gkenyon:ProMbrooke:
Thats where CPCs come in, in that they would cause the fuse or MCB to open in 0.2 seconds or less.Doesn't that happen anyway ... in TN systems where the loop impedance ensures operation in 0.1 s?
The issue being, that, in TN-S systems (no RCD), you're limited in circuit length with Type C mcb's.
Also, interested where 25 V comes into the equation here? To do that, you've got to oversize the cpc, not undersize it ... and even then, may not be possible in TN-S due to the effect of the distributor's cpc ?
It does, but going by table 41.1 we are allowed a loop Z high enough to cause 0.4 seconds disconnection.
Type A, B, or C MCBs, fuses, or the like you are always limited in circuit length be it voltage drop or should the RCD become inoperative.
25 volts is the highest touch voltage under infinite time allowed by the IEC in wet locations according to Table C.1 in IEC 61200-413. Where higher touch voltage are found, disconnection is required. At 125 volts 0.17 seconds is required. With a reduced size CPC, even faster times are required.
gkenyon:ProMbrooke:
Thats where CPCs come in, in that they would cause the fuse or MCB to open in 0.2 seconds or less.Doesn't that happen anyway ... in TN systems where the loop impedance ensures operation in 0.1 s?
The issue being, that, in TN-S systems (no RCD), you're limited in circuit length with Type C mcb's.
Also, interested where 25 V comes into the equation here? To do that, you've got to oversize the cpc, not undersize it ... and even then, may not be possible in TN-S due to the effect of the distributor's cpc ?
It does, but going by table 41.1 we are allowed a loop Z high enough to cause 0.4 seconds disconnection.
Type A, B, or C MCBs, fuses, or the like you are always limited in circuit length be it voltage drop or should the RCD become inoperative.
25 volts is the highest touch voltage under infinite time allowed by the IEC in wet locations according to Table C.1 in IEC 61200-413. Where higher touch voltage are found, disconnection is required. At 125 volts 0.17 seconds is required. With a reduced size CPC, even faster times are required.
