GN3 formula confusion...mistake?

[swaRRR]

For continuity of ring final conductors it says we can use the r1 to check the expected result for r2, and gives the following formula to use:

r2 = (1/ csa of cpc) / (1/ csa of line) x r2 = (csa of line / csa of cpc) x r2.

Shouldn't the bold r2's say r1? After all we can't use an unknown to calculate itself, surely? Or am i being thick again?

 

[SparkyChick]

approximate r2 = (csa of live conductors / csa of CPC) x r1

 

[swaRRR]

approximate r2 = (csa of live conductors / csa of CPC) x r1

Thanks so the book has an error in it. Not best pleased considering how expensive it is.

 

[loz2754]

Thanks so the book has an error in it. Not best pleased considering how expensive it is.

I've just checked and it would seem you are correct.

 

[swaRRR]

I've just checked and it would seem you are correct.

Let me tell you as a beginner to testing it confused me. I'm not the greatest at maths but i do know Y = result x Y doesn't jive.

 

[davesparks]

Thanks so the book has an error in it. Not best pleased considering how expensive it is.

They always have errors in, a few years ago the on-site guide listed the current rating of 6mm T&E as 2A

 

[swaRRR]

They always have errors in, a few years ago the on-site guide listed the current rating of 6mm T&E as 2A