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IEC 60364 Table 48A

Former Community Member
Former Community Member
Does anyone know where I can find table 48A? I am reading of its existence, but don't know where to find it.
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  • Former Community Member
    0 Former Community Member
    Right, there will be huge difference in potential. Thats where 0.25 seconds come in, in that harm can not take place with 125 volts between the hands or hands and feet persisting for only a fraction of a second. 


    IF the fault is through a heating element, the resistive divider math still applies. A 20 amp type B  MCB has an EFLI of 1.84 ohms. Assuming an R1+R2 of 1.49, we have an R2 of 0.745.  4000/230=17 amps or a 13 ohm resistance. Assuming the fault is at midway through the element, 6.5 ohms plus 0.745 ohms = 7.245 ohms. Using a resistive divider, we get 21.4 volts to remote earth.


    Assuming that the fault takes 5 seconds to trip the MCB, 4 x 20= 80 amps or a 2.875 ohm fault.


    0.745ohms + 2.875 ohms = 3.62 ohms. Going by a resistive divider we get 39 volts to remote earth. Below 50 volts, but higher than 25 volts. RCD would help in this case, but so does the full size CPC.



       

    Typically a dead fault would trip an MCB instantly, so the RCD is supplemental protection as it should be. However if fuses are fitted 0.4 seconds would end up being a real thing. 


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  • Former Community Member
    0 Former Community Member
    Right, there will be huge difference in potential. Thats where 0.25 seconds come in, in that harm can not take place with 125 volts between the hands or hands and feet persisting for only a fraction of a second. 


    IF the fault is through a heating element, the resistive divider math still applies. A 20 amp type B  MCB has an EFLI of 1.84 ohms. Assuming an R1+R2 of 1.49, we have an R2 of 0.745.  4000/230=17 amps or a 13 ohm resistance. Assuming the fault is at midway through the element, 6.5 ohms plus 0.745 ohms = 7.245 ohms. Using a resistive divider, we get 21.4 volts to remote earth.


    Assuming that the fault takes 5 seconds to trip the MCB, 4 x 20= 80 amps or a 2.875 ohm fault.


    0.745ohms + 2.875 ohms = 3.62 ohms. Going by a resistive divider we get 39 volts to remote earth. Below 50 volts, but higher than 25 volts. RCD would help in this case, but so does the full size CPC.



       

    Typically a dead fault would trip an MCB instantly, so the RCD is supplemental protection as it should be. However if fuses are fitted 0.4 seconds would end up being a real thing. 


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