max zs of large fuses

peterhardacher · Apr 10, 2013

BS7671 tables only go to certain size fuses eg how can I find max ZS of 400 amp BS88 - 2 on niceic test sheets they ask for a max value out of regs table I have only managed to find a busman fuse chart which differs been told by employer to use these values on sheets any input would help thanks

Silly Sausage · Apr 10, 2013

I'll say this only once...
Use the manufacturers data.

peterhardacher · Apr 10, 2013

ThAnks struggling to get such information though that's what I been using but only got busman available and don t get any time to search for such info the boss gave me this info

cobrauk · Apr 10, 2013

Bussmann gG fuses to BS 88: Parts 2 and 6 are:
Rating (A) Zs (Ohms) Rating (A) Zs (Ohms) Rating (A) Zs (Ohms)
6 14 50 1.1 250 0.16
10 7.7 63 0.86 315 0.13
16 4.3 80 0.60 400 0.096
20 3.0 100 0.44 500 0.073
25 2.4 125 0.35 630 0.054
32 1.9 160 0.27 800 0.0

MEM state 400amp BS88 part 2 & 6 is 0.094 so they are about the same m8

Guitarist · Apr 10, 2013

Use generic test sheets, which don't ask for a maximum.

Engineer54 · Apr 10, 2013

peterhardacher said:
BS7671 tables only go to certain size fuses eg how can I find max ZS of 400 amp BS88 - 2 on niceic test sheets they ask for a max value out of regs table I have only managed to find a busman fuse chart which differs been told by employer to use these values on sheets any input would help thanks

Mores the point, do you have test equipment that can test to those low values?? Which brings us back to another threads discussion, on the need for HR test equipment!! lol!!

Knobhead · Apr 10, 2013

I love this subject, it’s so woolly.

I’ve had heavy faults where the fuse has survived and the upstream protection has gone first. Others where the fault let through was to great for the fuse and its not contained the fault.
I had nothing to do with the design of the systems, I inherited them “as is” and was stuck with them.

Never had a 1600A fuse blow and I’m glad of that. The 11KV protection picked it up first every time. The biggest fuse I’ve dealt with was 3200A.

peterhardacher · Apr 10, 2013

Thanks for the reply very helpfull and no my meters provided cannot read such low values I was discussing this with one of the lads the other day that normal meters are not acurate below 0.01 ohms I think this is correct and to be honest this was the first I had heard of this ( hopefully not sounding stupid. ) I have been provided with niceic sheets not very industrial friendly in my opinion . Thank god for smart phones eh what a handy app this is when ya need to ask some advice as the boss will tell ya anything to get them sheets. Signed lol