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saw triggering breaker

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  • Noitoen
    replied
    Originally posted by dian View Post
    you mean i dive into that breaker box. never! so you mean to check if the rcd is defective? very unlikely, they are high quality components about 10 years old.
    No. I didn't mean any hard wiring. I meant that you find an outlet serviced by the other RCD just to make sure. 10 years or 1 year, even on high quality equipment does't mean a thing. Components simply fail.

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  • dian
    replied
    you mean i dive into that breaker box. never! so you mean to check if the rcd is defective? very unlikely, they are high quality components about 10 years old.

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  • Noitoen
    replied
    Originally posted by dian View Post
    you mean to plug it in somewhere else? no, all wall sockets in that area go to the same breaker and rcd. i could wire it to a ceiling light. that would be another breaker but still the same rcd. what is your idea?
    You have the F20 and F30 rcd circuits. You could get an extension cord to try the other circuit temporarily.

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  • dian
    replied
    you mean to plug it in somewhere else? no, all wall sockets in that area go to the same breaker and rcd. i could wire it to a ceiling light. that would be another breaker but still the same rcd. what is your idea?

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  • Noitoen
    replied
    Originally posted by dian View Post
    yes, its my understanding this has no overcurrent function. there are three 40 amp breakers outside of the house. i run several vfds with no problems. also the high frequency start from the welder (closer to the box than the saw) is no problem. the rcd tripps about every second time the saw stalls. at that time of the day there is usually little load connected. lights, heater, toasters, watter kettle and hairdryiers are off, as well as the heat pump.
    Have you tried another plug from another breaker?

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  • dian
    replied
    yes, its my understanding this has no overcurrent function. there are three 40 amp breakers outside of the house. i run several vfds with no problems. also the high frequency start from the welder (closer to the box than the saw) is no problem. the rcd tripps about every second time the saw stalls. at that time of the day there is usually little load connected. lights, heater, toasters, watter kettle and hairdryiers are off, as well as the heat pump.

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  • J Tiers
    replied
    The markings tend to indicate the RCD is OK with half wave current, but how far that goes is not clear.

    However the fault seems to be associated with the saw jamming. I am not sure how that affects the current balance, other than causing a much higher current and possibly causing a trip per my item 3 suggestion.

    The fact that the RCD is rated to 40A indicates that it has to operate correctly up to at least 40A. But it may not necessarily operate correctly above 40A, and the existing load plus the stalled motor current probably goes over 40A. It is rated to open the contacts up to a considerably higher current, but that does not mean the RCD part operates right at over 40A.

    Originally posted by MattiJ View Post
    4. part of the return current on neutral wire goes to somewhere it shouldn't. (some fool connecting ground and neutral)
    In other words, an actual ground fault......per item 1. But why only when the saw jams?

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  • PStechPaul
    replied
    Another possibility might be some appliance that uses a single wave rectifier, which causes some DC to flow through the circuit. At some point this may cause saturation of the differential transformer and a shifted or distorted waveform. This should cancel out if the same DC flows in both windings, but it may have some effect. Also, a DC component might cause magnetization of the motor. This can also happen if current flow is abruptly stopped at a peak value, and then very high current can flow when re-energized, due to remanent magnetism. This also occurs in transformers.

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  • MattiJ
    replied
    4. part of the return current on neutral wire goes to somewhere it shouldn't. (some fool connecting ground and neutral)

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  • J Tiers
    replied
    Originally posted by MattiJ View Post
    Like Noitoen mentioned this is not a combination breaker, only RCD without overcurrent function. Really common way to install things here in Europe.

    For example we have
    powerco-->3x35A ceramic fuses -->30mA RCB(40A)s --> 16/10A branch circuit breakers
    OK, I'll believe that as you seem to know it for sure.

    The specs in translation appeared to show the combo, which we have commonly in US. (the constant 40A over temp can be consistent with that also, most overcurrent breakers have a temperature dependence, although a magnetic type has much less than a thermal type, and tends to be a fast trip unless a delay feature is added. German perfection=magnetic better)

    That only makes the mystery worse. Now you must explain how it trips with no fault.

    The only explanations seem to be

    1) there IS a ground fault

    2) The breaker is defective

    3) There IS a (possibly unintended) combi feature through the excess current actually triggering the imbalance function through inherent imperfection in the balance.

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  • MattiJ
    replied
    Originally posted by J Tiers View Post

    If it is a non-time delay breaker, which the specs on the 40A seem to suggest, and a smaller one following it is a time-delay type, then it CAN open right through the smaller breaker. The time delay on the smaller breaker can allow a larger current for enough time to open even the larger rated one, IF the larger one is not a time delay.

    If, as seems to be the case, there are other things on the circuits supplied by the 40A combination breaker, then the amount of added current from an overload would not need to be as much. The "base amount" of current for the other devices subtracts from the amount the 40A breaker can carry, so that it is easier to cause it to open on some sort of overload.

    .
    Like Noitoen mentioned this is not a combination breaker, only RCD without overcurrent function. Really common way to install things here in Europe.

    For example we have
    powerco-->3x35A ceramic fuses -->30mA RCB(40A)s --> 16/10A branch circuit breakers

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  • PStechPaul
    replied
    I had been under the impression that a residential GFCI or RCD outlet would be set to trip at about 30 mA, but that may be the maximum current through the human body that is considered "safe". But the references I found indicate that it is usually 5 mA. Here is a fairly detailed analysis of GFCI design, including a circuit diagram. A few years ago I had a problem with a laundry appliance tripping the GFCI outlet, and IIRC I determined the trip point to be about 20 mA, using a resistor decade box from line to earth ground. I posted a thread here, but I haven't searched for it yet. Another thing to consider is that the differential current transformer is not perfect, and may output a small percentage of the total current due to unequal coupling of the windings to the core, and this may cause an increase of sensor current at higher currents.

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  • J Tiers
    replied
    Originally posted by Noitoen View Post
    That beaker in particular will not trip on an overload. 40A is the contact carrying capacity. 0.03A on the other end is too sensitive and most input filters will cause it to trip especially VFD and SMPSUs
    If it is a non-time delay breaker, which the specs on the 40A seem to suggest, and a smaller one following it is a time-delay type, then it CAN open right through the smaller breaker. The time delay on the smaller breaker can allow a larger current for enough time to open even the larger rated one, IF the larger one is not a time delay.

    If, as seems to be the case, there are other things on the circuits supplied by the 40A combination breaker, then the amount of added current from an overload would not need to be as much. The "base amount" of current for the other devices subtracts from the amount the 40A breaker can carry, so that it is easier to cause it to open on some sort of overload.

    Per the RCD function.....The 30 mA type is about 10x LESS sensitive as an RCD than the standard "outlet mounted" type in the US, which trips on a mismatch of 0.0035A (3.5 mA). So it should be difficult to cause it to open due to a "leakage" current, or whatever is drawn by one or more input filters, etc. Most normal devices do not cause the US type to open, although they can be a problem if there are a number of computers, etc plugged in. That is one reason why they are used on individual outlets.

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  • MattiJ
    replied
    Originally posted by Noitoen View Post
    When more than one GF breaker is used in a distribution board you must make sure that you don't mix the neutral wires otherwise you can get it to trip without any apparent reason.
    Ground and neutral connected somewhere after the circuit panel would also cause GFCI tripping and it would be depend on load current.

    I'm not sure about Swiss requirements but at least in here it was allowed earlier to do neutral+live wiring to sockets and connect jump wire between neutral and ground in the socket.
    Causes all kind of funny problems like tripping GFCI's and putting 2A current trough television antenna coax cable.

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  • MattiJ
    replied
    Originally posted by Noitoen View Post
    That beaker in particular will not trip on an overload. 40A is the contact carrying capacity. 0.03A on the other end is too sensitive and most input filters will cause it to trip especially VFD and SMPSUs
    Larger VFD yes but household switch mode power supplies hardly ever trigger 30mA A-type GFCI.

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