17th edition Can't find it in the book? help please.

[ChristianG]

Hi people

Just starting to do the 17th edition course.

Trying to find in the book bs7671 , the answer to a very simple question. I believe that actually knowing the answer and where it is to be found in the book will help me pass the course.

Heres the question>>>>

A 230V circuit is protected by a 20A type B circuit-breaker to BS EN 60898. The minimum value of fault current to ensure compliance with maximum disconnection times is:

Don't need the answer just where can I find it in the 17th edition book. I've looked in part 4, the contents page the index. can't find the answer.


Any help or pi$$ taking gratefully recieved

 

[Mac]

Table 41.1 of BS 7671.Table 2,Page 22

 

[ChristianG]

Hi Mac
Thanks for your help

But table 41.1 is on page 46 of the 17th edition bs 7671 book and is for maximum disconnection times. I still cannot find it. I think I need a brain transplant.

 

[Notsosmart]

After noting that required trip time is 0.4 secs from the afor mentioned table then go to Appendix 3 Time~current characteristics, go to page 249 run your finger along 0.4mS until you hit the 20A breaker curve; that will give you the minimum fault current to trip (100A)

 

[ChristianG]

Thank you notsosmart for pointing that out to me.
I now have learnt to pay attention to the appendices as well as the parts to look for the answers. I got into the flow of just looking at the part for that set of questions.

Thanks to you both for the input.

I was told to presume that the questions are in order of the parts. I think i might just rely on knowing which part to go to, to find the answer

 

[Notsosmart]

My pleasure,

The thing to remember is that exam question setters try to be clever & mix things up so (as in the example you gave) a fairly straight forward question becomes a bit of pain to extrapolate exactly what & where to find the answer.

Good luck with the course & Exam.

Throw a few more example qustions at the forum its good to keep the grey matter churning