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V.High PFC at switchfuse

Horace Horace
Hello guys

I was looking at a job today at an old house divided into flats where a BS 88 dist board supplies my switch fuse with 60A (which is adjacent to it). The switch fuse is a dated MEM with a porcelain 60A BS3036 but looks in fair condition. Im getting 0.01 ohms ze at the switch fuse and due to this the PFC is off the scale.

Am i right in contemplating that as its a single phase supply under 100a, that the switchfuse's 60A rewireable 3036 breaking capacity can be overlooked as the upstream BS88 will take the brunt of any potential fault and let through no more than 3-4KA which the rewireable can then handle. While were on the topic of breaking capacity's, anyone know the BC of a ceramic MEM 60A 3036 ? I do need to record a suitable PFC value at the switch fuse, my multi tester is is reading 19.9KA (which likely calculates as off the scale). The PFC of the CU in the flat is an easier 3.5KA !


Thanks all



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    Thanks for response guys, the switchfuse is a metal one which needs to be switched off before the cover can be removed therefore no chance of inserting a fuse in onto a fault. As s kindly pointed out, any explosions due to a future fault will be limited by the metal housing so I guess its deemed as safe for continued operation.. Nevertheless I will still need to record the breaking capacity of the switchfuse on a certificate and im not sure what value to enter ?? The BS88 fuse supplying the switchfuse will likely limit the fault current but to what value im not sure; this is a good learning curve for me !


    The Ze of 0.01 is not helped by the fact that earth from the switchfuse is via the metal trunking, there is no earth cable to speak of. So I cannot disconnect any parallel paths easily. Now im contemplating the breaking capacity of the BS88 fuses that supply the switchfuses (which are also dated 1970's I think, and of porcelain) these are 500v I expect as dist board is 3ph; would BS88's of that vintage have a 80KV rating and therefore reduce the need for downstream devices to be so high. Cheers
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    Thanks for response guys, the switchfuse is a metal one which needs to be switched off before the cover can be removed therefore no chance of inserting a fuse in onto a fault. As s kindly pointed out, any explosions due to a future fault will be limited by the metal housing so I guess its deemed as safe for continued operation.. Nevertheless I will still need to record the breaking capacity of the switchfuse on a certificate and im not sure what value to enter ?? The BS88 fuse supplying the switchfuse will likely limit the fault current but to what value im not sure; this is a good learning curve for me !


    The Ze of 0.01 is not helped by the fact that earth from the switchfuse is via the metal trunking, there is no earth cable to speak of. So I cannot disconnect any parallel paths easily. Now im contemplating the breaking capacity of the BS88 fuses that supply the switchfuses (which are also dated 1970's I think, and of porcelain) these are 500v I expect as dist board is 3ph; would BS88's of that vintage have a 80KV rating and therefore reduce the need for downstream devices to be so high. Cheers
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