If i have...
3 phases
70mm cables
120 Amps
BS88s
....feeding a busbar chamber
and then coming off the busbar in 25mm, single phase, to feed a switch fuse of 60/80/100 amp rating ... all run in steel trunking, all singles cables, all cable entries protect cables with paxelin(spelling?)
the 25mm is protected against overload by the 60/80/100 SwFuse
but 25mm can only take ~101amps single phase, ~89amps 3 phase if a fault occured on the cable between SwFuse and Busbar
Would this be ok as the fault is very unlikely to happen amd a fault would blow the 120amp BS88 in very little time (so long as earth loops are good enough)... or is this not allowed ?
I would use the single phase current carrying capacity value, as only one phase feeds each of the SwFuses, right ?
any info appreciated
3 phases
70mm cables
120 Amps
BS88s
....feeding a busbar chamber
and then coming off the busbar in 25mm, single phase, to feed a switch fuse of 60/80/100 amp rating ... all run in steel trunking, all singles cables, all cable entries protect cables with paxelin(spelling?)
the 25mm is protected against overload by the 60/80/100 SwFuse
but 25mm can only take ~101amps single phase, ~89amps 3 phase if a fault occured on the cable between SwFuse and Busbar
Would this be ok as the fault is very unlikely to happen amd a fault would blow the 120amp BS88 in very little time (so long as earth loops are good enough)... or is this not allowed ?
I would use the single phase current carrying capacity value, as only one phase feeds each of the SwFuses, right ?
any info appreciated