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12 volt breaker malfunction

Discussion in 'Technical Discussion' started by timvail, Jun 6, 2014.

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  1. timvail, Jun 6, 2014
    #1
    timvail

    timvail Senior Member

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    On the CC yesterday and noted a 12 volt breaker was off. It controls the front bilge pump and the CO detector. Tried to turn it back to the on position but would not stay in that position. Tried it. Couple of more times and it then stayed in that position. The CO detector was working as well as the front bilge pump. I checked. Couple of hours later and the breaker was off again and would not turn on.
    1) where do I start, is this a short problem in the wiring somewhere or possibly a faulty breaker?
    Any help where to start would be helpful.
    Tks
  2. captholli, Jun 6, 2014
    #2
    captholli

    captholli Senior Member

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    If you have a clamp on Amp meter use it to see how much DC amp draw you have on the breaker when under current load. If when the pump and CO detector are off and not drawing any current AND your breaker wont stay in the on position than more than likely you have a weak breaker. Another way to test this is to take your circuit to another DC breaker in the panel of the same amp. rating and see if it holds.
  3. NYCAP123, Jun 6, 2014
    #3
    NYCAP123

    NYCAP123 Senior Member

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    In the old days I seem to remember we put a penny behind the fuses. Of course houses tended to burn down.:eek: Find the cause. I suspect that your float switch may have gotten hung up and the bilge pump overheated. Start there.
  4. timvail, Jun 6, 2014
    #4
    timvail

    timvail Senior Member

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    12 volt breaker

    Ok, arrived at boat and turned the breaker back on. Everything works fine now.
    Moved the leads to another breaker same amperage and co detector and pump work fine. Moved other leads to the suspect breaker and those items work fine too. Float switch appears to work ok. Perhaps I should just install a new breaker and see if problem comes back?
  5. NYCAP123, Jun 6, 2014
    #5
    NYCAP123

    NYCAP123 Senior Member

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    I'd be more inclined to not replace the breaker, but instead see if the situation returns and then go after the cause rather than just flipping the breaker until the line cools enough to allow it to hold. If it was a float switch hanging up you may find that it needs to be moved and the pump replaced.
  6. timvail, Jun 6, 2014
    #6
    timvail

    timvail Senior Member

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    12volt breaker

    Ok, thanks for the advice. Have cleaned around the float switch and pump to make sure no forien material is present. Also checked the pump to make sure nothing hung up in it. Will monitor the breaker and see if it stays on.
    Tks again
  7. bobhorn, Jun 6, 2014
    #7
    bobhorn

    bobhorn Member

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    Put an amp meter on the circuit and be sure. There may be a short in the wiring somewhere. The only sure way to see if the breaker is bad is to measure the actual current. Everything else is guess work.

    Bob
  8. timvail, Jun 6, 2014
    #8
    timvail

    timvail Senior Member

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    Borrowed a clamp on meter. Turned pump on manually and amp draw well within perimeters. This pump rarely comes on as is located in a dry area.
    The co detector draws next to nothing.
  9. Chasm, Jun 6, 2014
    #9
    Chasm

    Chasm Senior Member

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    Sounds more like an overload than a short.

    Breakers usually have two mechanisms can that trip them.
    1) Magnetic, this is very fast but needs quite a bit of current. Trips in milliseconds when shorted or in serve overloads, where time is essential.
    2) Thermal, this does not need much over current but takes time. Trips in overloads but will take seconds, probably minutes, even up to an hour.

    Fuses obviously only have the thermal mechanism.

    Don't get the wrong impression, if the current get really high fuses will also trip in milliseconds.
    The advantage of the magnetic system is that you can trip very fast even in relatively light overloads. The threshold depends on type and trip characteristic of the breaker. For a typical European B type breaker the allowable lower threshold for magnetic tripping is between 3 and 5 times the rating.


    What does that mean in your case?
    Breakers have a ream lockout. If thermal trigger tripped it has to cool down before it can be reset.
    (Depending on the type of breaker it may feel that comparatively little force is necessary to reset the breaker while the thermal lockout is active.)

    So the next step would be to measure current in this circuit, while the pump is running, under load. (-> A few buckets of water) That will determine if there is too much current or a breaker defect.

    If there is too much current do not just replace the breaker! Circuit breakers are sized to protect the wire. Overloading wires is spelled: Electrical Fire
    A bit dramatic but a real possibility. Esp. if you don't know if there are any changes of wire size on the run to the pump.

    Edit: Oops, wrote this without reading the last post.
    The CO detector should draw next to nothing, so that's as expected.
    Did you test the pump with or without water? Without draws less current.