Discuss Max Permitted Zs for 3036 semi enclosed rewirable fuse... in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

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I'm just hoping I can cross reference my knowledge or be corrected by someone on a quick query. It's a test question I'm doing but I'm querying the answer I've been given.

I want to find the Max permitted Zs on a 3036 45A fuse. I was under the impression that I should reference table 41.2 in the regs for the max permitted Zs value if the circuit is a final circuit (rather than a distribution circuit), and the system is not a TT. The answer I've been given has sent me to table 41.4, for a 5 sec disconnection time rather than a 0.4 sec disconnection time. Is there any other reason why the answer may be sending me to the 5 sec disconnection time table rather than the 0.4 sec table (other than the two points I've mentioned above)?

Any help would as always be massively appreciated.

Thanks again.
 
At 45a it is usually fixed resistive loads and not socket circuits or lights at 32a and 6a among other values. Hence the 5s permissible time as I understand if that is what you are getting at?
 
Hi - looking at Fig 3A2(b) a 45A BS3036 fuse needs 390A to melt in 0.4 seconds, if that’s the disconnection time needed. So using 0.8(temp) x 230V x 0.95 (Cmin) / 390A, I got 0.45 Ohms as the max test value.

Edit - which of course isn’t your question really, but @haptism has it I reckon :) .
 
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