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.
 
T

The Ghost

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?
 

Wilko

-
Arms
Esteemed
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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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
See 411.3.2.2 & table 41.4

If the rated current of the circuit in question exceeds

ii) 32 A supplying only fixed connected current using equipment
 

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