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Determining device designation of rewirable fuses

Farmboy
Table 3.1 of GN6 lists the rated short cct capacity for three BS 3036 device designations (S1A, S2A & S4A). But how do you determine the designation of the device?


On a different note, on an eicr, would you give a C2 to a size that was lower than the PEFC or PSCC at the point of use? I've looked in BPG4 and codebreakers but couldn't see anything relating specifically to breaking capacity (sorry if I've missed it).


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    Agree, and the safe course is to assume anything unmarked is the lowest category -s1 = 1000Amps. If your pssc at the board is more than this, then there is a risk if there is a fault close to the board, if the fault is not cleared before refitting the fuse holder.

    The board will not blow off the wall or anything like that, we are not talking mega joules !  **

    Nor will the ceramic crack, but there is a risk of burns to someone replacing a fuse, if the fault is very low impedance and not cleared.  (though if the fault is just 10m along some 2.5mm T &E that extra impedance will significantly reduce the fault current and the risk) Take great care to identify and fix the fault before replacing the fuse wire.

    regards

    Mike



    **As an aside, even if supply side PSSC was infinite,  the energy would be limited to the resistance of the fuse wire -at most a few milliohm - times the I2t of either this fuse or the company fuse which ever blows first. I2t is not normally quoted for BS3036 fuses but you can estimate it from the I/t curves.)

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  • 0
    Agree, and the safe course is to assume anything unmarked is the lowest category -s1 = 1000Amps. If your pssc at the board is more than this, then there is a risk if there is a fault close to the board, if the fault is not cleared before refitting the fuse holder.

    The board will not blow off the wall or anything like that, we are not talking mega joules !  **

    Nor will the ceramic crack, but there is a risk of burns to someone replacing a fuse, if the fault is very low impedance and not cleared.  (though if the fault is just 10m along some 2.5mm T &E that extra impedance will significantly reduce the fault current and the risk) Take great care to identify and fix the fault before replacing the fuse wire.

    regards

    Mike



    **As an aside, even if supply side PSSC was infinite,  the energy would be limited to the resistance of the fuse wire -at most a few milliohm - times the I2t of either this fuse or the company fuse which ever blows first. I2t is not normally quoted for BS3036 fuses but you can estimate it from the I/t curves.)

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