Malcolm Stewart wrote:
wrote in message
ups.com...
Andrew Gabriel wrote:

Leads up to 12m long must be 1.25mm² conductors.
Leads up to 15m long must be 1.5mm² conductors.
Leads up to 25m long must be 2.5mm² conductors (which won't fit
into a standard 13A plug).

in each of the above cases, why?

To ensure that the overall loop resistance is low enough for the fuse to
blow quickly in the event of a fault.

From CRC Handbook of Chemistry and Physics, 77th edition, 1996-1997,
2.588 mm^2 copper wire is 0.00319 ohms per metre. 25m x 2 x 0.00319 =
0.152 ohms. So theres no way that 25m of 2.5mm^2 would have any
noticeable effect on fuse or mcb action, ditto for 25m of 1.5mm^2.

0.152 ohm drops 1.99v at 13A, so v drop is still ok with wire half that
size.


NT