originally calculated at 25 years). You may have made a wiring error, there could be a compromise, something may have been damaged - too many factors. It is often most difficult to edit, review, and troubleshoot one's own work when one has a pre-set collection of assumptions about the quality and correctness of one's own former actions.

    Kitchen lights and small appliances shouldn't be on the same circuit - and shouldn't have been back in the 50s either, don't think that was allowed back then even in Canada.
    That's incorrect.
    It was common back in the day to find kitchen light and counter receptacle tied into the same circuit feeding other rooms as well ..... unlike current codes.
    You would find only 2 or 3 general circuits feeding the entire home.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  8. #8
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    Default Re: Circuit breaker keeps tripping....how to proceed??

    it was more common to have a few lighting only multiwire circuits for the home's footprint, and several multiwire receptacle circuits serving several rooms and a multiwire circuit serving split receptacles in the kitchen.

    not going to debate with canuk who often makes unsubstantiated statements like that, the historically common practice of employing multiwire circuits, nor split receptacles serving kitchens in the 50s with you canuk, rickpatel has indicated in prior posts that his home was originally multiwire circuits not individual branch circuits. just because canuk has claimed multiwire circuits were not common in the 50s also as well as split receptacles in 50s kitchens; nor the common historical practice of dedicated lighting circuits doesn't make that so. that canuk reamins unfamiliar with those most common historical practices is not surprising.

    rickpatel, I noticed on another post string you posted on the same day you created this one, you indicated that the only remaining bx wired circuits in your home you have installed arc fault breakers, so since you refer to this circuit as having the old bx cable - and the COPD is also supposedly an arc-fault (and not a GFCI breaker with an arc fault between the panel and the remainder of the circuit ) and you are operating small appliance (kettle) in the kitchen on this circuit and a space heater (considering your other posts on revamping or recording a portable space heater almost 20 years old), I find that telling.

    Quote Originally Posted by rickpantel View Post
    Neun:

    I don't know if you are still following this thread that you started. I have the same problem that you do....older wiring buried in plaster walls and very difficult to replace.

    I replaced as much as I could and brought the accessible circuits up to standard. Where I could not easily get at the older wiring, I put the entire branch circuit on an Arc-Fault Circuit Interrupter (AFCI) instead of a standard breaker. At least that way, if arcing occurs in the circuit, then we have a greater chance of interrupting the power before a fire occurs. You can also split up some of the older circuits that have multiple branches....at least the electrical loads are reduced on the circuits that have older wiring.

    Hope this helps.
    P.S. it is also telling that most toasters, electric kettles, etc. use a non-polarized plug, does yours?
    Last edited by Blue RidgeParkway; 12-28-2008 at 01:15 PM.

  9. #9
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    Default Re: Circuit breaker keeps tripping....how to proceed??

    Quote Originally Posted by Blue RidgeParkway View Post
    it was more common to have a few lighting only multiwire circuits for the home's footprint, and several multiwire receptacle circuits serving several rooms and a multiwire circuit serving split receptacles in the kitchen.

    not going to debate with canuk who often makes unsubstantiated statements like that, the historically common practice of employing multiwire circuits, nor split receptacles serving kitchens in the 50s with you canuk, rickpatel has indicated in prior posts that his home was originally multiwire circuits not individual branch circuits. just because canuk has claimed multiwire circuits were not common in the 50s also as well as split receptacles in 50s kitchens; nor the common historical practice of dedicated lighting circuits doesn't make that so. that canuk reamins unfamiliar with those most common historical practices is not surprising
    Hmmm .... considering the home I live in is from the 50's era has a basement light , back door interior light , back door exterior light , kitchen light , kitchen counter receptacle ( not split ) , kitchen wall plug , clock receptacle , dining room receptacle , dining room light , front door interior light , front door exterior light all on one circuit ..... which is original.

    I've never claimed shared neutral ( multiwire ) are not common in homes of this vintage ..... considering I live in one that has this type.

    Regardless if they are part of a shared neutral ( multiwire) configuration all these devices are still on one circuit.

    Considering the dozens of homes I've been involved with and the thousands of homes wired this way ..... I guess they don't exist .... according to Blue Ridge Parkway.

    Once again you have have shown you don't know what you are talking about.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  10. #10
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    Default Re: Circuit breaker keeps tripping....how to proceed??

    Quote Originally Posted by djohns View Post
    I disagree with a couple of things mentioned above . Not all molded case circuit breakers use an " electromagnet " , most use a bimettalic element or a combination of the two and
    thus residual magnetism isn't usually an issue . Also , I wouldn't replace a circuit breaker just because it tripped once .
    I agree with the disagreement as well.
    And changing out a breaker would be a reach to me as well.
    And just to hijack the post, would the new breaker have to be an AFCI or would it be grandfathered?
    Last edited by Ernie_Fergler; 12-28-2008 at 02:46 PM.

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