2391-20 cable calcs

[shambock]

Hi

Anyone help with some cable calcs for my designe project, i must be missing something here.

Im trying to work out and show my calculations for cable sizing of a 32A ring

Length is 78 M

Number of 13A double sockets is 7

Ib is 32A
In is 32A RCBO
It should be In / Correction factors of wich i only have a grouping factor of 0.41
This makes it 32/0.41 = 78A

The above formula say that i should be using a cable capable of carrying 78A wich brings it upto 25mm ????????????? (ref meth B,singles) table 4D1A.

I know this is wrong but where am i mucking up.

Please help

 

[pushrod]

Surely, If there's room to do this, then then leaving them loose would not warrant the 0.41 derating factor in the first place?

If there were masses of space inside the trunking and you could fix the cables and guarantee the spacing there would indeed be no rating factor for grouping. But when the lid goes on can you say for certain where the cables are lying. You have to deal with the worse case scenarios. If you were using tray you could separate them easily enough and tie them

 

[johnboy6083]

If there were masses of space inside the trunking and you could fix the cables and guarantee the spacing there would indeed be no rating factor for grouping. But when the lid goes on can you say for certain where the cables are lying. You have to deal with the worse case scenarios. If you were using tray you could separate them easily enough and tie them

in trunking, i dont ever tie cables together. it makes it a pain to alter later. the only place i will tie/tape them together is in the trunking just outside of the DB, or acessory, for which you would have to pull the lid off to alter anyway. i only do this to aid identification.