Help needed please

[Chris Autey]

Hello everyone I'm new here and currently stuck with some homework!

Basically the question is:
What is the In for a BS 88 fuse from table 41.2 with an Ib of 15A?

Ive found the tables in my regs book but can't make head nor tale of it could somebody kindly explain to me how to do this in simple terms so I can understand lol cos its doing my head in not knowing what's going off and I feel I'm missing the obvious.

many thanks

 

[i=p/u]

Well (Ib) is your design current of 15A now you need a protective device (In) equal or greater , if you go back to the table 41.2 what size of protective device is equal or greater

 

[i=p/u]

Scared to tell you answer case I'm shagged

 

[i=p/u]

Oh and welcome along..

 

[Chris Autey]

There are 4 above 15a so I could use any of the four or would they be a preference? Forgive me if I sound thick lol

 

[i=p/u]

You would normally pick the next size available , but you can use any equal or greater but then you have to consider/use bigger cables ..

 

[i=p/u]

Say you used a 32A mcb you would probably have to use 4mm or possibly 6mm depending on length of circuit .

 

[i=p/u]

In equal or greater than Ib

 

[Chris Autey]

Ha many thanks! I am finding myself thinking that stuff is harder than it actually is on my electrical journey when infact most of it really is just straight forward lol...

Thanks again

 

[i=p/u]

Good luck. What stage you at, what course you doing