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Using A Circuit Breaker As A Manual Switch

Discussion in 'Electronic Basics' started by Bret Cahill, Feb 16, 2013.

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  1. Bret Cahill

    Bret Cahill Guest

    How many times can you flip a 30 Amp CB on and off before it wears
    out? Say you as gentle as possible with the switch.


    Bret Cahill
     
  2. Tom Biasi

    Tom Biasi Guest

    Different manufactures have different specs. What do you mean by
    "gentle"? Will you whisper sweet things to it while you switch a 30 Amp
    load on and off?

    Tom
     
  3. Guest

    I believe it's called an "switch" or 'S' rating. AFAIK, no
    residential breakers have a switch rating.
     
  4. Bret Cahill

    Bret Cahill Guest

    How many times can you flip a 30 Amp CB on and off before it wears out?
    How would you know w/o a test, i.e., a short with a known resistance?
    Maybe nothing ever went wrong in your shop and the CBs still worked
    great as manual switches but had, over the years, been altered as far
    as the amperage that shut them off?

    A shop would be the last place to offer as evidence as the "do
    everything within specs" mentality prevails. Much more compelling
    would be the dtisy residential situation test.

    The thermal CBs that Square D introduced in 1935 took awhile to for
    the bimetalic strip to heat up and pull away from a contact. They
    were replaced starting in 1940 with faster acting magnetic CBs.

    All the testing and innovation took place at the plant.

    But you never hear of electricians advocating anyone going around
    testing installed CBs for safety.

    This is similar to the idiot light problem. Supposing the idiot light
    has burned out?


    Bret Cahill
     
  5. Mr Ron

    Mr Ron Guest

    Here in the UK AFAIK there doesn't seem to be any way to test them. I had a
    brocken socket to be replaced and couldn't find the breaker. We tried the
    method of shorting the socket to earth to trip it. The wires just fused &
    sat there live.
    We eventually found the breaker at the other side of the store & had to
    replace with a derated one because the resistance of the circuit was too
    high.

    Ron
     
  6. mowhoong

    mowhoong Guest



    Last week my office's 30 years air con switch (single throw 20A ) breakdown, it was Mk brand , I manage to brough one balance stock from a shop at thirty six dollar and it was make in UK during 2009. The seller said you can save cost by using MCB as a switch and it is very commom. BTW a china make unmark rating wall switch only cost one dollar fifty cents only, sure notto use for air con.
     
  7. Bret Cahill

    Bret Cahill Guest

    But you never hear of electricians advocating anyone going around
    What would you need besides an amp meter and some resistors?
    That should be proof that the CB was no good.


    Bret Cahill
     
  8. Sjouke Burry

    Sjouke Burry Guest

    Your wiring needs replacing, a short-circuit should blow even a breaker
    of double that spec.
    Or you can wait until the house burns down.....
     
  9. Sjouke Burry

    Sjouke Burry Guest

    Perfect, those China breakers. They make the house burn down very nicely.
     
  10. Bret Cahill

    Bret Cahill Guest

    But you never hear of electricians advocating anyone going around
    An acquaintence owned a nice small old house with a fuse panel,
    probably 60 amps for the main. His insurance company refused to
    insure it. The house was supposedly torched by a meth head and he
    lost everything.


    Bret Cahill
     
  11. Mr Ron

    Mr Ron Guest

    If you read the above text, we had to derate the circuit from 32A to 16 Amp
    as the resistance of the circuit was too great for anything above a 16A
    breaker to trip in the required time. Wiring otherwise tested OK.
    That's the point, CB was FAULTY & not testable.

    Ron
     
  12. Bret Cahill

    Bret Cahill Guest

     We eventually found the breaker at the other side of the store & had
    It seems like it was "over fused" or "over breakered" but how do you
    know it was faulty if there was no test to determine if it was faulty?

    Apparently you had _some_ test to determine if it was faulty.


    Bret Cahill
     
  13. Bret Cahill

    Bret Cahill Guest

    How many times can you flip a 30 Amp CB on and off before it wears
    No insult was intended nor should be taken.

    Some people do everything on spec and some people occasionally do
    things off spec.

    And some will try to turn off spec into a religion. The more gnarly
    the better. President Obama is not one of those people.
    A retired electrician just told me there was no way to damage CBs by
    flipping them like switches.


    Bret Cahill
     
  14. Mr Ron

    Mr Ron Guest

    They have a rated time/load curve. As the load increases the trip time is
    reduced which is why you can load them to the max current rating. The cable
    resistance is measured to to give an Earth Fault Current figure that would
    trip the CB within 0.4 seconds. If the Live/Earth resistance is too high
    for the breaker it won't trip fast enough.

    Ron
     
  15. that sucks, but at least he didn't get ripped off by the insurance
    company.
     
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